source: opengl-game/new-game.cpp@ dc19a39

#include "logger.h"

#include "stb_image.h"

// I think this was for the OpenGL 4 book font file tutorial
//#define STB_IMAGE_WRITE_IMPLEMENTATION
//#include "stb_image_write.h"

#define _USE_MATH_DEFINES

#include <glm/mat4x4.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include "IMGUI/imgui.h"
#include "imgui_impl_glfw_gl3.h"

#include <GL/glew.h>
#include <GLFW/glfw3.h>

#include <cstdio>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <fstream>
#include <sstream>
#include <cmath>
#include <string>
#include <array>
#include <vector>
#include <queue>
#include <map>

using namespace std;
using namespace glm;

enum State {
   STATE_MAIN_MENU,
   STATE_GAME,
};

enum Event {
   EVENT_GO_TO_MAIN_MENU,
   EVENT_GO_TO_GAME,
   EVENT_QUIT,
};

enum ObjectType {
   TYPE_SHIP,
   TYPE_ASTEROID,
   TYPE_LASER,
   TYPE_EXPLOSION,
};

enum AttribType {
   ATTRIB_UNIFORM,
   ATTRIB_OBJECT_VARYING,
   ATTRIB_POINT_VARYING,
};

// Add more types as I need them
enum UniformType {
   UNIFORM_NONE,
   UNIFORM_MATRIX_4F,
   UNIFORM_1F,
   UNIFORM_3F,
};

enum UIValueType {
   UIVALUE_INT,
   UIVALUE_DOUBLE,
};

struct SceneObject {
   unsigned int id;
   ObjectType type;

   // Currently, model_transform should only have translate, and rotation and scale need to be done in model_base since
   // they need to be done when the object is at the origin. I should change this to have separate scale, rotate, and translate
   // matrices for each object that can be updated independently and then applied to the object in that order.
   // TODO: Actually, to make this as generic as possible, each object should have a matrix stack to support,
   // for instance, applying a rotate, then a translate, then another rotate. Think about and implement the best approach.
   mat4 model_mat, model_base, model_transform;
   mat4 translate_mat; // beginning of doing what's mentioned above
   unsigned int num_points;
   GLuint vertex_vbo_offset;
   GLuint ubo_offset;
   vector<GLfloat> points;
   vector<GLfloat> colors;
   vector<GLfloat> texcoords;
   vector<GLfloat> normals;
   bool deleted;
   vec3 bounding_center;
   GLfloat bounding_radius;
};

struct Asteroid : SceneObject {
   float hp;
};

struct Laser : SceneObject {
   Asteroid* targetAsteroid;
};

struct ParticleEffect : SceneObject {
   vector<GLfloat> particleVelocities;
   vector<GLfloat> particleTimes;
};

struct EffectOverTime {
   float& effectedValue;
   float startValue;
   double startTime;
   float changePerSecond;
   bool deleted;
   SceneObject* effectedObject;

   // TODO: Why not just use an initializer list for all the instance variables
   // TODO: Maybe pass in startTime instead of calling glfwGetTime() here
   EffectOverTime(float& effectedValue, float changePerSecond, SceneObject* object)
      : effectedValue(effectedValue), changePerSecond(changePerSecond), effectedObject(object) {
      startValue = effectedValue;
      startTime = glfwGetTime();
      deleted = false;
   }
};

struct BufferInfo {
   unsigned int vbo_base;
   unsigned int ubo_base;
   unsigned int ubo_offset;
   unsigned int ubo_capacity;
};

struct AttribInfo {
   AttribType attribType;
   GLuint index;
   GLint size;
   GLenum type;
   UniformType uniType;
   GLuint buffer; // For uniforms, this is the uniform location
   size_t fieldOffset;
   GLfloat* data; // pointer to data source for uniform attributes
};

struct ShaderModelGroup {
   GLuint shaderProgram;
   GLuint vao;
   map<string, AttribInfo> attribs;
   unsigned int numPoints;
   unsigned int vboCapacity;
};

struct UIValue {
   UIValueType type;
   string label;
   void* value;

   UIValue(UIValueType _type, string _label, void* _value) : type(_type), label(_label), value(_value) {}
};

void glfw_error_callback(int error, const char* description);

void mouse_button_callback(GLFWwindow* window, int button, int action, int mods);
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods);

void APIENTRY debugGlCallback(
   GLenum source,
   GLenum type,
   GLuint id,
   GLenum severity,
   GLsizei length,
   const GLchar* message,
   const void* userParam
);

bool faceClicked(array<vec3, 3> points, SceneObject* obj, vec4 world_ray, vec4 cam, vec4& click_point);
bool insideTriangle(vec3 p, array<vec3, 3> triangle_points);

GLuint loadShader(GLenum type, string file);
GLuint loadShaderProgram(string vertexShaderPath, string fragmentShaderPath);
unsigned char* loadImage(string file_name, int* x, int* y);

void printVector(string label, vec3& v);
void print4DVector(string label, vec4& v);

void initObject(SceneObject* obj);
void addObjectToScene(SceneObject* obj,
                  map<GLuint, BufferInfo>& shaderBufferInfo,
                  map<ObjectType, ShaderModelGroup>& modelGroups,
                  GLuint ubo);
void removeObjectFromScene(SceneObject& obj, GLuint ubo);

ShaderModelGroup createModelGroup(GLuint shaderProgram);
void removeModelFromGroup(ShaderModelGroup& modelGroup, SceneObject& model);
void addModelToGroup(ShaderModelGroup& modelGroup, SceneObject& model);

void defineModelGroupAttrib(ShaderModelGroup& modelGroup, string name, AttribType attribType, GLint size, GLenum type, size_t fieldOffset);
void defineModelGroupUniform(ShaderModelGroup& modelGroup, string name, AttribType attribType, GLint size, UniformType type, GLfloat* data);
void initModelGroupAttribs(ShaderModelGroup& modelGroup);
void bindUniformData(AttribInfo& attrib);
void bindUniformData(AttribInfo& attrib, GLfloat* data);

size_t GLsizeof(GLenum);
GLvoid* getVectorAttribPtr(SceneObject& obj, size_t attribOffset);
GLvoid* getScalarAttribPtr(SceneObject& obj, size_t attribOffset);

void calculateObjectBoundingBox(SceneObject* obj);

void initializeParticleEffectBuffers(map<GLuint, BufferInfo>& shaderBufferInfo,
                  map<ObjectType, ShaderModelGroup>& modelGroups,
                  GLuint ubo);

void populateBuffers(vector<SceneObject*>& objects,
                  map<GLuint, BufferInfo>& shaderBufferInfo,
                  map<ObjectType, ShaderModelGroup>& modelGroups,
                  GLuint ubo);

void copyObjectDataToBuffers(SceneObject& obj,
                  map<GLuint, BufferInfo>& shaderBufferInfo,
                  map<ObjectType, ShaderModelGroup>& modelGroups,
                  GLuint ubo);

void transformObject(SceneObject& obj, const mat4& transform, GLuint ubo);

// TODO: instead of using these methods, create constructors for these
SceneObject* createShip();
Asteroid* createAsteroid(vec3 pos);
Laser* createLaser(vec3 start, vec3 end, vec3 color, GLfloat width);
ParticleEffect* createExplosion();

void translateLaser(Laser* laser, const vec3& translation, GLuint ubo);
void updateLaserTarget(Laser* laser, vector<SceneObject*>& objects, ShaderModelGroup& laserSmg, GLuint asteroid_sp);
bool getLaserAndAsteroidIntersection(vec3& start, vec3& end, SceneObject& asteroid, vec3& intersection);

void renderMainMenu();
void renderMainMenuGui();

void renderScene(map<GLuint, BufferInfo>& shaderBufferInfo,
                  map<ObjectType, ShaderModelGroup>& modelGroups, GLuint ubo);

void renderSceneGui(map<string, vector<UIValue>> valueLists);

void initGuiValueLists(map<string, vector<UIValue>> valueLists);
void renderGuiValueList(vector<UIValue>& values);

float getRandomNum(float low, float high);

#define NUM_KEYS (512)
#define ONE_DEG_IN_RAD ((2.0f * M_PI) / 360.0f) // 0.017444444 (maybe make this a const instead)
#define TARGET_FPS 60.0f

const int KEY_STATE_UNCHANGED = -1;
const bool FULLSCREEN = false;
const int EXPLOSION_PARTICLE_COUNT = 300;
unsigned int MAX_UNIFORMS = 0; // Requires OpenGL constants only available at runtime, so it can't be const

int key_state[NUM_KEYS];
bool key_down[NUM_KEYS];

int width = 640;
int height = 480;

vec3 cam_pos;

mat4 view_mat;
mat4 proj_mat;

vector<SceneObject*> objects;
queue<Event> events;
vector<EffectOverTime*> effects;

SceneObject* clickedObject = NULL;
SceneObject* selectedObject = NULL;

float NEAR_CLIP = 0.1f;
float FAR_CLIP = 100.0f;

// TODO: Should really have some array or struct of UI-related variables
bool isRunning = true;

ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

Laser* leftLaser = NULL;
EffectOverTime* leftLaserEffect = NULL;

Laser* rightLaser = NULL;
EffectOverTime* rightLaserEffect = NULL;

SceneObject* objExplosion;

map<string, vector<UIValue>> valueLists;

/*
* TODO: Asteroid and ship movement currently depend on framerate, fix this in a generic/reusable way
* Disabling vsync is a great way to test this
*/

int main(int argc, char* argv[]) {
   cout << "New OpenGL Game" << endl;

   if (!restart_gl_log()) {}
   gl_log("starting GLFW\n%s\n", glfwGetVersionString());

   glfwSetErrorCallback(glfw_error_callback);
   if (!glfwInit()) {
      fprintf(stderr, "ERROR: could not start GLFW3\n");
      return 1;
   }

#ifdef __APPLE__
   glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
   glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
   glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
   glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#else
   glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
   glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
#endif

   GLFWwindow* window = NULL;
   GLFWmonitor* mon = NULL;

   glfwWindowHint(GLFW_SAMPLES, 16);
   glfwWindowHint(GLFW_OPENGL_DEBUG_CONTEXT, true);

   if (FULLSCREEN) {
      mon = glfwGetPrimaryMonitor();
      const GLFWvidmode* vmode = glfwGetVideoMode(mon);

      width = vmode->width;
      height = vmode->height;
      cout << "Fullscreen resolution " << vmode->width << "x" << vmode->height << endl;
   }
   window = glfwCreateWindow(width, height, "New OpenGL Game", mon, NULL);

   if (!window) {
      fprintf(stderr, "ERROR: could not open window with GLFW3\n");
      glfwTerminate();
      return 1;
   }

   glfwMakeContextCurrent(window);
   glewExperimental = GL_TRUE;
   glewInit();

   if (GLEW_KHR_debug) {
      cout << "FOUND GLEW debug extension" << endl;
      glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS);
      glDebugMessageCallback((GLDEBUGPROC)debugGlCallback, nullptr);
      cout << "Bound debug callback" << endl;
   } else {
     cout << "OpenGL debugg message callback is not supported" << endl;
   }

   srand(time(0));

   /*
   * RENDERING ALGORITHM NOTES:
   *
   * Basically, I need to split my objects into groups, so that each group fits into
   * GL_MAX_UNIFORM_BLOCK_SIZE. I need to have an offset and a size for each group.
   * Getting the offset is straitforward. The size may as well be GL_MAX_UNIFORM_BLOCK_SIZE
   * for each group, since it seems that smaller sizes just round up to the nearest GL_MAX_UNIFORM_BLOCK_SIZE
   *
   * I'll need to have a loop inside my render loop that calls glBindBufferRange(GL_UNIFORM_BUFFER, ...
   * for every 1024 objects and then draws all those objects with one glDraw call.
   *
   * Since I currently have very few objects, I'll wait to implement this  until I have
   * a reasonable number of objects always using the same shader.
   */

   GLint UNIFORM_BUFFER_OFFSET_ALIGNMENT, MAX_UNIFORM_BLOCK_SIZE;
   glGetIntegerv(GL_UNIFORM_BUFFER_OFFSET_ALIGNMENT, &UNIFORM_BUFFER_OFFSET_ALIGNMENT);
   glGetIntegerv(GL_MAX_UNIFORM_BLOCK_SIZE, &MAX_UNIFORM_BLOCK_SIZE);

