path: root/source/lessons/uniform buffer objects/main.cpp

#include <stdio.h>
#include <SDL2/SDL.h>
#include <glad/glad.h>
#include <assimp/Importer.hpp>
#include <assimp/scene.h>
#include <assimp/postprocess.h>
#include <vector>

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

/* @lookup:
*  - understand kernals, how they work and how they affect post processing
*  - Check to see why it is necessary to do glBindTexture() 
*    - understand the difference between binding textures, and activating a texture unit
*  - I do not understand how floating point numbers work, so I should probably look into that.
*	 - The normal matrix calculation in the fragment shader for the object affected by light has been mainly copied.
*		 I have tried to understand the formula, and whilst it made some sense, it is not fully clear to me, and I cannot picture it yet.
*		 Revisit the derivation for the normal matrix some time in the future.
*  - Lookup the derivation of the formula for reflecting a vector about a normal. I am doing that for specular lighting, but the learnopengl tutorial
*		 just uses a glsl reflect formula, and at the time of writing it is also very late so I am not in the mood or position to look into it at present.
*  - One of the things I have observed with specular lights is that the circle/specular highlight follows the camera (me) when I move. I would like to figure
*		 out a way by which this does not happen and it remains fixed on the object, at the angle at which it hits. All of this will be made complicated by the fact
*		 that ofcourse everything is actually happening from the cameras' perspective. I would still love to figure this out.
*/

typedef uint8_t   u8;
typedef uint16_t u16;
typedef uint32_t u32;
typedef uint64_t u64;

typedef int8_t    s8;
typedef int16_t  s16;
typedef int32_t  s32;
typedef int64_t  s64;

typedef float    r32;
typedef double   r64;

typedef u8        b8;

#include "math.h"

// =========== Shader Loading =============

unsigned int gl_create_vertex_shader(char* vertex_shader_source)
{
	unsigned int vertex_shader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertex_shader, 1, &vertex_shader_source, NULL);
	glCompileShader(vertex_shader);
    
	int success;
	char info_log[512];
	glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertex_shader, 512, NULL, info_log);
		printf("================================\n");
		printf("vertex shader compilation failed:\n%s\n", info_log);
	}
    
	return vertex_shader;
}

unsigned int gl_create_fragment_shader(char* fragment_shader_source)
{
	unsigned int fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragment_shader, 1, &fragment_shader_source, NULL);
	glCompileShader(fragment_shader);
    
	int success;
	char info_log[512];
	glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragment_shader, 512, NULL, info_log);
		printf("================================\n");
		printf("fragment shader compilation failed:\n%s\n", info_log);
	}
    
	return fragment_shader;
}

unsigned int gl_create_shader_program(unsigned int vertex_shader, unsigned int fragment_shader)
{
	unsigned int shader_program = glCreateProgram();
    
	glAttachShader(shader_program, vertex_shader);
	glAttachShader(shader_program, fragment_shader);
	glLinkProgram(shader_program);
    
	int success;
	char info_log[512];
	glGetProgramiv(shader_program, GL_LINK_STATUS, &success);
	if (!success)
	{
		glGetProgramInfoLog(shader_program, 512, NULL, info_log);
		printf("================================\n");
		printf("shader program linking failed:\n%s\n", info_log);
	}
    
	glDeleteShader(vertex_shader);
	glDeleteShader(fragment_shader);
    
	return shader_program;
}

unsigned int gl_shader_program(char* vertex_shader_source, char* fragment_shader_source)
{
  unsigned int vertex_shader = gl_create_vertex_shader(vertex_shader_source);
  unsigned int fragment_shader = gl_create_fragment_shader(fragment_shader_source);
  unsigned int shader_program = gl_create_shader_program(vertex_shader, fragment_shader);

  return shader_program;
}

Mat4 camera_create4m(Vec3 camera_pos, Vec3 camera_look, Vec3 camera_up)
{
	// @note: We do this because this allows the camera to have the axis it looks at
	// inwards be the +z axis.
	// If we did not do this, then the inward axis the camera looks at would be negative. 
	// I am still learning from learnopengl.com but I imagine that this was done for conveniences' sake.
	Vec3 camera_forward_dir = normalize3v(subtract3v(camera_pos, camera_look));
	Vec3 camera_right_dir   = normalize3v(cross_multiply3v(camera_up, camera_forward_dir));
	Vec3 camera_up_dir      = normalize3v(cross_multiply3v(camera_forward_dir, camera_right_dir));
    
	Mat4 res = lookat4m(camera_up_dir, camera_forward_dir, camera_right_dir, camera_pos);
    
	return res;
}

Vec3 camera_look_around(r32 angle_pitch, r32 angle_yaw)
{
    Vec3 camera_look = {0.0};
    camera_look.x = cosf(angle_yaw) * cosf(angle_pitch);
    camera_look.y = sinf(angle_pitch);
    camera_look.z = sinf(angle_yaw) * cosf(angle_pitch);
    camera_look = normalize3v(camera_look);
    
    return camera_look;
}

s32 gl_load_texture(u32 texture_id, const char* path)
{
  s32 width, height, nrChannels;
  unsigned char *data = stbi_load(path, &width, &height, &nrChannels, 0);
  if (data)
  {
    GLenum format;
    if (nrChannels == 1)
      format = GL_RED;
    else if (nrChannels == 3)
      format = GL_RGB;
    else if (nrChannels == 4)
      format = GL_RGBA;

    glBindTexture(GL_TEXTURE_2D, texture_id);
    glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    stbi_image_free(data);
  }
  else
  {
    printf("failed to load image texture at path: %s", path);
    stbi_image_free(data);
  }

  return texture_id;
}

// =================== Model Loading ========================
// This section contains a whole host of things:
// 1. classes
// 2. std::vectors
// 3. std::strings
// that I have only used as a glue for I did not know if I had the model loading setup properly.
// @todo: replace these things eventually. For now the goal is to complete learnopengl

s32 TextureFromFile(const char* filepath, std::string directory)
{
  // @note: this function is stupid as it already became outdated as I needed to tweak the parameters
  // for wrapping. Either those become function parameters (Which makes sense I guess) or I look at
  // exactly what steps I am reusing and just make that a function so the function is called fewer times.
  //
  // I am guessing this won't look good from a design point of view for all those jobs and postings, even if
  // this may be the simpler and faster thing to do, albeit at the cost of typing.
  std::string filename = std::string(filepath);
  filename = directory + '/' + filename;

  u32 texid;
  glGenTextures(1, &texid);

  s32 width, height, nrChannels;
  unsigned char *data = stbi_load(filename.c_str(), &width, &height, &nrChannels, 0);
  if (data)
  {
    GLenum format;
    if (nrChannels == 1)
      format = GL_RED;
    else if (nrChannels == 3)
      format = GL_RGB;
    else if (nrChannels == 4)
      format = GL_RGBA;

    glBindTexture(GL_TEXTURE_2D, texid);
    glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    stbi_image_free(data);
  }
  else
  {
    printf("failed to load image texture at path: %s", filepath);
    stbi_image_free(data);
  }

  return texid;
}

enum TextureType { TextureDiffuse=0, TextureSpecular };

struct Vertex {
  Vec3 position;
  Vec3 normal;
  Vec2 texture;
};

struct Texture {
  u32 id;
  enum TextureType type;
  std::string fname;
};

class Mesh {
  public:
  std::vector<Vertex>  vertices;
  std::vector<u32> indices;
  std::vector<Texture> textures;

  u32 vao;
  u32 vbo;
  u32 ebo;