   MAX_UNIFORMS = MAX_UNIFORM_BLOCK_SIZE / sizeof(mat4);

   cout << "UNIFORM_BUFFER_OFFSET_ALIGNMENT: " << UNIFORM_BUFFER_OFFSET_ALIGNMENT << endl;
   cout << "MAX_UNIFORMS: " << MAX_UNIFORMS << endl;

   // Setup Dear ImGui binding
   IMGUI_CHECKVERSION();
   ImGui::CreateContext();
   ImGuiIO& io = ImGui::GetIO(); (void)io;
   //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls
   //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;   // Enable Gamepad Controls
   ImGui_ImplGlfwGL3_Init(window, true);

   // Setup style
   ImGui::StyleColorsDark();
   //ImGui::StyleColorsClassic();

   glfwSetMouseButtonCallback(window, mouse_button_callback);
   glfwSetKeyCallback(window, key_callback);

   const GLubyte* renderer = glGetString(GL_RENDERER);
   const GLubyte* version = glGetString(GL_VERSION);
   cout << "Renderer: " << renderer << endl;
   cout << "OpenGL version supported " << version << endl;

   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

   glEnable(GL_DEPTH_TEST);
   glDepthFunc(GL_LESS);

   glEnable(GL_CULL_FACE);
   // glCullFace(GL_BACK);
   // glFrontFace(GL_CW);

   /*
   int x, y;
   unsigned char* texImage = loadImage("test.png", &x, &y);
   if (texImage) {
     cout << "Yay, I loaded an image!" << endl;
     cout << x << endl;
     cout << y << endl;
     printf("first 4 bytes are: %i %i %i %i\n", texImage[0], texImage[1], texImage[2], texImage[3]);
   }

   GLuint testTex = 0;
   glGenTextures(1, &testTex);
   glActiveTexture(GL_TEXTURE0);
   glBindTexture(GL_TEXTURE_2D, testTex);
   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, x, y, 0, GL_RGBA, GL_UNSIGNED_BYTE, texImage);

   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
   glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
   glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   */

   int x, y;
   unsigned char* texImage = loadImage("laser.png", &x, &y);
   if (texImage) {
      cout << "Laser texture loaded successfully!" << endl;
      cout << x << endl;
      cout << y << endl;
      printf("first 4 bytes are: %i %i %i %i\n", texImage[0], texImage[1], texImage[2], texImage[3]);
   }

   GLuint laserTex = 0;
   glGenTextures(1, &laserTex);
   glActiveTexture(GL_TEXTURE0);
   glBindTexture(GL_TEXTURE_2D, laserTex);
   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, x, y, 0, GL_RGBA, GL_UNSIGNED_BYTE, texImage);

   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
   glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
   glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

   /* RENDERING ALGORITHM
    * 
    * Create a separate vbo for each of the following things:
    * - points
    * - colors
    * - texture coordinates
    * - selected colors
    * - normals
    * - indices into a ubo that stores a model matrix for each object
    *
    * Also, make a model matrix ubo, the entirety of which will be passed to the vertex shader.
    * The vbo containing the correct index into the ubo (mentioned above) will be used to select
    * the right model matrix for each point. The index in the vbo will be the saem for all points
    * of any given object.
    *
    * Right now, the currently selected object is drawn using one color (specified in the selected
    * colors vbo) regardless of whether it is normally rendering using colors or a texture. The selected
    * object is rendering by binding the selected colors vbo in place of the colors vbo and using the colors
    * shader. Then, the selected object is redrawn along with all other objects, but the depth buffer test
    * prevents the unselected version of the object from appearing on the screen. This lets me render all the
    * objects that use a particular shader using one glDrawArrays() call.
    */

   GLfloat laserColor[3] = {0.2f, 1.0f, 0.2f};
   GLfloat curTime, prevTime, elapsedTime;

   GLuint ubo = 0;
   glGenBuffers(1, &ubo);

   map<GLuint, BufferInfo> shaderBufferInfo;
   map<ObjectType, ShaderModelGroup> modelGroups;

   modelGroups[TYPE_SHIP] = createModelGroup(
      loadShaderProgram("./ship.vert", "./ship.frag"));
   shaderBufferInfo[modelGroups[TYPE_SHIP].shaderProgram] = BufferInfo(); // temporary

   defineModelGroupAttrib(modelGroups[TYPE_SHIP], "vertex_position", ATTRIB_POINT_VARYING,
      3, GL_FLOAT, offsetof(SceneObject, points));
   defineModelGroupAttrib(modelGroups[TYPE_SHIP], "vertex_color", ATTRIB_POINT_VARYING,
      3, GL_FLOAT, offsetof(SceneObject, colors));
   defineModelGroupAttrib(modelGroups[TYPE_SHIP], "vertex_normal", ATTRIB_POINT_VARYING,
      3, GL_FLOAT, offsetof(SceneObject, normals));
   defineModelGroupAttrib(modelGroups[TYPE_SHIP], "ubo_index", ATTRIB_OBJECT_VARYING,
      1, GL_UNSIGNED_INT, offsetof(SceneObject, ubo_offset));

   defineModelGroupUniform(modelGroups[TYPE_SHIP], "view", ATTRIB_UNIFORM,
      1, UNIFORM_MATRIX_4F, value_ptr(view_mat));
   defineModelGroupUniform(modelGroups[TYPE_SHIP], "proj", ATTRIB_UNIFORM,
      1, UNIFORM_MATRIX_4F, value_ptr(proj_mat));

   initModelGroupAttribs(modelGroups[TYPE_SHIP]);

   modelGroups[TYPE_ASTEROID] = createModelGroup(
      loadShaderProgram("./asteroid.vert", "./asteroid.frag"));
   shaderBufferInfo[modelGroups[TYPE_ASTEROID].shaderProgram] = BufferInfo(); // temporary

   defineModelGroupAttrib(modelGroups[TYPE_ASTEROID], "vertex_position", ATTRIB_POINT_VARYING,
      3, GL_FLOAT, offsetof(SceneObject, points));
   defineModelGroupAttrib(modelGroups[TYPE_ASTEROID], "vertex_color", ATTRIB_POINT_VARYING,
      3, GL_FLOAT, offsetof(SceneObject, colors));
   defineModelGroupAttrib(modelGroups[TYPE_ASTEROID], "vertex_normal", ATTRIB_POINT_VARYING,
      3, GL_FLOAT, offsetof(SceneObject, normals));
   defineModelGroupAttrib(modelGroups[TYPE_ASTEROID], "ubo_index", ATTRIB_OBJECT_VARYING,
      1, GL_UNSIGNED_INT, offsetof(SceneObject, ubo_offset));

   defineModelGroupUniform(modelGroups[TYPE_ASTEROID], "view", ATTRIB_UNIFORM,
      1, UNIFORM_MATRIX_4F, value_ptr(view_mat));
   defineModelGroupUniform(modelGroups[TYPE_ASTEROID], "proj", ATTRIB_UNIFORM,
      1, UNIFORM_MATRIX_4F, value_ptr(proj_mat));

   initModelGroupAttribs(modelGroups[TYPE_ASTEROID]);

   modelGroups[TYPE_LASER] = createModelGroup(
      loadShaderProgram("./laser.vert", "./laser.frag"));
   shaderBufferInfo[modelGroups[TYPE_LASER].shaderProgram] = BufferInfo(); // temporary

   defineModelGroupAttrib(modelGroups[TYPE_LASER], "vertex_position", ATTRIB_POINT_VARYING,
      3, GL_FLOAT, offsetof(SceneObject, points));
   defineModelGroupAttrib(modelGroups[TYPE_LASER], "vt", ATTRIB_POINT_VARYING,
      2, GL_FLOAT, offsetof(SceneObject, texcoords));
   defineModelGroupAttrib(modelGroups[TYPE_LASER], "ubo_index", ATTRIB_OBJECT_VARYING,
      1, GL_UNSIGNED_INT, offsetof(SceneObject, ubo_offset));

   defineModelGroupUniform(modelGroups[TYPE_LASER], "view", ATTRIB_UNIFORM,
      1, UNIFORM_MATRIX_4F, value_ptr(view_mat));
   defineModelGroupUniform(modelGroups[TYPE_LASER], "proj", ATTRIB_UNIFORM,
      1, UNIFORM_MATRIX_4F, value_ptr(proj_mat));
    defineModelGroupUniform(modelGroups[TYPE_LASER], "laser_color", ATTRIB_UNIFORM,
      1, UNIFORM_3F, laserColor);

   initModelGroupAttribs(modelGroups[TYPE_LASER]);

   modelGroups[TYPE_EXPLOSION] = createModelGroup(
      loadShaderProgram("./explosion.vert", "./explosion.frag"));
   shaderBufferInfo[modelGroups[TYPE_EXPLOSION].shaderProgram] = BufferInfo(); // temporary

   // The last parameter (offset) is only used for populating the buffers since the distance
   // between each item is needed there. However, the explosion vbos are populated using different
   // code anyway and don't use that argument, so I may as well pass in 0 here.
   defineModelGroupAttrib(modelGroups[TYPE_EXPLOSION], "v_i", ATTRIB_POINT_VARYING,
      3, GL_FLOAT, 0);
   defineModelGroupAttrib(modelGroups[TYPE_EXPLOSION], "start_time", ATTRIB_POINT_VARYING,
      1, GL_FLOAT, 0);
   defineModelGroupAttrib(modelGroups[TYPE_EXPLOSION], "ubo_index", ATTRIB_OBJECT_VARYING,
      1, GL_UNSIGNED_INT, offsetof(SceneObject, ubo_offset));

   defineModelGroupUniform(modelGroups[TYPE_EXPLOSION], "explosion_start_time", ATTRIB_UNIFORM,
      1, UNIFORM_1F, &curTime);
   defineModelGroupUniform(modelGroups[TYPE_EXPLOSION], "cur_time", ATTRIB_UNIFORM,
      1, UNIFORM_1F, &curTime);
   defineModelGroupUniform(modelGroups[TYPE_EXPLOSION], "view", ATTRIB_UNIFORM,
      1, UNIFORM_MATRIX_4F, value_ptr(view_mat));
   defineModelGroupUniform(modelGroups[TYPE_EXPLOSION], "proj", ATTRIB_UNIFORM,
      1, UNIFORM_MATRIX_4F, value_ptr(proj_mat));

   initModelGroupAttribs(modelGroups[TYPE_EXPLOSION]);

   cam_pos = vec3(0.0f, 0.0f, 2.0f);
   float cam_yaw = 0.0f * 2.0f * 3.14159f / 360.0f;
   float cam_pitch = -50.0f * 2.0f * 3.14159f / 360.0f;

   // player ship
   objects.push_back(createShip());

   vector<SceneObject>::iterator obj_it;

   populateBuffers(objects,
      shaderBufferInfo, modelGroups,
      ubo);

   float cam_speed = 1.0f;
   float cam_yaw_speed = 60.0f*ONE_DEG_IN_RAD;
   float cam_pitch_speed = 60.0f*ONE_DEG_IN_RAD;

   // glm::lookAt can create the view matrix
   // glm::perspective can create the projection matrix

   mat4 T = translate(mat4(1.0f), vec3(-cam_pos.x, -cam_pos.y, -cam_pos.z));
   mat4 yaw_mat = rotate(mat4(1.0f), -cam_yaw, vec3(0.0f, 1.0f, 0.0f));
   mat4 pitch_mat = rotate(mat4(1.0f), -cam_pitch, vec3(1.0f, 0.0f, 0.0f));
   mat4 R = pitch_mat * yaw_mat;
   view_mat = R*T;

   // TODO: Create a function to construct the projection matrix
   // (Maybe I should just use glm::perspective, after making sure it matches what I have now)
   float fov = 67.0f * ONE_DEG_IN_RAD;
   float aspect = (float)width / (float)height;

   float range = tan(fov * 0.5f) * NEAR_CLIP;
   float Sx = NEAR_CLIP / (range * aspect);
   float Sy = NEAR_CLIP / range;
   float Sz = -(FAR_CLIP + NEAR_CLIP) / (FAR_CLIP - NEAR_CLIP);
   float Pz = -(2.0f * FAR_CLIP * NEAR_CLIP) / (FAR_CLIP - NEAR_CLIP);

   float proj_arr[] = {
     Sx, 0.0f, 0.0f, 0.0f,
     0.0f, Sy, 0.0f, 0.0f,
     0.0f, 0.0f, Sz, -1.0f,
     0.0f, 0.0f, Pz, 0.0f,
   };
   proj_mat = make_mat4(proj_arr);

   initializeParticleEffectBuffers(shaderBufferInfo, modelGroups, ubo);

   /* TODO: Fix the UBO binding code based on the following forum post (in order to support multiple ubos):

      No, you're misunderstanding how this works. UBO binding works exactly like texture object binding.

      The OpenGL context has a number of slots for binding UBOs. There are GL_MAX_UNIFORM_BUFFER_BINDINGS number of
      slots for UBO binding.

      Uniform Blocks in a program can be set to use one of the slots in the context. You do this by first querying
      the block index using the block name (glGetUniformBlockIndex). This is similar to how you need to use
      glGetUniformLocation in order to set a uniform's value with glUniform. Block indices, like uniform locations,
      are specific to a program.

      Once you have the block index, you use glUniformBlockBinding to set that specific program to use a particular
      uniform buffer slot in the context.

      Let's say you have a global UBO that you want to use for every program. To make using it easier, you want to
      bind it just once.

      So first, you pick a uniform buffer slot in the context, one that always will refer to this UBO. Let's say
      you pick slot 8.

      When you build a program object that may use this global uniform buffer, what you do is quite simple. First,
      after linking the program, call glGetUniformBlockIndex(program, "NameOfGlobalUniformBlock"). If you get back
      GL_INVALID_INDEX, then you know that the global uniform block isn't used in that program. Otherwise you get
      back a block index.

      If you got a valid block index, then you call glUniformBlockBinding(program, uniformBlockIndex, 8). Remember
      that 8 is the uniform buffer context slot that we selected earlier. This causes this particular program to
      use uniform buffer slot #8 to find the buffer for "NameOfGlobalUniformBlock".

      Finally, to set the actual buffer in the context, call glBindBufferRange(GL_UNIFORM_BUFFER, 8,
      bufferObjectName, offset, size);
   */

   GLuint ub_binding_point = 0;

   GLuint ship_sp_models_ub_index = glGetUniformBlockIndex(modelGroups[TYPE_SHIP].shaderProgram, "models");

   GLuint asteroid_sp_models_ub_index = glGetUniformBlockIndex(modelGroups[TYPE_ASTEROID].shaderProgram, "models");

   GLuint laser_sp_models_ub_index = glGetUniformBlockIndex(modelGroups[TYPE_LASER].shaderProgram, "models");

   GLuint explosion_sp_models_ub_index = glGetUniformBlockIndex(modelGroups[TYPE_EXPLOSION].shaderProgram, "models");


   glUseProgram(modelGroups[TYPE_SHIP].shaderProgram);
   bindUniformData(modelGroups[TYPE_SHIP].attribs["view"]);
   bindUniformData(modelGroups[TYPE_SHIP].attribs["proj"]);

   glUniformBlockBinding(modelGroups[TYPE_SHIP].shaderProgram, ship_sp_models_ub_index, ub_binding_point);
   glBindBufferRange(GL_UNIFORM_BUFFER, ub_binding_point, ubo, 0, GL_MAX_UNIFORM_BLOCK_SIZE);


   glUseProgram(modelGroups[TYPE_ASTEROID].shaderProgram);
   bindUniformData(modelGroups[TYPE_ASTEROID].attribs["view"]);
   bindUniformData(modelGroups[TYPE_ASTEROID].attribs["proj"]);

   glUniformBlockBinding(modelGroups[TYPE_ASTEROID].shaderProgram, asteroid_sp_models_ub_index, ub_binding_point);
   glBindBufferRange(GL_UNIFORM_BUFFER, ub_binding_point, ubo, 0, GL_MAX_UNIFORM_BLOCK_SIZE);


   // may want to do initialization for basic_texture uniform here too
   // Right now, I think I'm getting away without getting that uniform location because I'm only
   // using one texture, so setting it to GL_TEXTURE0 once works
   glUseProgram(modelGroups[TYPE_LASER].shaderProgram);
   bindUniformData(modelGroups[TYPE_LASER].attribs["view"]);
   bindUniformData(modelGroups[TYPE_LASER].attribs["proj"]);
   bindUniformData(modelGroups[TYPE_LASER].attribs["laser_color"]);

   glUniformBlockBinding(modelGroups[TYPE_LASER].shaderProgram, laser_sp_models_ub_index, ub_binding_point);
   glBindBufferRange(GL_UNIFORM_BUFFER, ub_binding_point, ubo, 0, GL_MAX_UNIFORM_BLOCK_SIZE);


   glUseProgram(modelGroups[TYPE_EXPLOSION].shaderProgram);
   glUniformBlockBinding(modelGroups[TYPE_EXPLOSION].shaderProgram, explosion_sp_models_ub_index, ub_binding_point);
   glBindBufferRange(GL_UNIFORM_BUFFER, ub_binding_point, ubo, 0, GL_MAX_UNIFORM_BLOCK_SIZE);


   double fps;
   unsigned int score = 0;

   bool cam_moved = false;

   int frame_count = 0;
   double elapsed_seconds_fps = 0.0f;
   double elapsed_seconds_spawn = 0.0f;

   prevTime = glfwGetTime();

   // This draws wireframes. Useful for seeing separate faces and occluded objects.
   //glPolygonMode(GL_FRONT, GL_LINE);

   // disable vsync to see real framerate
   //glfwSwapInterval(0);

   State curState = STATE_MAIN_MENU;

   initGuiValueLists(valueLists);

   valueLists["stats value list"].push_back(UIValue(UIVALUE_INT, "Score", &score));
   valueLists["stats value list"].push_back(UIValue(UIVALUE_DOUBLE, "FPS", &fps));

   while (!glfwWindowShouldClose(window) && isRunning) {
      curTime = glfwGetTime();
      elapsedTime = curTime - prevTime;

      // temporary code to get around vsync issue in OSX Sierra
      if (elapsedTime < (1.0f / TARGET_FPS)) {
        continue;
      }

      prevTime = curTime;

      elapsed_seconds_fps += elapsedTime;
      if (elapsed_seconds_fps > 0.25f) {
         fps = (double)frame_count / elapsed_seconds_fps;

         frame_count = 0;
         elapsed_seconds_fps = 0.0f;
      }

      frame_count++;

      // Handle events

      clickedObject = NULL;

      // reset the all key states to KEY_STATE_UNCHANGED (something the GLFW key callback can never return)
      // so that GLFW_PRESS and GLFW_RELEASE are only detected once
      // TODO: Change this if we ever need to act on GLFW_REPEAT (which is when a key is held down
      //  continuously for a period of time)
      fill(key_state, key_state + NUM_KEYS, KEY_STATE_UNCHANGED);

      glfwPollEvents();

      while (!events.empty()) {
         switch (events.front()) {
            case EVENT_GO_TO_MAIN_MENU:
               curState = STATE_MAIN_MENU;
               break;
            case EVENT_GO_TO_GAME:
               curState = STATE_GAME;
               break;
            case EVENT_QUIT:
               isRunning = false;
               break;
         }
         events.pop();
      }

      if (curState == STATE_GAME) {

         elapsed_seconds_spawn += elapsedTime;
         if (elapsed_seconds_spawn > 0.5f) {
            SceneObject* obj = createAsteroid(vec3(getRandomNum(-1.3f, 1.3f), -1.2f, getRandomNum(-5.5f, -4.5f)));
            addObjectToScene(obj, shaderBufferInfo, modelGroups, ubo);

            elapsed_seconds_spawn -= 0.5f;
         }

         /*
         if (clickedObject == &objects[0]) {
            selectedObject = &objects[0];
         }
         if (clickedObject == &objects[1]) {
            selectedObject = &objects[1];
         }
         */

         /*
         if (key_state[GLFW_KEY_SPACE] == GLFW_PRESS) {
            transformObject(objects[1], translate(mat4(1.0f), vec3(0.3f, 0.0f, 0.0f)), ubo);
         }
         if (key_down[GLFW_KEY_RIGHT]) {
            transformObject(objects[2], translate(mat4(1.0f), vec3(0.01f, 0.0f, 0.0f)), ubo);
         }
         if (key_down[GLFW_KEY_LEFT]) {
            transformObject(objects[2], translate(mat4(1.0f), vec3(-0.01f, 0.0f, 0.0f)), ubo);
         }
         */

         if (key_down[GLFW_KEY_RIGHT]) {
            transformObject(*objects[0], translate(mat4(1.0f), vec3(0.01f, 0.0f, 0.0f)), ubo);

            if (leftLaser != NULL && !leftLaser->deleted) {
               translateLaser(leftLaser, vec3(0.01f, 0.0f, 0.0f), ubo);
            }
            if (rightLaser != NULL && !rightLaser->deleted) {
               translateLaser(rightLaser, vec3(0.01f, 0.0f, 0.0f), ubo);
            }
         }
         if (key_down[GLFW_KEY_LEFT]) {
            transformObject(*objects[0], translate(mat4(1.0f), vec3(-0.01f, 0.0f, 0.0f)), ubo);

            if (leftLaser != NULL && !leftLaser->deleted) {
               translateLaser(leftLaser, vec3(-0.01f, 0.0f, 0.0f), ubo);
            }
            if (rightLaser != NULL && !rightLaser->deleted) {
               translateLaser(rightLaser, vec3(-0.01f, 0.0f, 0.0f), ubo);
            }
         }

         if (key_state[GLFW_KEY_Z] == GLFW_PRESS) {
            vec3 offset(objects[0]->model_transform * vec4(0.0f, 0.0f, 0.0f, 1.0f));

            leftLaser = createLaser(
               vec3(-0.21f, -1.19f, 1.76f)+offset,
               vec3(-0.21f, -1.19f, -3.0f)+offset,
               vec3(0.0f, 1.0f, 0.0f), 0.03f);
            addObjectToScene(leftLaser, shaderBufferInfo, modelGroups, ubo);
         } else if (key_state[GLFW_KEY_Z] == GLFW_RELEASE) {
            removeObjectFromScene(*leftLaser, ubo);
         }

         if (key_state[GLFW_KEY_X] == GLFW_PRESS) {
            vec3 offset(objects[0]->model_transform * vec4(0.0f, 0.0f, 0.0f, 1.0f));

            rightLaser = createLaser(
               vec3(0.21f, -1.19f, 1.76f) + offset,
               vec3(0.21f, -1.19f, -3.0f) + offset,
               vec3(0.0f, 1.0f, 0.0f), 0.03f);
            addObjectToScene(rightLaser, shaderBufferInfo, modelGroups, ubo);
         } else if (key_state[GLFW_KEY_X] == GLFW_RELEASE) {
            removeObjectFromScene(*rightLaser, ubo);
         }

         // this code moves the asteroids
         for (unsigned int i = 0; i < objects.size(); i++) {
            if (objects[i]->type == TYPE_ASTEROID && !objects[i]->deleted) {
               transformObject(*objects[i], translate(mat4(1.0f), vec3(0.0f, 0.0f, 0.04f)), ubo);

               vec3 obj_center = vec3(view_mat * vec4(objects[i]->bounding_center, 1.0f));

               if ((obj_center.z - objects[i]->bounding_radius) > -NEAR_CLIP) {
                  removeObjectFromScene(*objects[i], ubo);
               }
               if (((Asteroid*)objects[i])->hp <= 0) {
                  // TODO: Optimize this so I don't recalculate the camera rotation every time
                  float cam_pitch = -50.0f * 2.0f * 3.14159f / 360.0f;
                  mat4 pitch_mat = rotate(mat4(1.0f), cam_pitch, vec3(1.0f, 0.0f, 0.0f));
                  mat4 model_mat = translate(mat4(1.0f), objects[i]->bounding_center + vec3(0.0f, 0.0f, 0.0f)) * pitch_mat;

                  removeObjectFromScene(*objects[i], ubo);
                  score++;

                  objExplosion->model_mat = model_mat;