  Mesh(std::vector<Vertex> vertices, std::vector<u32> indices, std::vector<Texture> textures)
  {
    this->vertices = vertices;
    this->indices = indices;
    this->textures = textures;

    // setup mesh shader stuff
    glGenVertexArrays(1, &vao);
    glGenBuffers(1, &vbo);
    glGenBuffers(1, &ebo);

    glBindVertexArray(vao);

    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, this->vertices.size() * sizeof(struct Vertex), &(this->vertices[0]), GL_STATIC_DRAW);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, this->indices.size() * sizeof(u32), &(this->indices[0]), GL_STATIC_DRAW);

    // position
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)0);
    // normal
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, normal));
    // texture
    glEnableVertexAttribArray(2);
    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, texture));

    glBindVertexArray(0);
  }

  void draw(u32 shader_program)
  {
    glUseProgram(shader_program);

    u32 diffuse_num = 1;
    u32 specular_num = 1;
    char tex_unit_name[64];
    // set shininess
    s32 mat_shine_loc = glGetUniformLocation(shader_program, "material.shininess");
    glUniform1f(mat_shine_loc, 32.0f);

    for (u32 i=0; i<textures.size(); i++)
    {
      struct Texture curr_tex = textures[i];
      if (curr_tex.type == TextureDiffuse)
      {
        sprintf(tex_unit_name, "material.diffuse[%i]", diffuse_num);
      }
      else if (curr_tex.type == TextureSpecular)
      {
        sprintf(tex_unit_name, "material.diffuse[%i]", specular_num);
      }

      glActiveTexture(GL_TEXTURE0 + i);
      s32 tex_unit_loc = glGetUniformLocation(shader_program, tex_unit_name);
      glUniform1i(tex_unit_loc, i);
      glBindTexture(GL_TEXTURE_2D, curr_tex.id);
    }
    glActiveTexture(GL_TEXTURE0);

    glBindVertexArray(vao);
    glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, 0);
    glBindVertexArray(0);
  }
};

class Model
{
  public:
    Model(std::string path)
    {
      load_model(path);
    }
    void draw(u32 shader_program);
  private:
    std::vector<Texture> loaded_textures;
    std::vector<Mesh> meshes;
    std::string directory;

    void load_model(std::string path);
    void process_node(aiNode *node, const aiScene *scene);
    Mesh process_mesh(aiMesh *mesh, const aiScene *scene);
    std::vector<Texture> load_material_textures(aiMaterial *mat, aiTextureType type, TextureType type_name);
};

void Model::draw(u32 shader_program)
{
  for (int i=0; i < meshes.size(); i++)
  {
    meshes[i].draw(shader_program);
  }
}

void Model::load_model(std::string path)
{
  Assimp::Importer import;
  const aiScene *scene = import.ReadFile(path, aiProcess_Triangulate | aiProcess_FlipUVs);

  if (!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode)
  {
    printf("error loading model :%s\n", import.GetErrorString());
    return;
  }

  directory = path.substr(0, path.find_last_of('/'));
  process_node(scene->mRootNode, scene);
}

void Model::process_node(aiNode *node, const aiScene *scene)
{
  for (int i=0; i < node->mNumMeshes; i++)
  {
    aiMesh *mesh = scene->mMeshes[node->mMeshes[i]];
    meshes.push_back(process_mesh(mesh, scene));
  }

  for (int i=0; i<node->mNumChildren; i++)
  {
    process_node(node->mChildren[i], scene);
  }
}

Mesh Model::process_mesh(aiMesh *mesh, const aiScene *scene)
{
  std::vector<Vertex> vertices;
  std::vector<u32> indices;
  std::vector<Texture> textures;

  for (u32 i=0; i < mesh->mNumVertices; i++)
  {
    Vec3 position;
    position.x = mesh->mVertices[i].x;
    position.y = mesh->mVertices[i].y;
    position.z = mesh->mVertices[i].z;

    Vec3 normal;
    normal.x = mesh->mNormals[i].x;
    normal.y = mesh->mNormals[i].y;
    normal.z = mesh->mNormals[i].z;

    Vec2 texture = {0, 0};
    if (mesh->mTextureCoords[0])
    {
      texture.x = mesh->mTextureCoords[0][i].x;
      texture.y = mesh->mTextureCoords[0][i].y;
    }

    struct Vertex vertex;
    vertex.position = position;
    vertex.normal = normal;
    vertex.texture = texture;

    vertices.push_back(vertex);
  }
  // process indices
  for (u32 i = 0; i < mesh->mNumFaces; i++)
  {
    aiFace face = mesh->mFaces[i];
    for(u32 j = 0; j < face.mNumIndices; j++)
    {
      indices.push_back(face.mIndices[j]);
    }
  }
  // process material
  if (mesh->mMaterialIndex >= 0)
  {
    aiMaterial *material = scene->mMaterials[mesh->mMaterialIndex];
    std::vector<Texture> diffuse_maps = load_material_textures(material, aiTextureType_DIFFUSE, TextureDiffuse);
    textures.insert(textures.end(), diffuse_maps.begin(), diffuse_maps.end());
    std::vector<Texture> specular_maps = load_material_textures(material, aiTextureType_SPECULAR, TextureSpecular);
    textures.insert(textures.end(), specular_maps.begin(), specular_maps.end());
  }

  return Mesh(vertices, indices, textures);
}

std::vector<Texture> Model::load_material_textures(aiMaterial *mat, aiTextureType type, TextureType tex_type)
{
  std::vector<Texture> textures;
  for(u32 i=0; i<mat->GetTextureCount(type); i++)
  {
    bool load_texture = true;
    aiString str;
    mat->GetTexture(type, i, &str);
    const char* fname = str.C_Str();

    for (s32 j=0; j<loaded_textures.size();  j++)
    {
      if (std::strcmp(loaded_textures[j].fname.data(), fname) == 0)
      {
        load_texture = false;
        textures.push_back(loaded_textures[j]);
        break;
      }
    }
    if (load_texture)
    {
      Texture texture;
      texture.id = TextureFromFile(fname, directory);
      texture.type = tex_type;
      texture.fname = std::string(fname);
      textures.push_back(texture);
      loaded_textures.push_back(texture);
    }
  }

  return textures;
}

class Shader {
  // @note: this is a draft, I think frankly, it's a stupid idea to be making this at this point
  // but my goal is to look at my code at this stage (which is in the second half of (or so I think)
  // learnopengl and identify repeated code that I think I can yank out and can make convenient to write.
  // The precondition for all of this is that I do not remodel the program based off of some vague idea of
  // cleanliness in my head. This is all still very procedural, I just want to minimize the amount I type
  // and at the same time see how well I can identify good abstractions
  //
  //
  // I much prefer to have things be not a class, especially if I look at how I did my lovely
  // math functions, which are so simple and straightforward
  public:
    u32 id;
    