                  // initiate an explosion
                  glUseProgram(modelGroups[TYPE_EXPLOSION].shaderProgram);

                  bindUniformData(modelGroups[TYPE_EXPLOSION].attribs["explosion_start_time"]);

                  glBindBuffer(GL_UNIFORM_BUFFER, ubo);
                  glBufferSubData(GL_UNIFORM_BUFFER, objExplosion->ubo_offset * sizeof(mat4), sizeof(mat4), value_ptr(objExplosion->model_mat));
               }
            }
         }

         if (leftLaser != NULL && !leftLaser->deleted) {
            updateLaserTarget(leftLaser, objects, modelGroups[TYPE_LASER], modelGroups[TYPE_ASTEROID].shaderProgram);
         }
         if (rightLaser != NULL && !rightLaser->deleted) {
            updateLaserTarget(rightLaser, objects, modelGroups[TYPE_LASER], modelGroups[TYPE_ASTEROID].shaderProgram);
         }
      }

      for (vector<EffectOverTime*>::iterator it = effects.begin(); it != effects.end(); ) {
         if ((*it)->deleted || (*it)->effectedObject->deleted) {
            delete *it;
            it = effects.erase(it);
         } else {
            EffectOverTime* eot = *it;
            eot->effectedValue = eot->startValue + (curTime - eot->startTime) * eot->changePerSecond;

            it++;
         }
      }

      if (key_state[GLFW_KEY_ESCAPE] == GLFW_PRESS) {
         glfwSetWindowShouldClose(window, 1);
      }

      float dist = cam_speed * elapsedTime;
      if (key_down[GLFW_KEY_A]) {
         vec3 dir = vec3(inverse(R) * vec4(-1.0f, 0.0f, 0.0f, 1.0f));
         cam_pos += dir * dist;

         cam_moved = true;
      }
      if (key_down[GLFW_KEY_D]) {
         vec3 dir = vec3(inverse(R) * vec4(1.0f, 0.0f, 0.0f, 1.0f));
         cam_pos += dir * dist;

         cam_moved = true;
      }
      if (key_down[GLFW_KEY_W]) {
         vec3 dir = vec3(inverse(R) * vec4(0.0f, 0.0f, -1.0f, 1.0f));
         cam_pos += dir * dist;

         cam_moved = true;
      }
      if (key_down[GLFW_KEY_S]) {
         vec3 dir = vec3(inverse(R) * vec4(0.0f, 0.0f, 1.0f, 1.0f));
         cam_pos += dir * dist;

         cam_moved = true;
      }
      /*
      if (key_down[GLFW_KEY_LEFT]) {
      cam_yaw += cam_yaw_speed * elapsedTime;
      cam_moved = true;
      }
      if (key_down[GLFW_KEY_RIGHT]) {
      cam_yaw -= cam_yaw_speed * elapsedTime;
      cam_moved = true;
      }
      if (key_down[GLFW_KEY_UP]) {
      cam_pitch += cam_pitch_speed * elapsedTime;
      cam_moved = true;
      }
      if (key_down[GLFW_KEY_DOWN]) {
      cam_pitch -= cam_pitch_speed * elapsedTime;
      cam_moved = true;
      }
      */
      if (cam_moved && false) { // disable camera movement
         T = translate(mat4(1.0f), vec3(-cam_pos.x, -cam_pos.y, -cam_pos.z));

         mat4 yaw_mat = rotate(mat4(1.0f), -cam_yaw, vec3(0.0f, 1.0f, 0.0f));
         mat4 pitch_mat = rotate(mat4(1.0f), -cam_pitch, vec3(1.0f, 0.0f, 0.0f));
         R = pitch_mat * yaw_mat;

         view_mat = R * T;

         glUseProgram(modelGroups[TYPE_SHIP].shaderProgram);
         bindUniformData(modelGroups[TYPE_SHIP].attribs["view"]);

         glUseProgram(modelGroups[TYPE_LASER].shaderProgram);
         bindUniformData(modelGroups[TYPE_LASER].attribs["view"]);

         cam_moved = false;
      }

      glUseProgram(modelGroups[TYPE_EXPLOSION].shaderProgram);
      bindUniformData(modelGroups[TYPE_EXPLOSION].attribs["cur_time"]);

      // Render scene

      glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

      switch (curState) {
         case STATE_MAIN_MENU:
            renderMainMenu();
            renderMainMenuGui();
            break;
         case STATE_GAME:
            renderScene(shaderBufferInfo, modelGroups, ubo);
            renderSceneGui(valueLists);
            break;
      }

      glfwSwapBuffers(window);
   }

   ImGui_ImplGlfwGL3_Shutdown();
   ImGui::DestroyContext();

   glfwDestroyWindow(window);
   glfwTerminate();

   // free memory

   for (vector<SceneObject*>::iterator it = objects.begin(); it != objects.end(); it++) {
      delete *it;
   }

   return 0;
}

void glfw_error_callback(int error, const char* description) {
   gl_log_err("GLFW ERROR: code %i msg: %s\n", error, description);
}

void mouse_button_callback(GLFWwindow* window, int button, int action, int mods) {
   double mouse_x, mouse_y;
   glfwGetCursorPos(window, &mouse_x, &mouse_y);

   if (button == GLFW_MOUSE_BUTTON_LEFT && action == GLFW_PRESS) {
      cout << "Mouse clicked (" << mouse_x << "," << mouse_y << ")" << endl;
      selectedObject = NULL;

      float x = (2.0f*mouse_x) / width - 1.0f;
      float y = 1.0f - (2.0f*mouse_y) / height;

      cout << "x: " << x << ", y: " << y << endl;

      vec4 ray_clip = vec4(x, y, -1.0f, 1.0f);
      vec4 ray_eye = inverse(proj_mat) * ray_clip;
      ray_eye = vec4(vec2(ray_eye), -1.0f, 1.0f);
      vec4 ray_world = inverse(view_mat) * ray_eye;

      vec4 click_point;
      vec3 closest_point = vec3(0.0f, 0.0f, -FAR_CLIP); // Any valid point will be closer than the far clipping plane, so initial value to that
      SceneObject* closest_object = NULL;

      for (vector<SceneObject*>::iterator it = objects.begin(); it != objects.end(); it++) {
         if ((*it)->type == TYPE_LASER) continue;
         for (unsigned int p_idx = 0; p_idx < (*it)->points.size(); p_idx += 9) {
            if (faceClicked(
               {
                  vec3((*it)->points[p_idx], (*it)->points[p_idx + 1], (*it)->points[p_idx + 2]),
                  vec3((*it)->points[p_idx + 3], (*it)->points[p_idx + 4], (*it)->points[p_idx + 5]),
                  vec3((*it)->points[p_idx + 6], (*it)->points[p_idx + 7], (*it)->points[p_idx + 8]),
               },
               *it, ray_world, vec4(cam_pos, 1.0f), click_point
            )) {
               click_point = view_mat * click_point;

               if (-NEAR_CLIP >= click_point.z && click_point.z > -FAR_CLIP && click_point.z > closest_point.z) {
                  closest_point = vec3(click_point);
                  closest_object = *it;
               }
            }
         }
      }

      if (closest_object == NULL) {
         cout << "No object was clicked" << endl;
      } else {
         clickedObject = closest_object;
         cout << "Clicked object: " << clickedObject->id << endl;
      }
   }
}

void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods) {
   key_state[key] = action;

   // should be true for GLFW_PRESS and GLFW_REPEAT
   key_down[key] = (action != GLFW_RELEASE);
}

void APIENTRY debugGlCallback(
   GLenum source,
   GLenum type,
   GLuint id,
   GLenum severity,
   GLsizei length,
   const GLchar* message,
   const void* userParam
) {
   string strMessage(message);

   // TODO: Use C++ strings directly
   char source_str[2048];
   char type_str[2048];
   char severity_str[2048];

   switch (source) {
      case 0x8246:
         strcpy(source_str, "API");
         break;
      case 0x8247:
         strcpy(source_str, "WINDOW_SYSTEM");
         break;
      case 0x8248:
         strcpy(source_str, "SHADER_COMPILER");
         break;
      case 0x8249:
         strcpy(source_str, "THIRD_PARTY");
         break;
      case 0x824A:
         strcpy(source_str, "APPLICATION");
         break;
      case 0x824B:
         strcpy(source_str, "OTHER");
         break;
      default:
         strcpy(source_str, "undefined");
         break;
   }

   switch (type) {
      case 0x824C:
         strcpy(type_str, "ERROR");
         break;
      case 0x824D:
         strcpy(type_str, "DEPRECATED_BEHAVIOR");
         break;
      case 0x824E:
         strcpy(type_str, "UNDEFINED_BEHAVIOR");
         break;
      case 0x824F:
         strcpy(type_str, "PORTABILITY");
         break;
      case 0x8250:
         strcpy(type_str, "PERFORMANCE");
         break;
      case 0x8251:
         strcpy(type_str, "OTHER");
         break;
      case 0x8268:
         strcpy(type_str, "MARKER");
         break;
      case 0x8269:
         strcpy(type_str, "PUSH_GROUP");
         break;
      case 0x826A:
         strcpy(type_str, "POP_GROUP");
         break;
      default:
         strcpy(type_str, "undefined");
         break;
   }
   switch (severity) {
      case 0x9146:
         strcpy(severity_str, "HIGH");
         break;
      case 0x9147:
         strcpy(severity_str, "MEDIUM");
         break;
      case 0x9148:
         strcpy(severity_str, "LOW");
         break;
      case 0x826B:
         strcpy(severity_str, "NOTIFICATION");
         break;
      default:
         strcpy(severity_str, "undefined");
         break;
   }

   if (string(severity_str) != "NOTIFICATION") {
      cout << "OpenGL Error!!!" << endl;
      cout << "Source: " << string(source_str) << endl;
      cout << "Type: " << string(type_str) << endl;
      cout << "Severity: " << string(severity_str) << endl;
      cout << strMessage << endl;
   }
}


GLuint loadShader(GLenum type, string file) {
  cout << "Loading shader from file " << file << endl;

  ifstream shaderFile(file);
  GLuint shaderId = 0;

  if (shaderFile.is_open()) {
    string line, shaderString;

    while(getline(shaderFile, line)) {
      shaderString += line + "\n";
    }
    shaderFile.close();
    const char* shaderCString = shaderString.c_str();

    shaderId = glCreateShader(type);
    glShaderSource(shaderId, 1, &shaderCString, NULL);
    glCompileShader(shaderId);

    cout << "Loaded successfully" << endl;
  } else {
    cout << "Failed to load the file" << endl;
  }

  return shaderId;
}

GLuint loadShaderProgram(string vertexShaderPath, string fragmentShaderPath) {
   GLuint vs = loadShader(GL_VERTEX_SHADER, vertexShaderPath);
   GLuint fs = loadShader(GL_FRAGMENT_SHADER, fragmentShaderPath);

   GLuint shader_program = glCreateProgram();
   glAttachShader(shader_program, vs);
   glAttachShader(shader_program, fs);

   glLinkProgram(shader_program);

   return shader_program;
}

unsigned char* loadImage(string file_name, int* x, int* y) {
  int n;
  int force_channels = 4; // This forces RGBA (4 bytes per pixel)
  unsigned char* image_data = stbi_load(file_name.c_str(), x, y, &n, force_channels);

  int width_in_bytes = *x * 4;
  unsigned char *top = NULL;
  unsigned char *bottom = NULL;
  unsigned char temp = 0;
  int half_height = *y / 2;

  // flip image upside-down to account for OpenGL treating lower-left as (0, 0)
  for (int row = 0; row < half_height; row++) {
     top = image_data + row * width_in_bytes;
     bottom = image_data + (*y - row - 1) * width_in_bytes;
     for (int col = 0; col < width_in_bytes; col++) {
        temp = *top;
        *top = *bottom;
        *bottom = temp;
        top++;
        bottom++;
     }
  }

  if (!image_data) {
    fprintf(stderr, "ERROR: could not load %s\n", file_name.c_str());
  }

  // Not Power-of-2 check
  if ((*x & (*x - 1)) != 0 || (*y & (*y - 1)) != 0) {
     fprintf(stderr, "WARNING: texture %s is not power-of-2 dimensions\n", file_name.c_str());
  }

  return image_data;
}

bool faceClicked(array<vec3, 3> points, SceneObject* obj, vec4 world_ray, vec4 cam, vec4& click_point) {
   // LINE EQUATION:            P = O + Dt
   // O = cam
   // D = ray_world

   // PLANE EQUATION:   P dot n + d = 0
   // n is the normal vector
   // d is the offset from the origin

   // Take the cross-product of two vectors on the plane to get the normal
   vec3 v1 = points[1] - points[0];
   vec3 v2 = points[2] - points[0];

   vec3 normal = vec3(v1.y*v2.z - v1.z*v2.y, v1.z*v2.x - v1.x*v2.z, v1.x*v2.y - v1.y*v2.x);

   vec3 local_ray = vec3(inverse(obj->model_mat) * world_ray);
   vec3 local_cam = vec3(inverse(obj->model_mat) * cam);

   local_ray = local_ray - local_cam;

   float d = -glm::dot(points[0], normal);
   float t = -(glm::dot(local_cam, normal) + d) / glm::dot(local_ray, normal);

   vec3 intersection = local_cam + t*local_ray;

   if (insideTriangle(intersection, points)) {
      click_point = obj->model_mat * vec4(intersection, 1.0f);
      return true;
   } else {
      return false;
   }
}

bool insideTriangle(vec3 p, array<vec3, 3> triangle_points) {
   vec3 v21 = triangle_points[1] - triangle_points[0];
   vec3 v31 = triangle_points[2] - triangle_points[0];
   vec3 pv1 = p - triangle_points[0];

   float y = (pv1.y*v21.x - pv1.x*v21.y) / (v31.y*v21.x - v31.x*v21.y);
   float x = (pv1.x-y*v31.x) / v21.x;

   return x > 0.0f && y > 0.0f && x+y < 1.0f;
}

void printVector(string label, vec3& v) {
   cout << label << " -> (" << v.x << "," << v.y << "," << v.z << ")" << endl;
}

void print4DVector(string label, vec4& v) {
   cout << label << " -> (" << v.x << "," << v.y << "," << v.z << "," << v.w << ")" << endl;
}

void initObject(SceneObject* obj) {
   // Each objects must have at least 3 points, so the size of
   // the points array must be a positive multiple of 9
   if (obj->points.size() == 0 || (obj->points.size() % 9) != 0) {
      // TODO: Maybe throw some kind of error here instead
      return;
   }

   obj->id = objects.size(); // currently unused
   obj->num_points = obj->points.size() / 3;
   obj->model_transform = mat4(1.0f);
   obj->deleted = false;

   obj->normals.reserve(obj->points.size());
   for (unsigned int i = 0; i < obj->points.size(); i += 9) {
      vec3 point1 = vec3(obj->points[i], obj->points[i + 1], obj->points[i + 2]);
      vec3 point2 = vec3(obj->points[i + 3], obj->points[i + 4], obj->points[i + 5]);
      vec3 point3 = vec3(obj->points[i + 6], obj->points[i + 7], obj->points[i + 8]);

      vec3 normal = normalize(cross(point2 - point1, point3 - point1));

      // Add the same normal for all 3 points
      for (int j = 0; j < 3; j++) {
         obj->normals.push_back(normal.x);
         obj->normals.push_back(normal.y);
         obj->normals.push_back(normal.z);
      }
   }

   if (obj->type == TYPE_SHIP || obj->type == TYPE_ASTEROID) {
      calculateObjectBoundingBox(obj);

      obj->bounding_center = vec3(obj->translate_mat * vec4(obj->bounding_center, 1.0f));
   }
}

void addObjectToScene(SceneObject* obj,
   map<GLuint, BufferInfo>& shaderBufferInfo,
   map<ObjectType, ShaderModelGroup>& modelGroups,
   GLuint ubo) {
   objects.push_back(obj);

   BufferInfo* bufferInfo = &shaderBufferInfo[modelGroups[obj->type].shaderProgram];

   // Check if the buffers aren't large enough to fit the new object and, if so, call
   // populateBuffers() to resize and repopupulate them
   if (modelGroups[obj->type].vboCapacity < (modelGroups[obj->type].numPoints + obj->num_points) ||
      bufferInfo->ubo_capacity < (bufferInfo->ubo_offset + 1)) {

      if (leftLaser != NULL && leftLaser->deleted) {
         leftLaser = NULL;
      }
      if (rightLaser != NULL && rightLaser->deleted) {
         rightLaser = NULL;
      }

      populateBuffers(objects, shaderBufferInfo, modelGroups, ubo);
   } else {
      copyObjectDataToBuffers(*objects.back(), shaderBufferInfo, modelGroups, ubo);
   }
}

void removeObjectFromScene(SceneObject& obj, GLuint ubo) {
   if (!obj.deleted) {
      // Move the object outside the render bounds of the scene so it doesn't get rendered
      // TODO: Find a better way of hiding the object until the next time buffers are repopulated
      transformObject(obj, translate(mat4(1.0f), vec3(0.0f, 0.0f, FAR_CLIP * 1000.0f)), ubo);
      obj.deleted = true;
   }
}

void calculateObjectBoundingBox(SceneObject* obj) {
   GLfloat min_x = obj->points[0];
   GLfloat max_x = obj->points[0];
   GLfloat min_y = obj->points[1];
   GLfloat max_y = obj->points[1];
   GLfloat min_z = obj->points[2];
   GLfloat max_z = obj->points[2];

   // start from the second point
   for (unsigned int i = 3; i < obj->points.size(); i += 3) {
      if (min_x > obj->points[i]) {
         min_x = obj->points[i];
      }
      else if (max_x < obj->points[i]) {
         max_x = obj->points[i];
      }

      if (min_y > obj->points[i + 1]) {
         min_y = obj->points[i + 1];
      }
      else if (max_y < obj->points[i + 1]) {
         max_y = obj->points[i + 1];
      }

      if (min_z > obj->points[i + 2]) {
         min_z = obj->points[i + 2];
      }
      else if (max_z < obj->points[i + 2]) {
         max_z = obj->points[i + 2];
      }
   }

   obj->bounding_center = vec3((min_x + max_x) / 2.0f, (min_y + max_y) / 2.0f, (min_z + max_z) / 2.0f);

   GLfloat radius_x = max_x - obj->bounding_center.x;
   GLfloat radius_y = max_y - obj->bounding_center.y;
   GLfloat radius_z = max_z - obj->bounding_center.z;

   // TODO: This actually underestimates the radius. Might need to be fixed at some point.
   // TODO: Does not take into account any scaling in the model matrix
   obj->bounding_radius = radius_x;
   if (obj->bounding_radius < radius_y)
      obj->bounding_radius = radius_y;
   if (obj->bounding_radius < radius_z)
      obj->bounding_radius = radius_z;

   for (unsigned int i = 0; i < obj->points.size(); i += 3) {
      obj->points[i] -= obj->bounding_center.x;
      obj->points[i + 1] -= obj->bounding_center.y;
      obj->points[i + 2] -= obj->bounding_center.z;
   }

   obj->bounding_center = vec3(0.0f, 0.0f, 0.0f);
}

SceneObject* createShip() {
   SceneObject* ship = new SceneObject();

   ship->type = TYPE_SHIP;

   ship->points = {
      //back
      -0.5f,    0.3f,    0.0f,
      -0.5f,    0.0f,    0.0f,
      0.5f,    0.0f,    0.0f,
      -0.5f,    0.3f,    0.0f,
      0.5f,    0.0f,    0.0f,
      0.5f,    0.3f,    0.0f,

      // left back
      -0.5f,    0.3f,   -2.0f,
      -0.5f,    0.0f,   -2.0f,
      -0.5f,    0.0f,    0.0f,
      -0.5f,    0.3f,   -2.0f,
      -0.5f,    0.0f,    0.0f,
      -0.5f,    0.3f,    0.0f,

      // right back
      0.5f,    0.3f,    0.0f,
      0.5f,    0.0f,    0.0f,
      0.5f,    0.0f,   -2.0f,
      0.5f,    0.3f,    0.0f,
      0.5f,    0.0f,   -2.0f,
      0.5f,    0.3f,   -2.0f,

      // left mid
      -0.25f,   0.3f,   -3.0f,
      -0.25f,   0.0f,   -3.0f,
      -0.5f,    0.0f,   -2.0f,
      -0.25f,   0.3f,   -3.0f,
      -0.5f,    0.0f,   -2.0f,
      -0.5f,    0.3f,   -2.0f,

      // right mid
      0.5f,    0.3f,   -2.0f,
      0.5f,    0.0f,   -2.0f,
      0.25f,   0.0f,   -3.0f,
      0.5f,    0.3f,   -2.0f,
      0.25f,   0.0f,   -3.0f,
      0.25f,   0.3f,   -3.0f,

      // left front
      0.0f,    0.0f,   -3.5f,
      -0.25f,   0.0f,   -3.0f,
      -0.25f,   0.3f,   -3.0f,

      // right front
      0.25f,   0.3f,   -3.0f,
      0.25f,   0.0f,   -3.0f,
      0.0f,    0.0f,   -3.5f,

      // top back
      -0.5f,    0.3f,   -2.0f,
      -0.5f,    0.3f,    0.0f,
      0.5f,    0.3f,    0.0f,
      -0.5f,    0.3f,   -2.0f,
      0.5f,    0.3f,    0.0f,
      0.5f,    0.3f,   -2.0f,

      // bottom back
      -0.5f,    0.0f,    0.0f,
      -0.5f,    0.0f,   -2.0f,
      0.5f,    0.0f,    0.0f,
      0.5f,    0.0f,    0.0f,
      -0.5f,    0.0f,   -2.0f,
      0.5f,    0.0f,   -2.0f,

      // top mid
      -0.25f,   0.3f,   -3.0f,
      -0.5f,    0.3f,   -2.0f,
      0.5f,    0.3f,   -2.0f,
      -0.25f,   0.3f,   -3.0f,
      0.5f,    0.3f,   -2.0f,
      0.25f,   0.3f,   -3.0f,

      // bottom mid
      -0.5f,    0.0f,   -2.0f,
      -0.25f,   0.0f,   -3.0f,
      0.5f,    0.0f,   -2.0f,
      0.5f,    0.0f,   -2.0f,
      -0.25f,   0.0f,   -3.0f,
      0.25f,   0.0f,   -3.0f,

      // top front
      -0.25f,   0.3f,   -3.0f,
      0.25f,   0.3f,   -3.0f,
      0.0f,    0.0f,   -3.5f,

      // bottom front
      0.25f,   0.0f,   -3.0f,
      -0.25f,   0.0f,   -3.0f,
      0.0f,    0.0f,   -3.5f,

      // left wing start back
      -1.5f,    0.3f,    0.0f,
      -1.5f,    0.0f,    0.0f,
      -0.5f,    0.0f,    0.0f,
      -1.5f,    0.3f,    0.0f,
      -0.5f,    0.0f,    0.0f,
      -0.5f,    0.3f,    0.0f,

      // left wing start top
      -0.5f,    0.3f,   -0.3f,
      -1.3f,    0.3f,   -0.3f,
      -1.5f,    0.3f,    0.0f,
      -0.5f,    0.3f,   -0.3f,
      -1.5f,    0.3f,    0.0f,
      -0.5f,    0.3f,    0.0f,

      // left wing start front
      -0.5f,    0.3f,   -0.3f,
      -0.5f,    0.0f,   -0.3f,
      -1.3f,    0.0f,   -0.3f,
      -0.5f,    0.3f,   -0.3f,
      -1.3f,    0.0f,   -0.3f,
      -1.3f,    0.3f,   -0.3f,

      // left wing start bottom
      -0.5f,    0.0f,    0.0f,
      -1.5f,    0.0f,    0.0f,
      -1.3f,    0.0f,   -0.3f,
      -0.5f,    0.0f,    0.0f,
      -1.3f,    0.0f,   -0.3f,
      -0.5f,    0.0f,   -0.3f,

      // left wing end outside
      -1.5f,    0.3f,    0.0f,
      -2.2f,    0.15f,  -0.8f,
      -1.5f,    0.0f,    0.0f,

      // left wing end top
      -1.3f,    0.3f,   -0.3f,
      -2.2f,    0.15f,  -0.8f,
      -1.5f,    0.3f,    0.0f,

      // left wing end front
      -1.3f,    0.0f,   -0.3f,
      -2.2f,    0.15f,  -0.8f,
      -1.3f,    0.3f,   -0.3f,

      // left wing end bottom
      -1.5f,    0.0f,    0.0f,
      -2.2f,    0.15f,  -0.8f,
      -1.3f,    0.0f,   -0.3f,

      // right wing start back
      1.5f,    0.0f,    0.0f,
      1.5f,    0.3f,    0.0f,
      0.5f,    0.0f,    0.0f,
      0.5f,    0.0f,    0.0f,
      1.5f,    0.3f,    0.0f,
      0.5f,    0.3f,    0.0f,

      // right wing start top
      1.3f,    0.3f,   -0.3f,
      0.5f,    0.3f,   -0.3f,
      1.5f,    0.3f,    0.0f,
      1.5f,    0.3f,    0.0f,
      0.5f,    0.3f,   -0.3f,
      0.5f,    0.3f,    0.0f,

      // right wing start front
      0.5f,    0.0f,   -0.3f,
      0.5f,    0.3f,   -0.3f,
      1.3f,    0.0f,   -0.3f,
      1.3f,    0.0f,   -0.3f,
      0.5f,    0.3f,   -0.3f,
      1.3f,    0.3f,   -0.3f,

      // right wing start bottom
      1.5f,    0.0f,    0.0f,
      0.5f,    0.0f,    0.0f,
      1.3f,    0.0f,   -0.3f,
      1.3f,    0.0f,   -0.3f,
      0.5f,    0.0f,    0.0f,
      0.5f,    0.0f,   -0.3f,