    // @note: all well and good until you get compute shaders
    // then the entire thing shits the bed
    Shader(char* vertex_shader_source, char* fragment_shader_source) {
      id = gl_shader_program(vertex_shader_source, fragment_shader_source);
    }

    void use() {
      glUseProgram(id);
    }

    void draw_triangles(u32 vao, u32 count) {
      glBindVertexArray(vao);
      glDrawArrays(GL_TRIANGLES, 0, count);
    }

    void set_1i(char* variable, s32 value) {
      s32 loc = glGetUniformLocation(id, variable);
      glUniform1i(loc, value);
    }

    void set_matrix4fv(char* variable, Mat4 value, int count) {
      s32 loc = glGetUniformLocation(id, variable);
      glUniformMatrix4fv(loc, count, GL_TRUE, value.buffer);
    };

    ~Shader() {
      // @note: this can literally be replaced by another function that goes over the entire list
      // of shader_programs near the program exit and deletes them, if I even need to do that.
      glDeleteProgram(id);
    }
};

int main(int argc, char* argv[])
{

  // ============ END ============
	int width = 1024;
	int height = 768;
    
	if (SDL_Init(SDL_INIT_VIDEO) != 0)
	{
		printf("Error initialising SDL2: %s\n", SDL_GetError());
		return 0;
	};
    
	// set opengl version and profile
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
  SDL_GL_SetAttribute( SDL_GL_STENCIL_SIZE, 8 );
    
	// initialise window with opengl flag
	SDL_Window* window = SDL_CreateWindow("SDL Test",
                                          50,
                                          50,
                                          width,
                                          height,
                                          SDL_WINDOW_OPENGL);
    
    SDL_SetRelativeMouseMode(SDL_TRUE);
   
	// create an opengl context
	SDL_GLContext context = SDL_GL_CreateContext(window);
	if (!context)
	{
		printf("OpenGL context creation failed: %s\n", SDL_GetError());
		return -1;
	}
    
    
	// load glad
	if (!gladLoadGLLoader((GLADloadproc)SDL_GL_GetProcAddress)) {
		printf("Failed to initialize Glad\n");
		return 1;
	}
    
  // filesystem playground stuff
  size_t read_count;
  char* vertex_source = (char*)SDL_LoadFile("./source/shaders/depth_test.vs.glsl", &read_count);
  char* fragment_source = (char*)SDL_LoadFile("./source/shaders/depth_test.fs.glsl", &read_count);
  char* blend_shader_source = (char*)SDL_LoadFile("./source/shaders/blend_test.fs.glsl", &read_count);
  char* fbo_vs = (char*)SDL_LoadFile("./source/shaders/fbo.vs.glsl", &read_count);
  char* fbo_fs = (char*)SDL_LoadFile("./source/shaders/fbo.fs.glsl", &read_count);
  char* cubemap_vs = (char*)SDL_LoadFile("./source/shaders/cubemap.vs.glsl", &read_count);
  char* cubemap_fs = (char*)SDL_LoadFile("./source/shaders/cubemap.fs.glsl", &read_count);
  char* refl_vs = (char*)SDL_LoadFile("./source/shaders/refl.vs.glsl", &read_count);
  char* refl_fs = (char*)SDL_LoadFile("./source/shaders/refl.fs.glsl", &read_count);
  char* refr_vs = (char*)SDL_LoadFile("./source/shaders/refr.vs.glsl", &read_count);
  char* refr_fs = (char*)SDL_LoadFile("./source/shaders/refr.fs.glsl", &read_count);
    
  u32 shader_program = gl_shader_program(vertex_source, fragment_source);
	u32 blend_shader_program = gl_shader_program(vertex_source, blend_shader_source);
	u32 fbo_shader_program = gl_shader_program(fbo_vs, fbo_fs);
  u32 cubemap_shader_program = gl_shader_program(cubemap_vs, cubemap_fs);
  u32 refl_shader_program = gl_shader_program(refl_vs, refl_fs);
  u32 refr_shader_program = gl_shader_program(refr_vs, refr_fs);

	printf("Successfully compiled shaders.\n");
    
  float cubeVertices[] = {
    // Back face
    -0.5f, -0.5f, -0.5f,  0.0f, 0.0f, // Bottom-left
     0.5f,  0.5f, -0.5f,  1.0f, 1.0f, // top-right
     0.5f, -0.5f, -0.5f,  1.0f, 0.0f, // bottom-right         
     0.5f,  0.5f, -0.5f,  1.0f, 1.0f, // top-right
    -0.5f, -0.5f, -0.5f,  0.0f, 0.0f, // bottom-left
    -0.5f,  0.5f, -0.5f,  0.0f, 1.0f, // top-left
    // Front face
    -0.5f, -0.5f,  0.5f,  0.0f, 0.0f, // bottom-left
     0.5f, -0.5f,  0.5f,  1.0f, 0.0f, // bottom-right
     0.5f,  0.5f,  0.5f,  1.0f, 1.0f, // top-right
     0.5f,  0.5f,  0.5f,  1.0f, 1.0f, // top-right
    -0.5f,  0.5f,  0.5f,  0.0f, 1.0f, // top-left
    -0.5f, -0.5f,  0.5f,  0.0f, 0.0f, // bottom-left
    // Left face
    -0.5f,  0.5f,  0.5f,  1.0f, 0.0f, // top-right
    -0.5f,  0.5f, -0.5f,  1.0f, 1.0f, // top-left
    -0.5f, -0.5f, -0.5f,  0.0f, 1.0f, // bottom-left
    -0.5f, -0.5f, -0.5f,  0.0f, 1.0f, // bottom-left
    -0.5f, -0.5f,  0.5f,  0.0f, 0.0f, // bottom-right
    -0.5f,  0.5f,  0.5f,  1.0f, 0.0f, // top-right
    // Right face
     0.5f,  0.5f,  0.5f,  1.0f, 0.0f, // top-left
     0.5f, -0.5f, -0.5f,  0.0f, 1.0f, // bottom-right
     0.5f,  0.5f, -0.5f,  1.0f, 1.0f, // top-right         
     0.5f, -0.5f, -0.5f,  0.0f, 1.0f, // bottom-right
     0.5f,  0.5f,  0.5f,  1.0f, 0.0f, // top-left
     0.5f, -0.5f,  0.5f,  0.0f, 0.0f, // bottom-left     
    // Bottom face
    -0.5f, -0.5f, -0.5f,  0.0f, 1.0f, // top-right
     0.5f, -0.5f, -0.5f,  1.0f, 1.0f, // top-left
     0.5f, -0.5f,  0.5f,  1.0f, 0.0f, // bottom-left
     0.5f, -0.5f,  0.5f,  1.0f, 0.0f, // bottom-left
    -0.5f, -0.5f,  0.5f,  0.0f, 0.0f, // bottom-right
    -0.5f, -0.5f, -0.5f,  0.0f, 1.0f, // top-right
    // Top face
    -0.5f,  0.5f, -0.5f,  0.0f, 1.0f, // top-left
     0.5f,  0.5f,  0.5f,  1.0f, 0.0f, // bottom-right
     0.5f,  0.5f, -0.5f,  1.0f, 1.0f, // top-right     
     0.5f,  0.5f,  0.5f,  1.0f, 0.0f, // bottom-right
    -0.5f,  0.5f, -0.5f,  0.0f, 1.0f, // top-left
    -0.5f,  0.5f,  0.5f,  0.0f, 0.0f  // bottom-left     
  };