      // right wing end outside
      2.2f,    0.15f,  -0.8f,
      1.5f,    0.3f,    0.0f,
      1.5f,    0.0f,    0.0f,

      // right wing end top
      2.2f,    0.15f,  -0.8f,
      1.3f,    0.3f,   -0.3f,
      1.5f,    0.3f,    0.0f,

      // right wing end front
      2.2f,    0.15f,  -0.8f,
      1.3f,    0.0f,   -0.3f,
      1.3f,    0.3f,   -0.3f,

      // right wing end bottom
      2.2f,    0.15f,  -0.8f,
      1.5f,    0.0f,    0.0f,
      1.3f,    0.0f,   -0.3f,
   };
   ship->colors = {
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,

      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,

      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,

      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,

      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,

      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,
      0.0f, 0.0f, 1.0f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,

      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
      0.0f, 0.0f, 0.3f,
   };
   ship->texcoords = { 0.0f };

   mat4 T_model = translate(mat4(1.0f), vec3(0.0f, -1.2f, 1.65f));
   mat4 R_model(1.0f);
   ship->model_base = T_model * R_model * scale(mat4(1.0f), vec3(0.1f, 0.1f, 0.1f));

   ship->translate_mat = T_model;

   initObject(ship);

   return ship;
}

/* LASER RENDERING/POSITIONING ALGORITHM
 * -Draw a thin rectangle for the laser beam, using the specified width and endpoints
 * -Texture the beam with a grayscale partially transparent image
 * -In the shader, blend the image with a color to support lasers of different colors
 *
 * The flat part of the textured rectangle needs to always face the camera, so the laser's width is constant
 * This is done as follows:
* -Determine the length of the laser based on the start and end points
* -Draw a rectangle along the z-axis and rotated upwards along the y-axis, with the correct final length and width
* -Rotate the beam around the z-axis by the correct angle, sot that in its final position, the flat part faces the camera
* -Rotate the beam along the x-axis and then along the y-axis and then translate it to put it into its final position
*/
// TODO: Make the color parameter have an effect
Laser* createLaser(vec3 start, vec3 end, vec3 color, GLfloat width) {
   Laser* obj = new Laser();
   obj->type = TYPE_LASER;
   obj->targetAsteroid = NULL;

   vec3 ray = end - start;
   float length = glm::length(ray);

   obj->points = {
       width / 2, 0.0f, -width / 2,
      -width / 2, 0.0f, -width / 2,
      -width / 2, 0.0f, 0.0f,
       width / 2, 0.0f, -width / 2,
      -width / 2, 0.0f, 0.0f,
       width / 2, 0.0f, 0.0f,
       width / 2, 0.0f, -length + width / 2,
      -width / 2, 0.0f, -length + width / 2,
      -width / 2, 0.0f, -width / 2,
       width / 2, 0.0f, -length + width / 2,
      -width / 2, 0.0f, -width / 2,
       width / 2, 0.0f, -width / 2,
       width / 2, 0.0f, -length,
      -width / 2, 0.0f, -length,
      -width / 2, 0.0f, -length + width / 2,
       width / 2, 0.0f, -length,
      -width / 2, 0.0f, -length + width / 2,
       width / 2, 0.0f, -length + width / 2,
   };

   obj->texcoords = {
      1.0f, 0.5f,
      0.0f, 0.5f,
      0.0f, 0.0f,
      1.0f, 0.5f,
      0.0f, 0.0f,
      1.0f, 0.0f,
      1.0f, 0.51f,
      0.0f, 0.51f,
      0.0f, 0.49f,
      1.0f, 0.51f,
      0.0f, 0.49f,
      1.0f, 0.49f,
      1.0f, 1.0f,
      0.0f, 1.0f,
      0.0f, 0.5f,
      1.0f, 1.0f,
      0.0f, 0.5f,
      1.0f, 0.5f,
   };

   float xAxisRotation = asin(ray.y / length);
   float yAxisRotation = atan2(-ray.x, -ray.z);

   vec3 normal(rotate(mat4(1.0f), yAxisRotation, vec3(0.0f, 1.0f, 0.0f)) *
               rotate(mat4(1.0f), xAxisRotation, vec3(1.0f, 0.0f, 0.0f)) *
               vec4(0.0f, 1.0f, 0.0f, 1.0f));

   // To project point P onto line AB:
   // projection = A + dot(AP,AB) / dot(AB,AB) * AB
   vec3 projOnLaser = start + glm::dot(cam_pos-start, ray) / (length*length) * ray;
   vec3 laserToCam = cam_pos - projOnLaser;

   float zAxisRotation = -atan2(glm::dot(glm::cross(normal, laserToCam), glm::normalize(ray)), glm::dot(normal, laserToCam));

   obj->model_base = rotate(mat4(1.0f), zAxisRotation, vec3(0.0f, 0.0f, 1.0f));

   initObject(obj);

   obj->model_transform = rotate(mat4(1.0f), xAxisRotation, vec3(1.0f, 0.0f, 0.0f)) * obj->model_transform;
   obj->model_transform = rotate(mat4(1.0f), yAxisRotation, vec3(0.0f, 1.0f, 0.0f)) * obj->model_transform;
   obj->model_transform = translate(mat4(1.0f), start) * obj->model_transform;

   return obj;
}

ShaderModelGroup createModelGroup(GLuint shaderProgram) {
   ShaderModelGroup smg;

   smg.shaderProgram = shaderProgram;
   glGenVertexArrays(1, &smg.vao);
   smg.numPoints = 0;

   return smg;
}

// TODO: Add the code to resize the buffers here
// addObjectToScene and removeObjectFromScene pretty much already do this.
// However, when addObjectToScene resizes the buffers, it resizes them for all object types
// It would be more efficient to only resize them for the object type in question

void removeModelFromGroup(ShaderModelGroup& modelGroup, SceneObject& model) {
   // TODO: Implement
}

void addModelToGroup(ShaderModelGroup& modelGroup, SceneObject& model) {
   // TODO: Implement
}

void defineModelGroupAttrib(ShaderModelGroup& modelGroup, string name, AttribType attribType,
                  GLint size, GLenum type, size_t fieldOffset) {
   if (type != GL_FLOAT && type != GL_UNSIGNED_INT) {
      cout << "Unknown shader program attribute type: " << type << endl;
      return;
   }

   AttribInfo attribInfo;

   attribInfo.attribType = attribType;
   attribInfo.index = modelGroup.attribs.size();
   attribInfo.size = size;
   attribInfo.type = type;
   attribInfo.fieldOffset = fieldOffset;

   modelGroup.attribs[name] = attribInfo;
}

void defineModelGroupUniform(ShaderModelGroup& modelGroup, string name, AttribType attribType,
                  GLint size, UniformType type, GLfloat* data) {
   AttribInfo attribInfo;

   attribInfo.attribType = attribType;
   attribInfo.size = size;
   attribInfo.uniType = type;
   attribInfo.data = data;

   modelGroup.attribs[name] = attribInfo;
}

void initModelGroupAttribs(ShaderModelGroup& modelGroup) {
   glBindVertexArray(modelGroup.vao);

   map<string, AttribInfo>::iterator it;
   for (it = modelGroup.attribs.begin(); it != modelGroup.attribs.end(); it++) {
      if (it->second.attribType == ATTRIB_UNIFORM) {
         it->second.buffer = glGetUniformLocation(modelGroup.shaderProgram, it->first.c_str());
      } else {
         glEnableVertexAttribArray(it->second.index);

         glGenBuffers(1, &it->second.buffer);
         glBindBuffer(GL_ARRAY_BUFFER, it->second.buffer);

         switch (it->second.type) {
            case GL_FLOAT: {
               glVertexAttribPointer(it->second.index, it->second.size, it->second.type, GL_FALSE, 0, NULL);
               break;
            }
            case GL_UNSIGNED_INT: {
               glVertexAttribIPointer(it->second.index, it->second.size, it->second.type, 0, NULL);
               break;
            }
         }
      }
   }
}

void bindUniformData(AttribInfo& attrib) {
   switch(attrib.uniType) {
      case UNIFORM_MATRIX_4F:
         glUniformMatrix4fv(attrib.buffer, attrib.size, GL_FALSE, attrib.data);
         break;
      case UNIFORM_1F:
         glUniform1fv(attrib.buffer, attrib.size, attrib.data);
         break;
      case UNIFORM_3F:
         glUniform3fv(attrib.buffer, attrib.size, attrib.data);
         break;
      case UNIFORM_NONE:
         break;
   }
}

void bindUniformData(AttribInfo& attrib, GLfloat *data) {
   switch(attrib.uniType) {
      case UNIFORM_MATRIX_4F:
         glUniformMatrix4fv(attrib.buffer, attrib.size, GL_FALSE, data);
         break;
      case UNIFORM_1F:
         glUniform1fv(attrib.buffer, attrib.size, data);
         break;
      case UNIFORM_3F:
         glUniform3fv(attrib.buffer, attrib.size, data);
         break;
      case UNIFORM_NONE:
         break;
   }
}

/* The purpose of this function is to replace the use of sizeof() when calling
 * function like glBufferSubData and using AttribInfo to get offsets and types
 * I need instead of hardcoding them. I can't save a type like GLfloat, but I cam
 * save GL_FLOAT and use this function to return sizeof(GLfloat) when GL_FLOAT is
 * passed.
 */
size_t GLsizeof(GLenum type) {
   switch (type) {
      case GL_FLOAT:
         return sizeof(GLfloat);
      case GL_UNSIGNED_INT:
         return sizeof(GLuint);
      default:
         cout << "Uknown GL type passed to GLsizeof: " << type << endl;
         return 0;
   }
}

/* This function returns a reference to the first element of a given vector
 * attribute in obj. The vector is assumed to hold GLfloats. If the same thing
 * needs to be done later for vectors of other types, we could pass in a GLenum,
 * and do something similar to GLsizeof
 */
GLvoid* getVectorAttribPtr(SceneObject& obj, size_t attribOffset) {
   return (GLvoid*)(&(*(vector<GLfloat>*)((size_t)&obj + attribOffset))[0]);
}

GLvoid* getScalarAttribPtr(SceneObject& obj, size_t attribOffset) {
   return (GLvoid*)((size_t)&obj + attribOffset);
}

void initializeParticleEffectBuffers(map<GLuint, BufferInfo>& shaderBufferInfo,
                  map<ObjectType, ShaderModelGroup>& modelGroups,
                  GLuint ubo) {
   float vv[EXPLOSION_PARTICLE_COUNT * 3]; // initial velocities vec3
   float vt[EXPLOSION_PARTICLE_COUNT]; // initial times
   float t_accum = 0.0f; // start time

   for (int i = 0; i < EXPLOSION_PARTICLE_COUNT; i++) {
      vt[i] = t_accum;
      t_accum += 0.01f;

      float randx = ((float)rand() / (float)RAND_MAX) - 0.5f;
      float randy = ((float)rand() / (float)RAND_MAX) - 0.5f;
      vv[i*3] = randx;
      vv[i*3 + 1] = randy;
      vv[i*3 + 2] = 0.0f;
   }

   glUseProgram(modelGroups[TYPE_EXPLOSION].shaderProgram);

   bindUniformData(modelGroups[TYPE_EXPLOSION].attribs["proj"]);
   bindUniformData(modelGroups[TYPE_EXPLOSION].attribs["view"]);

   // the glBufferData calls need to stay here while the corresponding arrays
   // are local to this function. Once they're made part of the explosion object, I might be able
   // to move this code out of here

   glBindBuffer(GL_ARRAY_BUFFER, modelGroups[TYPE_EXPLOSION].attribs["v_i"].buffer);
   glBufferData(GL_ARRAY_BUFFER, sizeof(vv), vv, GL_STATIC_DRAW);

   glBindBuffer(GL_ARRAY_BUFFER, modelGroups[TYPE_EXPLOSION].attribs["start_time"].buffer);
   glBufferData(GL_ARRAY_BUFFER, sizeof(vt), vt, GL_STATIC_DRAW);