   float planeVertices[] = {
      // positions          // texture Coords (note we set these higher than 1 (together with GL_REPEAT as texture wrapping mode). this will cause the floor texture to repeat)
      // BottomFace
      -5.0f, -1.0f, -5.0f,  0.0f, 2.0f, // top-right
       5.0f, -1.0f, -5.0f,  2.0f, 2.0f, // top-left
       5.0f, -1.0f,  5.0f,  2.0f, 0.0f, // bottom-left
       5.0f, -1.0f,  5.0f,  2.0f, 0.0f, // bottom-left
      -5.0f, -1.0f,  5.0f,  0.0f, 0.0f, // bottom-right
      -5.0f, -1.0f, -5.0f,  0.0f, 2.0f, // top-right
      // Top face
      -5.0f, -0.5f, -5.0f,  0.0f, 2.0f, // top-left
       5.0f, -0.5f,  5.0f,  2.0f, 0.0f, // bottom-right
       5.0f, -0.5f, -5.0f,  2.0f, 2.0f, // top-right     
       5.0f, -0.5f,  5.0f,  2.0f, 0.0f, // bottom-right
      -5.0f, -0.5f, -5.0f,  0.0f, 2.0f, // top-left
      -5.0f, -0.5f,  5.0f,  0.0f, 0.0f  // bottom-left     
    };

  float quadVertices[] = {
      // Front face
      -0.5f, -0.5f,  0.0f, 0.0f, // bottom-left
       0.5f, -0.5f,  1.0f, 0.0f, // bottom-right
       0.5f,  0.5f,  1.0f, 1.0f, // top-right
       0.5f,  0.5f,  1.0f, 1.0f, // top-right
      -0.5f,  0.5f,  0.0f, 1.0f, // top-left
      -0.5f, -0.5f,  0.0f, 0.0f, // bottom-left
      // Back face
      -0.5f, -0.5f,  0.0f, 0.0f, // Bottom-left
       0.5f,  0.5f,  1.0f, 1.0f, // top-right
       0.5f, -0.5f,  1.0f, 0.0f, // bottom-right         
       0.5f,  0.5f,  1.0f, 1.0f, // top-right
      -0.5f, -0.5f,  0.0f, 0.0f, // bottom-left
      -0.5f,  0.5f,  0.0f, 1.0f, // top-left
    };

  float fboVertices[] = {
      -1.0f, -1.0f,  0.0f, 0.0f, // bottom-left
       1.0f, -1.0f,  1.0f, 0.0f, // bottom-right
       1.0f,  1.0f,  1.0f, 1.0f, // top-right
       1.0f,  1.0f,  1.0f, 1.0f, // top-right
      -1.0f,  1.0f,  0.0f, 1.0f, // top-left
      -1.0f, -1.0f,  0.0f, 0.0f, // bottom-left
  };

  float skyboxVertices[] = {
    // positions          
    -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,

    -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,

     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,

    -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,

    -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,

    -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
  };
  float reflVertices[] = {
    // positions          // texture Coords (note we set these higher than 1 (together with GL_REPEAT as texture wrapping mode). this will cause the floor texture to repeat)
    // Top face
    //-5.0f,  0.5f, -5.0f,  0.0f, 1.0f, 0.0f,// top-left
    // 5.0f,  0.5f,  5.0f,  0.0f, 1.0f, 0.0f,// bottom-right
    // 5.0f,  0.5f, -5.0f,  0.0f, 1.0f, 0.0f,// top-right     
    // 5.0f,  0.5f,  5.0f,  0.0f, 1.0f, 0.0f,// bottom-right
    //-5.0f,  0.5f, -5.0f,  0.0f, 1.0f, 0.0f,// top-left
    //-5.0f,  0.5f,  5.0f,  0.0f, 1.0f, 0.0f,// bottom-left     
#if REFLECTIVE_PLANE
    // Back face
    -0.5f, -0.5f, -0.5f,  0.0f, 0.0f, -1.0f, // Bottom-left
     0.5f,  0.5f, -0.5f,  0.0f, 0.0f, -1.0f, // top-right
     0.5f, -0.5f, -0.5f,  0.0f, 0.0f, -1.0f, // bottom-right         
     0.5f,  0.5f, -0.5f,  0.0f, 0.0f, -1.0f, // top-right
    -0.5f, -0.5f, -0.5f,  0.0f, 0.0f, -1.0f, // bottom-left
    -0.5f,  0.5f, -0.5f,  0.0f, 0.0f, -1.0f, // top-left
    // Front face
    -0.5f, -0.5f,  0.5f,  0.0f, 0.0f, 1.0f, // bottom-left
     0.5f, -0.5f,  0.5f,  0.0f, 0.0f, 1.0f, // bottom-right
     0.5f,  0.5f,  0.5f,  0.0f, 0.0f, 1.0f, // top-right
     0.5f,  0.5f,  0.5f,  0.0f, 0.0f, 1.0f, // top-right
    -0.5f,  0.5f,  0.5f,  0.0f, 0.0f, 1.0f, // top-left
    -0.5f, -0.5f,  0.5f,  0.0f, 0.0f, 1.0f, // bottom-left
    // Left face
    -0.5f,  0.5f,  0.5f,  -1.0f, 0.0f, 0.0f, // top-right
    -0.5f,  0.5f, -0.5f,  -1.0f, 0.0f, 0.0f, // top-left
    -0.5f, -0.5f, -0.5f,  -1.0f, 0.0f, 0.0f, // bottom-left
    -0.5f, -0.5f, -0.5f,  -1.0f, 0.0f, 0.0f, // bottom-left
    -0.5f, -0.5f,  0.5f,  -1.0f, 0.0f, 0.0f, // bottom-right
    -0.5f,  0.5f,  0.5f,  -1.0f, 0.0f, 0.0f, // top-right
    // Right face
     0.5f,  0.5f,  0.5f,   1.0f, 0.0f, 0.0f, // top-left
     0.5f, -0.5f, -0.5f,   1.0f, 0.0f, 0.0f, // bottom-right
     0.5f,  0.5f, -0.5f,   1.0f, 0.0f, 0.0f, // top-right         
     0.5f, -0.5f, -0.5f,   1.0f, 0.0f, 0.0f, // bottom-right
     0.5f,  0.5f,  0.5f,   1.0f, 0.0f, 0.0f, // top-left
     0.5f, -0.5f,  0.5f,   1.0f, 0.0f, 0.0f, // bottom-left     
    // Bottom face
    -0.5f, -0.5f, -0.5f,  0.0f, -1.0f, 0.0f, // top-right
     0.5f, -0.5f, -0.5f,  0.0f, -1.0f, 0.0f, // top-left
     0.5f, -0.5f,  0.5f,  0.0f, -1.0f, 0.0f, // bottom-left
     0.5f, -0.5f,  0.5f,  0.0f, -1.0f, 0.0f, // bottom-left
    -0.5f, -0.5f,  0.5f,  0.0f, -1.0f, 0.0f, // bottom-right
    -0.5f, -0.5f, -0.5f,  0.0f, -1.0f, 0.0f, // top-right
#endif
    // Top face
    -4.0f,  0.0f, -4.0f,  0.0f,  1.0f, 0.0f, // top-left
     4.0f,  0.0f,  4.0f,  0.0f,  1.0f, 0.0f, // bottom-right
     4.0f,  0.0f, -4.0f,  0.0f,  1.0f, 0.0f, // top-right     
     4.0f,  0.0f,  4.0f,  0.0f,  1.0f, 0.0f, // bottom-right
    -4.0f,  0.0f, -4.0f,  0.0f,  1.0f, 0.0f, // top-left
    -4.0f,  0.0f,  4.0f,  0.0f,  1.0f, 0.0f  // bottom-left      
  };