   // TODO: createExplosion should take the velocities and times as arguments and copy them to the explosion object
   // That way, this function could maybe be called every time a new explosion is created
   objExplosion = createExplosion();
   addObjectToScene(objExplosion, shaderBufferInfo, modelGroups, ubo);
}

void populateBuffers(vector<SceneObject*>& objects,
                  map<GLuint, BufferInfo>& shaderBufferInfo,
                  map<ObjectType, ShaderModelGroup>& modelGroups,
                  GLuint ubo) {
   GLsizeiptr num_points = 0;
   GLsizeiptr num_objects = 0;

   map<GLuint, unsigned int> shaderCounts;
   map<GLuint, unsigned int> shaderUboCounts;

   map<GLuint, BufferInfo>::iterator shaderIt;

   for (shaderIt = shaderBufferInfo.begin(); shaderIt != shaderBufferInfo.end(); shaderIt++) {
      shaderCounts[shaderIt->first] = 0;
      shaderUboCounts[shaderIt->first] = 0;
   }

   vector<SceneObject*>::iterator it;

   /* Find all shaders that need to be used and the number of objects and
   * number of points for each shader. Construct a map from shader id to count
   * of points being drawn using that shader (for thw model matrix ubo, we
   * need object counts instead). These will be used to get offsets into the
   * vertex buffer for each shader.
   */
   for (it = objects.begin(); it != objects.end(); ) {
      if ((*it)->deleted) {
         delete *it;
         it = objects.erase(it);
      } else {
         num_points += (*it)->num_points;
         num_objects++;

         shaderCounts[modelGroups[(*it)->type].shaderProgram] += (*it)->num_points;
         shaderUboCounts[modelGroups[(*it)->type].shaderProgram]++;

         it++;
      }
   }

   // double the buffer sizes to leave room for new objects
   num_points *= 2;
   num_objects *= 2;

   map<GLuint, unsigned int>::iterator shaderCountIt;
   unsigned int lastShaderCount = 0;
   unsigned int lastShaderUboCount = 0;

   /*
   * The counts calculated above can be used to get the starting offset of
   * each shader in the vertex buffer. Create a map of base offsets to mark
   * where the data for the first object using a given shader begins. Also,
   * create a map of current offsets to mark where to copy data for the next
   * object being added.
   */
   for (shaderCountIt = shaderCounts.begin(); shaderCountIt != shaderCounts.end(); shaderCountIt++) {
      // When populating the buffers, leave as much empty space as space taken up by existing objects
      // to allow new objects to be added without immediately having to resize the buffers
      shaderBufferInfo[shaderCountIt->first].vbo_base = lastShaderCount * 2;
      shaderBufferInfo[shaderCountIt->first].ubo_base = lastShaderUboCount * 2;

      shaderBufferInfo[shaderCountIt->first].ubo_offset = 0;

      shaderBufferInfo[shaderCountIt->first].ubo_capacity = shaderUboCounts[shaderCountIt->first] * 2;

      lastShaderCount += shaderCounts[shaderCountIt->first];
      lastShaderUboCount += shaderUboCounts[shaderCountIt->first];
   }

   map<ObjectType, ShaderModelGroup>::iterator modelGroupIt;
   ShaderModelGroup* smg;
   for (modelGroupIt = modelGroups.begin(); modelGroupIt != modelGroups.end(); modelGroupIt++) {
      smg = &modelGroups[modelGroupIt->first];

      smg->numPoints = 0;
      smg->vboCapacity = shaderCounts[smg->shaderProgram] * 2;

      AttribInfo* attrib;

      if (modelGroupIt->first == TYPE_SHIP) {
         attrib = &smg->attribs["vertex_position"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);

         attrib = &smg->attribs["vertex_color"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);

         attrib = &smg->attribs["vertex_normal"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);

         attrib = &smg->attribs["ubo_index"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);
      } else if (modelGroupIt->first == TYPE_ASTEROID) {
         attrib = &smg->attribs["vertex_position"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);

         attrib = &smg->attribs["vertex_color"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);

         attrib = &smg->attribs["vertex_normal"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);

         attrib = &smg->attribs["ubo_index"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);
      } else if (modelGroupIt->first == TYPE_LASER) {
         attrib = &smg->attribs["vertex_position"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);

         attrib = &smg->attribs["vt"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);

         attrib = &smg->attribs["ubo_index"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);
      } else if (modelGroupIt->first == TYPE_EXPLOSION) {
         attrib = &smg->attribs["ubo_index"];
         glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
         glBufferData(GL_ARRAY_BUFFER, smg->vboCapacity * GLsizeof(attrib->type) * attrib->size, NULL, GL_DYNAMIC_DRAW);
      }

      // TODO: I could move the glBufferData calls for explosions here and call glBufferSubData in copyObjectDataToBuffers
      // To make this work, I would need to store the explosion points and times in the explosion object so I could then copy
      // them to the buffers.
      // Also, confirm that rendering multiple exxplosions would be feasible. They might need different curTimes
      // Also, store the explosion model mat(s) in the global ubo, just like all other objects
      // This should just require setting their ubo_offset correctly
      // (This already seems to be happening. I think I just need to add a ubo index buffer to explosions)
   }

   // Allocate the ubo using the counts calculated above

   glBindBuffer(GL_UNIFORM_BUFFER, ubo);
   glBufferData(GL_UNIFORM_BUFFER, num_objects * sizeof(mat4), NULL, GL_DYNAMIC_DRAW);

   for (it = objects.begin(); it != objects.end(); it++) {
      copyObjectDataToBuffers(**it, shaderBufferInfo, modelGroups, ubo);
   }
}

void copyObjectDataToBuffers(SceneObject& obj,
                  map<GLuint, BufferInfo>& shaderBufferInfo,
                  map<ObjectType, ShaderModelGroup>& modelGroups,
                  GLuint ubo) {
   BufferInfo* bufferInfo = &shaderBufferInfo[modelGroups[obj.type].shaderProgram];

   obj.vertex_vbo_offset = modelGroups[obj.type].numPoints;
   obj.ubo_offset = bufferInfo->ubo_base + bufferInfo->ubo_offset;

   ShaderModelGroup& smg = modelGroups[obj.type];

   for (map<string, AttribInfo>::iterator it = smg.attribs.begin(); it != smg.attribs.end(); it++) {
      glBindBuffer(GL_ARRAY_BUFFER, it->second.buffer);

      if (obj.type != TYPE_EXPLOSION || it->first == "ubo_index") {
         switch (it->second.attribType) {
            case ATTRIB_POINT_VARYING:
               glBufferSubData(GL_ARRAY_BUFFER, obj.vertex_vbo_offset * GLsizeof(it->second.type) * it->second.size,
                  obj.num_points * GLsizeof(it->second.type) * it->second.size, getVectorAttribPtr(obj, it->second.fieldOffset));
               break;
            case ATTRIB_OBJECT_VARYING:
               for (unsigned int i = 0; i < obj.num_points; i++) {
                  glBufferSubData(GL_ARRAY_BUFFER, (obj.vertex_vbo_offset + i) * GLsizeof(it->second.type) * it->second.size,
                     GLsizeof(it->second.type) * it->second.size, getScalarAttribPtr(obj, it->second.fieldOffset));
               }
               break;
            case ATTRIB_UNIFORM:
               break;
         }
      }
   }

   if (obj.type != TYPE_EXPLOSION) {
      obj.model_mat = obj.model_transform * obj.model_base;
   }

   glBindBuffer(GL_UNIFORM_BUFFER, ubo);
   glBufferSubData(GL_UNIFORM_BUFFER, obj.ubo_offset * sizeof(mat4), sizeof(mat4), value_ptr(obj.model_mat));

   if (obj.type == TYPE_ASTEROID) {
      glUseProgram(modelGroups[TYPE_ASTEROID].shaderProgram);

      ostringstream oss;
      oss << "hp[" << obj.ubo_offset << "]";
      glUniform1f(glGetUniformLocation(modelGroups[TYPE_ASTEROID].shaderProgram, oss.str().c_str()), ((Asteroid*)&obj)->hp);
   }

   modelGroups[obj.type].numPoints += obj.num_points;
   bufferInfo->ubo_offset++;
}

void transformObject(SceneObject& obj, const mat4& transform, GLuint ubo) {
   if (obj.deleted) return;

   obj.model_transform = transform * obj.model_transform;
   obj.model_mat = obj.model_transform * obj.model_base;

   obj.bounding_center = vec3(transform * vec4(obj.bounding_center, 1.0f));

   glBindBuffer(GL_UNIFORM_BUFFER, ubo);
   glBufferSubData(GL_UNIFORM_BUFFER, obj.ubo_offset * sizeof(mat4), sizeof(mat4), value_ptr(obj.model_mat));
}

void translateLaser(Laser* laser, const vec3& translation, GLuint ubo) {
   // TODO: A lot of the values calculated here can be calculated once and saved when the laser is created,
   // and then re-used here

   vec3 start = vec3(laser->model_transform * vec4(0.0f, 0.0f, 0.0f, 1.0f));
   vec3 end = vec3(laser->model_transform * vec4(0.0f, 0.0f, laser->points[38], 1.0f));

   vec3 ray = end - start;
   float length = glm::length(ray);

   float xAxisRotation = asin(ray.y / length);
   float yAxisRotation = atan2(-ray.x, -ray.z);

   vec3 normal(rotate(mat4(1.0f), yAxisRotation, vec3(0.0f, 1.0f, 0.0f)) *
      rotate(mat4(1.0f), xAxisRotation, vec3(1.0f, 0.0f, 0.0f)) *
      vec4(0.0f, 1.0f, 0.0f, 1.0f));

   // To project point P onto line AB:
   // projection = A + dot(AP,AB) / dot(AB,AB) * AB
   vec3 projOnLaser = start + glm::dot(cam_pos - start, ray) / (length*length) * ray;
   vec3 laserToCam = cam_pos - projOnLaser;

   float zAxisRotation = -atan2(glm::dot(glm::cross(normal, laserToCam), glm::normalize(ray)), glm::dot(normal, laserToCam));

   laser->model_base = rotate(mat4(1.0f), zAxisRotation, vec3(0.0f, 0.0f, 1.0f));

   transformObject(*laser, translate(mat4(1.0f), translation), ubo);
}

void updateLaserTarget(Laser* laser, vector<SceneObject*>& objects, ShaderModelGroup& laserSmg, GLuint asteroid_sp) {
   // TODO: A lot of the values calculated here can be calculated once and saved when the laser is created,
   // and then re-used here

   vec3 start = vec3(laser->model_transform * vec4(0.0f, 0.0f, 0.0f, 1.0f));
   vec3 end = vec3(laser->model_transform * vec4(0.0f, 0.0f, laser->points[2] + laser->points[20], 1.0f));

   vec3 intersection(0.0f), closestIntersection(0.0f);
   Asteroid* closestAsteroid = NULL;

   for (vector<SceneObject*>::iterator it = objects.begin(); it != objects.end(); it++) {
      if ((*it)->type == TYPE_ASTEROID && !(*it)->deleted && getLaserAndAsteroidIntersection(start, end, **it, intersection)) {
         // TODO: Implement a more generic algorithm for testing the closest object by getting the distance between the points
         if (closestAsteroid == NULL || intersection.z > closestIntersection.z) {
            // TODO: At this point, find the real intersection of the laser with one of the asteroid's sides
            closestAsteroid = (Asteroid*)*it;
            closestIntersection = intersection;
         }
      }
   }

   float width = laser->points[0] - laser->points[2];

   if (laser->targetAsteroid != closestAsteroid) {
      if (laser->targetAsteroid != NULL) {
         if (laser == leftLaser) {
            leftLaserEffect->deleted = true;
         } else if (laser == rightLaser) {
            rightLaserEffect->deleted = true;
         }
      }

      EffectOverTime* eot = NULL;

      if (closestAsteroid != NULL) {
         eot = new EffectOverTime(closestAsteroid->hp, -20.0f, closestAsteroid);
         effects.push_back(eot);
      }

      if (laser == leftLaser) {
         leftLaserEffect = eot;
      } else if (laser == rightLaser) {
         rightLaserEffect = eot;
      }
   }
   laser->targetAsteroid = closestAsteroid;

   float length = 5.24f; // I think this was to make sure the laser went past the end of the screen
   if (closestAsteroid != NULL) {
      length = glm::length(closestIntersection - start);

      // TODO: Find a more generic way of updating the asteroid hp than in updateLaserTarget

      glUseProgram(asteroid_sp);

      ostringstream oss;
      oss << "hp[" << closestAsteroid->ubo_offset << "]";
      glUniform1f(glGetUniformLocation(asteroid_sp, oss.str().c_str()), closestAsteroid->hp);
   }

   laser->points[20] = -length + width / 2;
   laser->points[23] = -length + width / 2;
   laser->points[29] = -length + width / 2;
   laser->points[38] = -length;
   laser->points[41] = -length;
   laser->points[44] = -length + width / 2;
   laser->points[47] = -length;
   laser->points[50] = -length + width / 2;
   laser->points[53] = -length + width / 2;