  float refrVertices[] = {
    // Left face
    -0.5f,  0.5f,  0.5f,  -1.0f, 0.0f, 0.0f, // top-right
    -0.5f,  0.5f, -0.5f,  -1.0f, 0.0f, 0.0f, // top-left
    -0.5f, -0.5f, -0.5f,  -1.0f, 0.0f, 0.0f, // bottom-left
    -0.5f, -0.5f, -0.5f,  -1.0f, 0.0f, 0.0f, // bottom-left
    -0.5f, -0.5f,  0.5f,  -1.0f, 0.0f, 0.0f, // bottom-right
    -0.5f,  0.5f,  0.5f,  -1.0f, 0.0f, 0.0f, // top-right
    // Right face
    -0.5f,  0.5f,  0.5f,   1.0f, 0.0f, 0.0f, // top-left
    -0.5f, -0.5f, -0.5f,   1.0f, 0.0f, 0.0f, // bottom-right
    -0.5f,  0.5f, -0.5f,   1.0f, 0.0f, 0.0f, // top-right         
    -0.5f, -0.5f, -0.5f,   1.0f, 0.0f, 0.0f, // bottom-right
    -0.5f,  0.5f,  0.5f,   1.0f, 0.0f, 0.0f, // top-left
    -0.5f, -0.5f,  0.5f,   1.0f, 0.0f, 0.0f, // bottom-left     
  };

  stbi_set_flip_vertically_on_load(1);
  
	u32 cube_vao, cube_vbo, plane_vao, plane_vbo, quad_vao, quad_vbo, fbo_vao, fbo_vbo, 
      skybox_vao, skybox_vbo, refl_vao, refl_vbo, refr_vao, refr_vbo;
	
	glGenVertexArrays(1, &cube_vao);
	glGenBuffers(1, &cube_vbo);

	glBindVertexArray(cube_vao);
  glBindBuffer(GL_ARRAY_BUFFER, cube_vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(cubeVertices), &cubeVertices, GL_STATIC_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3*sizeof(float)));
  glBindVertexArray(0);

	glGenVertexArrays(1, &plane_vao);
	glGenBuffers(1, &plane_vbo);

	glBindVertexArray(plane_vao);
  glBindBuffer(GL_ARRAY_BUFFER, plane_vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(planeVertices), &planeVertices, GL_STATIC_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3*sizeof(float)));
  glBindVertexArray(0);

	glGenVertexArrays(1, &quad_vao);
	glGenBuffers(1, &quad_vbo);

	glBindVertexArray(quad_vao);
  glBindBuffer(GL_ARRAY_BUFFER, quad_vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), &quadVertices, GL_STATIC_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)0);
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)(2*sizeof(float)));
  glBindVertexArray(0);

  // framebuffer objects
	glGenVertexArrays(1, &fbo_vao);
	glGenBuffers(1, &fbo_vbo);

	glBindVertexArray(fbo_vao);
  glBindBuffer(GL_ARRAY_BUFFER, fbo_vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(fboVertices), &fboVertices, GL_STATIC_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)0);
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)(2*sizeof(float)));
  glBindVertexArray(0);

  // skybox objects
	glGenVertexArrays(1, &skybox_vao);
	glGenBuffers(1, &skybox_vbo);

	glBindVertexArray(skybox_vao);
  glBindBuffer(GL_ARRAY_BUFFER, skybox_vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxVertices), &skyboxVertices, GL_STATIC_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
  glBindVertexArray(0);

  // reflective surface objects
	glGenVertexArrays(1, &refl_vao);
	glGenBuffers(1, &refl_vbo);

	glBindVertexArray(refl_vao);
  glBindBuffer(GL_ARRAY_BUFFER, refl_vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(reflVertices), &reflVertices, GL_STATIC_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3*sizeof(float)));
  glBindVertexArray(0);

  // refractive surface objects
	glGenVertexArrays(1, &refr_vao);
	glGenBuffers(1, &refr_vbo);

	glBindVertexArray(refr_vao);
  glBindBuffer(GL_ARRAY_BUFFER, refr_vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(refrVertices), &refrVertices, GL_STATIC_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3*sizeof(float)));
  glBindVertexArray(0);

  // uniform buffer objects
  u32 ubo_camera_block;
  glGenBuffers(1, &ubo_camera_block);
  glBindBuffer(GL_UNIFORM_BUFFER, ubo_camera_block);
  glBufferData(GL_UNIFORM_BUFFER, 128, NULL, GL_STATIC_DRAW);
  glBindBuffer(GL_UNIFORM_BUFFER, 0);

  u32 window_tex_id;
  glGenTextures(1, &window_tex_id);
  glActiveTexture(GL_TEXTURE2);
  {
    char *path = "assets/window.png";
    s32 _width, _height, nrChannels;
    unsigned char *data = stbi_load(path, &_width, &_height, &nrChannels, 0);
    if (data)
    {
      GLenum format;
      if (nrChannels == 1)
        format = GL_RED;
      else if (nrChannels == 3)
        format = GL_RGB;
      else if (nrChannels == 4)
        format = GL_RGBA;

      glBindTexture(GL_TEXTURE_2D, window_tex_id);
      glTexImage2D(GL_TEXTURE_2D, 0, format, _width, _height, 0, format, GL_UNSIGNED_BYTE, data);
      glGenerateMipmap(GL_TEXTURE_2D);

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

      stbi_image_free(data);
    }
    else
    {
      printf("failed to load image texture at path: %s", path);
      stbi_image_free(data);
    }
  }

  u32 cube_tex_id;
  glGenTextures(1, &cube_tex_id);
  glActiveTexture(GL_TEXTURE0);
  gl_load_texture(cube_tex_id, "assets/container.jpg");

  u32 plane_tex_id;
  glGenTextures(1, &plane_tex_id);
  glActiveTexture(GL_TEXTURE1);
  gl_load_texture(plane_tex_id, "assets/smiling.png");

	// objects
	Vec3 model_translations[] = {
		Vec3{  0.5, 0.0,  0.0}, // 0: origin square
		Vec3{ -1.0, 0.0, -1.0}, // 1: plane
		Vec3{ -1.0, 0.0, -0.5}, // 2: window between squares
		Vec3{  0.0, 0.0,  3.0}, // 3: window infront of origin square
		Vec3{ -2.5, 0.0, -0.5}, // 4: square to the left
		Vec3{ -1.0, 0.0, -1.5}, // 5: random square behind window between squares
    Vec3{ -1.0, 0.0, -8.0}, // 6: reflective plane
    Vec3{ -1.0, 2.0, -8.0}, // 6: refractive "window"
	};
    
	r32 FOV = 90.0;
	r32 time_curr;
	r32 time_prev = SDL_GetTicks64() / 100.0;
	// camera stuff
	Vec3 camera_pos  = Vec3{ 0.0, 0.0, 10.0f};
	Vec3 preset_up_dir = Vec3{ 0.0, 1.0, 0.0 };
    
  r32 angle_yaw, angle_pitch, angle_roll;
  angle_pitch = (r32)To_Radian(0.0f);
  angle_yaw = (r32)-To_Radian(90.0f);
  
  Vec3 camera_look = camera_look_around(angle_pitch, angle_yaw);
  
  // @todo: remove this, I dont like this and think that this is unnecessary
  Vec3 camera_look_increment;
	r32 camera_speed = 0.5f;
    
	Mat4 view = camera_create4m(camera_pos, camera_look, preset_up_dir);
	
	Mat4 proj = perspective4m((r32)To_Radian(90.0), (r32)width / (r32)height, 0.1f, 100.0f);
  // needs this
  u32 proj_loc;
  glUseProgram(cubemap_shader_program);
	proj_loc = glGetUniformLocation(cubemap_shader_program, "Projection");
	glUniformMatrix4fv(proj_loc, 1, GL_TRUE, proj.buffer);

  glUseProgram(refl_shader_program);
	proj_loc = glGetUniformLocation(refl_shader_program, "Projection");
	glUniformMatrix4fv(proj_loc, 1, GL_TRUE, proj.buffer);

  glUseProgram(refr_shader_program);
	proj_loc = glGetUniformLocation(refr_shader_program, "Projection");
	glUniformMatrix4fv(proj_loc, 1, GL_TRUE, proj.buffer);

  u32 block_binding = 0;
  u32 matrices_ind;
  matrices_ind = glGetUniformBlockIndex(shader_program, "Matrices");
  glUniformBlockBinding(shader_program, matrices_ind, block_binding);
  matrices_ind = glGetUniformBlockIndex(blend_shader_program, "Matrices");
  glUniformBlockBinding(blend_shader_program, matrices_ind, block_binding);
  // or glBindBufferBase();
  glBindBufferRange(GL_UNIFORM_BUFFER, block_binding, ubo_camera_block, 0, 128); 

  Mat4 col_major_proj = to_col_major4m(proj);
  glBindBuffer(GL_UNIFORM_BUFFER, ubo_camera_block);
  glBufferSubData(GL_UNIFORM_BUFFER, 64, 64, col_major_proj.buffer);
  glBindBuffer(GL_UNIFORM_BUFFER, 0);
	
	glEnable(GL_DEPTH_TEST);
  glEnable(GL_BLEND);
  glEnable(GL_CULL_FACE);
  glDepthFunc(GL_LESS);
  glCullFace(GL_BACK);
  //glFrontFace(GL_CW); // front-faces are clock-wise, this will make the back-faces visible (since the arrays used were
                      // setup as counter-clockwise)
  u32 fbo;
  glGenFramebuffers(1, &fbo);
  glBindFramebuffer(GL_FRAMEBUFFER, fbo);

  // create a texture for the framebuffer to render data to
  u32 fbo_tex;
  glGenTextures(1, &fbo_tex);
  glActiveTexture(GL_TEXTURE3);
  glBindTexture(GL_TEXTURE_2D, fbo_tex);
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glBindTexture(GL_TEXTURE_2D, 0);

  u32 rbo;
  glGenRenderbuffers(1, &rbo);
  glBindRenderbuffer(GL_RENDERBUFFER, rbo);
  glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, width, height);
  glBindRenderbuffer(GL_RENDERBUFFER, 0);

  // attach to current bound framebuffer object
  glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fbo_tex, 0);
  glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, rbo);

  if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
    printf("Error! Framebuffer is not completely setup\n");
    return -1;
  }
  glBindFramebuffer(GL_FRAMEBUFFER, 0);