   AttribInfo* attrib = &laserSmg.attribs["vertex_position"];
   glBindBuffer(GL_ARRAY_BUFFER, attrib->buffer);
   glBufferSubData(GL_ARRAY_BUFFER, laser->vertex_vbo_offset * GLsizeof(attrib->type) * attrib->size,
      laser->num_points * GLsizeof(attrib->type) * attrib->size, getVectorAttribPtr(*laser, attrib->fieldOffset));
}

bool getLaserAndAsteroidIntersection(vec3& start, vec3& end, SceneObject& asteroid, vec3& intersection) {
   /*
   ### LINE EQUATIONS ###
   x = x1 + u * (x2 - x1)
   y = y1 + u * (y2 - y1)
   z = z1 + u * (z2 - z1)

   ### SPHERE EQUATION ###
   (x - x3)^2 + (y - y3)^2 + (z - z3)^2 = r^2

   ### QUADRATIC EQUATION TO SOLVE ###
   a*u^2 + b*u + c = 0
   WHERE THE CONSTANTS ARE
   a = (x2 - x1)^2 + (y2 - y1)^2 + (z2 - z1)^2
   b = 2*( (x2 - x1)*(x1 - x3) + (y2 - y1)*(y1 - y3) + (z2 - z1)*(z1 - z3) )
   c = x3^2 + y3^2 + z3^2 + x1^2 + y1^2 + z1^2 - 2(x3*x1 + y3*y1 + z3*z1) - r^2

   u = (-b +- sqrt(b^2 - 4*a*c)) / 2a

   If the value under the root is >= 0, we got an intersection
   If the value > 0, there are two solutions. Take the one closer to 0, since that's the
   one closer to the laser start point
   */

   vec3& center = asteroid.bounding_center;

   float a = pow(end.x-start.x, 2) + pow(end.y-start.y, 2) + pow(end.z-start.z, 2);
   float b = 2*((start.x-end.x)*(start.x-center.x) + (end.y-start.y)*(start.y-center.y) + (end.z-start.z)*(start.z-center.z));
   float c = pow(center.x, 2) + pow(center.y, 2) + pow(center.z, 2) + pow(start.x, 2) + pow(start.y, 2) + pow(start.z, 2) - 2*(center.x*start.x + center.y*start.y + center.z*start.z) - pow(asteroid.bounding_radius, 2);
   float discriminant = pow(b, 2) - 4*a*c;

   if (discriminant >= 0.0f) {
      // In this case, the negative root will always give the point closer to the laser start point
      float u = (-b - sqrt(discriminant)) / (2 * a);

      // Check that the intersection is within the line segment corresponding to the laser
      if (0.0f <= u && u <= 1.0f) {
         intersection = start + u * (end - start);
         return true;
      }
   }

   return false;
}

void renderScene(map<GLuint, BufferInfo>& shaderBufferInfo,
                  map<ObjectType, ShaderModelGroup>& modelGroups, GLuint ubo) {

   glUseProgram(modelGroups[TYPE_SHIP].shaderProgram);
   glBindVertexArray(modelGroups[TYPE_SHIP].vao);

   glDrawArrays(GL_TRIANGLES, 0, modelGroups[TYPE_SHIP].numPoints);

   glUseProgram(modelGroups[TYPE_ASTEROID].shaderProgram);
   glBindVertexArray(modelGroups[TYPE_ASTEROID].vao);

   glDrawArrays(GL_TRIANGLES, 0, modelGroups[TYPE_ASTEROID].numPoints);

   glEnable(GL_BLEND);

   glUseProgram(modelGroups[TYPE_LASER].shaderProgram);
   glBindVertexArray(modelGroups[TYPE_LASER].vao);

   glDrawArrays(GL_TRIANGLES, 0, modelGroups[TYPE_LASER].numPoints);

   glUseProgram(modelGroups[TYPE_EXPLOSION].shaderProgram);
   glBindVertexArray(modelGroups[TYPE_EXPLOSION].vao);

   glEnable(GL_PROGRAM_POINT_SIZE);

   glDrawArrays(GL_POINTS, 0, modelGroups[TYPE_EXPLOSION].numPoints);

   glDisable(GL_PROGRAM_POINT_SIZE);
   glDisable(GL_BLEND);
}

void renderSceneGui(map<string, vector<UIValue>> valueLists) {
   ImGui_ImplGlfwGL3_NewFrame();

   // 1. Show a simple window.
   // Tip: if we don't call ImGui::Begin()/ImGui::End() the widgets automatically appears in a window called "Debug".
   /*
   {
      static float f = 0.0f;
      static int counter = 0;
      ImGui::Text("Hello, world!");                           // Display some text (you can use a format string too)
      ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f    
      ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color

      ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our windows open/close state
      ImGui::Checkbox("Another Window", &show_another_window);

      if (ImGui::Button("Button"))                            // Buttons return true when clicked (NB: most widgets return true when edited/activated)
         counter++;
      ImGui::SameLine();
      ImGui::Text("counter = %d", counter);

      ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
   }
   */

   {
      ImGui::SetNextWindowSize(ImVec2(95, 46), ImGuiCond_Once);
      ImGui::SetNextWindowPos(ImVec2(10, 50), ImGuiCond_Once);
      ImGui::Begin("WndStats", NULL,
         ImGuiWindowFlags_NoTitleBar |
         ImGuiWindowFlags_NoResize |
         ImGuiWindowFlags_NoMove);

      renderGuiValueList(valueLists["stats value list"]);

      ImGui::End();
   }

   {
      ImGui::SetNextWindowSize(ImVec2(250, 35), ImGuiCond_Once);
      ImGui::SetNextWindowPos(ImVec2(380, 10), ImGuiCond_Once);
      ImGui::Begin("WndMenubar", NULL,
         ImGuiWindowFlags_NoTitleBar |
         ImGuiWindowFlags_NoResize |
         ImGuiWindowFlags_NoMove);
      ImGui::InvisibleButton("", ImVec2(155, 18));
      ImGui::SameLine();
      if (ImGui::Button("Main Menu")) {
         events.push(EVENT_GO_TO_MAIN_MENU);
      }
      ImGui::End();
   }

   {
      ImGui::SetNextWindowSize(ImVec2(200, 200), ImGuiCond_Once);
      ImGui::SetNextWindowPos(ImVec2(430, 60), ImGuiCond_Once);
      ImGui::Begin("WndDebug", NULL,
         ImGuiWindowFlags_NoTitleBar |
         ImGuiWindowFlags_NoResize |
         ImGuiWindowFlags_NoMove);

      renderGuiValueList(valueLists["debug value list"]);

      ImGui::End();
   }

   ImGui::Render();
   ImGui_ImplGlfwGL3_RenderDrawData(ImGui::GetDrawData());
}

void renderMainMenu() {
}

void renderMainMenuGui() {
   ImGui_ImplGlfwGL3_NewFrame();

   {
      int padding = 4;
      ImGui::SetNextWindowPos(ImVec2(-padding, -padding), ImGuiCond_Once);
      ImGui::SetNextWindowSize(ImVec2(width + 2 * padding, height + 2 * padding), ImGuiCond_Once);
      ImGui::Begin("WndMain", NULL,
         ImGuiWindowFlags_NoTitleBar |
         ImGuiWindowFlags_NoResize |
         ImGuiWindowFlags_NoMove);

      ImGui::InvisibleButton("", ImVec2(10, 80));
      ImGui::InvisibleButton("", ImVec2(285, 18));
      ImGui::SameLine();
      if (ImGui::Button("New Game")) {
         events.push(EVENT_GO_TO_GAME);
      }

      ImGui::InvisibleButton("", ImVec2(10, 15));
      ImGui::InvisibleButton("", ImVec2(300, 18));
      ImGui::SameLine();
      if (ImGui::Button("Quit")) {
         events.push(EVENT_QUIT);
      }

      ImGui::End();
   }

   ImGui::Render();
   ImGui_ImplGlfwGL3_RenderDrawData(ImGui::GetDrawData());
}

void initGuiValueLists(map<string, vector<UIValue>> valueLists) {
   valueLists["stats value list"] = vector<UIValue>();
   valueLists["debug value list"] = vector<UIValue>();
}

void renderGuiValueList(vector<UIValue>& values) {
   float maxWidth = 0.0f;
   float cursorStartPos = ImGui::GetCursorPosX();

   for (vector<UIValue>::iterator it = values.begin(); it != values.end(); it++) {
      float textWidth = ImGui::CalcTextSize(it->label.c_str()).x;

      if (maxWidth < textWidth)
         maxWidth = textWidth;
   }

   stringstream ss;

   for (vector<UIValue>::iterator it = values.begin(); it != values.end(); it++) {
      ss.str("");
      ss.clear();

      switch (it->type) {
         case UIVALUE_INT:
            ss << it->label << ": " << *(unsigned int*)it->value;
            break;
         case UIVALUE_DOUBLE:
            ss << it->label << ": " << *(double*)it->value;
            break;
      }

      float textWidth = ImGui::CalcTextSize(it->label.c_str()).x;

      ImGui::SetCursorPosX(cursorStartPos + maxWidth - textWidth);
      ImGui::Text("%s", ss.str().c_str());
   }
}

Asteroid* createAsteroid(vec3 pos) {
   Asteroid* obj = new Asteroid();
   obj->type = TYPE_ASTEROID;
   obj->hp = 10.0f;

   obj->points = {
      // front
      1.0f,  1.0f,  1.0f,
      -1.0f,  1.0f,  1.0f,
      -1.0f, -1.0f,  1.0f,
      1.0f,  1.0f,  1.0f,
      -1.0f, -1.0f,  1.0f,
      1.0f, -1.0f,  1.0f,

      // top
      1.0f,  1.0f, -1.0f,
      -1.0f,  1.0f, -1.0f,
      -1.0f,  1.0f,  1.0f,
      1.0f,  1.0f, -1.0f,
      -1.0f,  1.0f,  1.0f,
      1.0f,  1.0f,  1.0f,

      // bottom
      1.0f, -1.0f,  1.0f,
      -1.0f, -1.0f,  1.0f,
      -1.0f, -1.0f, -1.0f,
      1.0f, -1.0f,  1.0f,
      -1.0f, -1.0f, -1.0f,
      1.0f, -1.0f, -1.0f,

      // back
      1.0f,  1.0f, -1.0f,
      -1.0f, -1.0f, -1.0f,
      -1.0f,  1.0f, -1.0f,
      1.0f,  1.0f, -1.0f,
      1.0f, -1.0f, -1.0f,
      -1.0f, -1.0f, -1.0f,

      // right
      1.0f,  1.0f, -1.0f,
      1.0f,  1.0f,  1.0f,
      1.0f, -1.0f,  1.0f,
      1.0f,  1.0f, -1.0f,
      1.0f, -1.0f,  1.0f,
      1.0f, -1.0f, -1.0f,

      // left
      -1.0f,  1.0f,  1.0f,
      -1.0f,  1.0f, -1.0f,
      -1.0f, -1.0f, -1.0f,
      -1.0f,  1.0f,  1.0f,
      -1.0f, -1.0f, -1.0f,
      -1.0f, -1.0f,  1.0f,
   };
   obj->colors = {
      // front
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,

      // top
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,

      // bottom
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,

      // back
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,

      // right
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,

      // left
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
      0.4f, 0.4f, 0.4f,
   };
   obj->texcoords = { 0.0f };

   mat4 T = translate(mat4(1.0f), pos);
   mat4 R = rotate(mat4(1.0f), 60.0f * (float)ONE_DEG_IN_RAD, vec3(1.0f, 1.0f, -1.0f));
   obj->model_base = T * R * scale(mat4(1.0f), vec3(0.1f, 0.1f, 0.1f));

   obj->translate_mat = T;

   initObject(obj);
   // This accounts for the scaling in model_base.
   // Dividing by 8 instead of 10 since the bounding radius algorithm
   // under-calculates the true value.
   // TODO: Once the intersection check with the sides of the asteroid is done,
   // this can be removed.
   obj->bounding_radius /= 8.0f;

   return obj;
}

ParticleEffect* createExplosion() {
   ParticleEffect* obj = new ParticleEffect();
   obj->type = TYPE_EXPLOSION;

   obj->points = {};
   obj->colors = {};

   initObject(obj);
   obj->num_points = EXPLOSION_PARTICLE_COUNT;

   return obj;
}

float getRandomNum(float low, float high) {
   return low + ((float)rand() / RAND_MAX) * (high-low);
}