  // generate_cubemap
  const char *cm_face_right = "assets/skybox/right.jpg";
  const char *cm_face_left = "assets/skybox/left.jpg";
  const char *cm_face_top = "assets/skybox/top.jpg";
  const char *cm_face_bottom = "assets/skybox/bottom.jpg";
  const char *cm_face_back = "assets/skybox/back.jpg";
  const char *cm_face_front = "assets/skybox/front.jpg";

  u32 cm_tex_id;
  {
    stbi_set_flip_vertically_on_load(0);
    glGenTextures(1, &cm_tex_id);
    glBindTexture(GL_TEXTURE_CUBE_MAP, cm_tex_id);
    int cm_width, cm_height, cm_nrChannels;
    unsigned char *data;
    // right face
    data = stbi_load(cm_face_right, &cm_width, &cm_height, &cm_nrChannels, 0);
    glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + 0, 0, GL_RGB, cm_width, cm_height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    // left face
    data = stbi_load(cm_face_left, &cm_width, &cm_height, &cm_nrChannels, 0);
    glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + 1, 0, GL_RGB, cm_width, cm_height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    // top face
    data = stbi_load(cm_face_top, &cm_width, &cm_height, &cm_nrChannels, 0);
    glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + 2, 0, GL_RGB, cm_width, cm_height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    // bottom face
    data = stbi_load(cm_face_bottom, &cm_width, &cm_height, &cm_nrChannels, 0);
    glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + 3, 0, GL_RGB, cm_width, cm_height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    // back face
    data = stbi_load(cm_face_back, &cm_width, &cm_height, &cm_nrChannels, 0);
    glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + 4, 0, GL_RGB, cm_width, cm_height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    // front face
    data = stbi_load(cm_face_front, &cm_width, &cm_height, &cm_nrChannels, 0);
    glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + 5, 0, GL_RGB, cm_width, cm_height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);

    // texture filtering methods
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);

    glUseProgram(cubemap_shader_program);
    glActiveTexture(GL_TEXTURE0);
    s32 skybox_loc = glGetUniformLocation(cubemap_shader_program, "skybox");
    glUniform1i(skybox_loc, 0);
    stbi_set_flip_vertically_on_load(1);
  }

  {
    glUseProgram(refl_shader_program);
    s32 skybox_loc = glGetUniformLocation(refl_shader_program, "skybox");
    glUniform1i(skybox_loc, 0);
  }

  {
    glUseProgram(refr_shader_program);
    s32 skybox_loc = glGetUniformLocation(refr_shader_program, "skybox");
    glUniform1i(skybox_loc, 0);
  }

	u8 game_running = true;
    
  u8 hold_lshift = false;
	u8 move_w = false;
	u8 move_a = false;
	u8 move_s = false;
	u8 move_d = false;
    
	while(game_running)
	{
		
		// frame delta
		time_curr = SDL_GetTicks64() / 100.0;
		r32 time_delta = time_curr - time_prev;
		
		r32 camera_speed_adjusted = time_delta * camera_speed;
		camera_look_increment = scaler_multiply3v(camera_look, camera_speed_adjusted);
        
		SDL_Event ev;
		while(SDL_PollEvent(&ev))
		{
            
			// INPUT
			switch (ev.type)
			{
				case (SDL_QUIT):
				{
					game_running = false;
				} break;
				case (SDL_KEYDOWN):
				{
          if (ev.key.keysym.sym == SDLK_LSHIFT)
          {
              hold_lshift = true;
          }
					if (ev.key.keysym.sym == SDLK_w)
					{
						move_w = true;
					}
					if (ev.key.keysym.sym == SDLK_s)
					{
						move_s = true;
					}
					if (ev.key.keysym.sym == SDLK_a)
					{
						move_a = true;
					}
					if (ev.key.keysym.sym == SDLK_d)
					{
						move_d = true;
					}
				} break;
				case (SDL_KEYUP):
				{
          if (ev.key.keysym.sym == SDLK_LSHIFT)
          {
              hold_lshift = false;
          }
					if (ev.key.keysym.sym == SDLK_w)
					{
						move_w = false;
					}
					if (ev.key.keysym.sym == SDLK_s)
					{
						move_s = false;
					}
					if (ev.key.keysym.sym == SDLK_a)
					{
						move_a = false;
					}
					if (ev.key.keysym.sym == SDLK_d)
					{
						move_d = false;
					}
				} break;
        case (SDL_MOUSEMOTION):
        {
          SDL_MouseMotionEvent mouse_event = ev.motion;
          r32 x_motion = (r32)mouse_event.xrel;
          r32 y_motion = (r32)mouse_event.yrel;
					if (x_motion != 0.0 || y_motion != 0.0)
					{
						angle_yaw = angle_yaw + To_Radian(x_motion * 0.1f);
						angle_pitch = clampf(angle_pitch + To_Radian(-y_motion * 0.1f), To_Radian(-89.0f), To_Radian(89.0f));
						
						camera_look = camera_look_around(angle_pitch, angle_yaw);
					}
        } break;
				default:
				{
					break;
				}
			}
		}
        
		// PROCESS
		if (move_w)
		{
			camera_pos = add3v(camera_pos, camera_look_increment);
		}
		if (move_s)
		{
			camera_pos = subtract3v(camera_pos, camera_look_increment);
		}
		if (move_a)
		{
			Vec3 camera_right = normalize3v(cross_multiply3v(preset_up_dir, camera_look));
			Vec3 camera_right_scaled = scaler_multiply3v(camera_right, camera_speed_adjusted);
			camera_pos = add3v(camera_pos, camera_right_scaled);
		}
		if (move_d)
		{
			Vec3 camera_right = normalize3v(cross_multiply3v(preset_up_dir, camera_look));
			Vec3 camera_right_scaled = scaler_multiply3v(camera_right, camera_speed_adjusted);
			camera_pos = subtract3v(camera_pos, camera_right_scaled);
		}
    view = camera_create4m(camera_pos, add3v(camera_pos, camera_look), preset_up_dir);
        
		// object shader program stuff
    Mat4 col_major_view = to_col_major4m(view);
    glBindBuffer(GL_UNIFORM_BUFFER, ubo_camera_block);
    glBufferSubData(GL_UNIFORM_BUFFER, 0, 64, col_major_view.buffer);
    glBindBuffer(GL_UNIFORM_BUFFER, 0);
    
    u32 view_loc;
    glUseProgram(refl_shader_program);
    view_loc = glGetUniformLocation(refl_shader_program, "View");
		glUniformMatrix4fv(view_loc, 1, GL_TRUE, view.buffer);

    glUseProgram(refr_shader_program);
    view_loc = glGetUniformLocation(refr_shader_program, "View");
		glUniformMatrix4fv(view_loc, 1, GL_TRUE, view.buffer);

    glUseProgram(cubemap_shader_program);
    view_loc = glGetUniformLocation(cubemap_shader_program, "View");
    view.xyzw[0].w = 0.0f;
    view.xyzw[1].w = 0.0f;
    view.xyzw[2].w = 0.0f;
		glUniformMatrix4fv(view_loc, 1, GL_TRUE, view.buffer);

		time_prev = time_curr;
		
		// OUTPUT
    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
		glClearColor(1.0f, 0.6f, .6f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glEnable(GL_DEPTH_TEST);
    glDisable(GL_BLEND);
    { //plane
      glUseProgram(shader_program);
      // @note: this is just a test, I dont need to do this here;
      s32 tex_id_loc = glGetUniformLocation(shader_program, "TexId");
      glUniform1i(tex_id_loc, 1);
      Vec3 translation_iter = model_translations[1];
      Mat4 model = init_value4m(1.0);
      Mat4 model_translation = translation_matrix4m(translation_iter.x, translation_iter.y, translation_iter.z);
      model = multiply4m(model_translation, model);
      uint32_t model_loc = glGetUniformLocation(shader_program, "Model");
      glUniformMatrix4fv(model_loc, 1, GL_TRUE, model.buffer);
      glBindVertexArray(plane_vao);
      glBindTexture(GL_TEXTURE_2D, plane_tex_id);
      glDrawArrays(GL_TRIANGLES, 0, 12);
    }

    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    {//origin square
      glUseProgram(shader_program);
      glBindTexture(GL_TEXTURE_2D, cube_tex_id);
      s32 tex_id_loc = glGetUniformLocation(shader_program, "TexId");
      glUniform1i(tex_id_loc, 0);
      Vec3 translation_iter = model_translations[0];
      Mat4 model = init_value4m(1.0);
      Mat4 model_translation = translation_matrix4m(translation_iter.x, translation_iter.y, translation_iter.z);
      model = multiply4m(model_translation, model);
      uint32_t model_loc = glGetUniformLocation(shader_program, "Model");
      glUniformMatrix4fv(model_loc, 1, GL_TRUE, model.buffer);
      glBindVertexArray(cube_vao);
      glDrawArrays(GL_TRIANGLES, 0, 36);
    }
    {//square to the left
      glUseProgram(shader_program);
      glBindTexture(GL_TEXTURE_2D, cube_tex_id);
      s32 tex_id_loc = glGetUniformLocation(shader_program, "TexId");
      glUniform1i(tex_id_loc, 0);
      Vec3 translation_iter = model_translations[4];
      Mat4 model = init_value4m(1.0);
      Mat4 model_translation = translation_matrix4m(translation_iter.x, translation_iter.y, translation_iter.z);
      model = multiply4m(model_translation, model);
      uint32_t model_loc = glGetUniformLocation(shader_program, "Model");
      glUniformMatrix4fv(model_loc, 1, GL_TRUE, model.buffer);
      glBindVertexArray(cube_vao);
      glDrawArrays(GL_TRIANGLES, 0, 36);
    }
    {//random square behind window between squares
      glUseProgram(shader_program);
      s32 tex_id_loc = glGetUniformLocation(shader_program, "TexId");
      glUniform1i(tex_id_loc, 0);
      Vec3 translation_iter = model_translations[5];
      Mat4 model = init_value4m(1.0);
      Mat4 model_translation = translation_matrix4m(translation_iter.x, translation_iter.y, translation_iter.z);
      model = multiply4m(model_translation, model);
      uint32_t model_loc = glGetUniformLocation(shader_program, "Model");
      glUniformMatrix4fv(model_loc, 1, GL_TRUE, model.buffer);
      glBindVertexArray(cube_vao);
      glBindTexture(GL_TEXTURE_2D, cube_tex_id);
      glDrawArrays(GL_TRIANGLES, 0, 36);
    }
    { // reflective plane
      glUseProgram(refl_shader_program);
      Vec3 translation_iter = model_translations[6];
      Mat4 model = init_value4m(1.0);
      Mat4 model_translation = translation_matrix4m(translation_iter.x, translation_iter.y, translation_iter.z);

      model = multiply4m(model_translation, model);
      uint32_t model_loc = glGetUniformLocation(refl_shader_program, "Model");
      glUniformMatrix4fv(model_loc, 1, GL_TRUE, model.buffer);

      uint32_t camera_pos_loc = glGetUniformLocation(refl_shader_program, "cameraPos");
      glUniform3fv(camera_pos_loc, 1, camera_pos.data);
      glBindVertexArray(refl_vao);
      glDrawArrays(GL_TRIANGLES, 0, 6);
    }
    { // reflective plane
      glUseProgram(refr_shader_program);
      Vec3 translation_iter = model_translations[7];
      Mat4 model = init_value4m(1.0);
      Mat4 model_translation = translation_matrix4m(translation_iter.x, translation_iter.y, translation_iter.z);

      model = multiply4m(model_translation, model);
      uint32_t model_loc = glGetUniformLocation(refr_shader_program, "Model");
      glUniformMatrix4fv(model_loc, 1, GL_TRUE, model.buffer);

      uint32_t camera_pos_loc = glGetUniformLocation(refr_shader_program, "cameraPos");
      glUniform3fv(camera_pos_loc, 1, camera_pos.data);
      glBindVertexArray(refr_vao);
      glDrawArrays(GL_TRIANGLES, 0, 12);
    }
    {
      glDepthFunc(GL_LEQUAL);
      glUseProgram(cubemap_shader_program);
      glActiveTexture(GL_TEXTURE0);
      glBindVertexArray(skybox_vao);
      glBindTexture(GL_TEXTURE_CUBE_MAP, cm_tex_id);
      glDrawArrays(GL_TRIANGLES, 0, 36);
      glDepthFunc(GL_LESS);
    }

    // @note: this is to demonstrate the limitations of blending with the depth buffer.
    // Currently, this will show a weird behavior where since we render the transparent object
    // closest to the camera first, the second window, further from the player will be discarded by the 
    // depth buffer and will be invisible.
    // This is a limiation of transparent objects with the depth buffer. This does not happen with opaque objects.
    //
    // The "fix" if we can even call it that, is to render objects in order, furthest first and closest second, in layers.
    
    {//window infront of origin square
      glUseProgram(blend_shader_program);
      s32 tex_id_loc = glGetUniformLocation(blend_shader_program, "TexId");
      glUniform1i(tex_id_loc, 2);
      Vec3 translation_iter = model_translations[3];
      Mat4 model = init_value4m(1.0);
      Mat4 model_translation = translation_matrix4m(translation_iter.x, translation_iter.y, translation_iter.z);
      model = multiply4m(model_translation, model);
      uint32_t model_loc = glGetUniformLocation(blend_shader_program, "Model");
      glUniformMatrix4fv(model_loc, 1, GL_TRUE, model.buffer);
      glBindVertexArray(quad_vao);
      glBindTexture(GL_TEXTURE_2D, window_tex_id);
      glDrawArrays(GL_TRIANGLES, 0, 12);
    }
    {//window between squares
      glUseProgram(blend_shader_program);
      s32 tex_id_loc = glGetUniformLocation(blend_shader_program, "TexId");
      glUniform1i(tex_id_loc, 2);
      Vec3 translation_iter = model_translations[2];
      Mat4 model = init_value4m(1.0);
      Mat4 model_translation = translation_matrix4m(translation_iter.x, translation_iter.y, translation_iter.z);
      model = multiply4m(model_translation, model);
      uint32_t model_loc = glGetUniformLocation(blend_shader_program, "Model");
      glUniformMatrix4fv(model_loc, 1, GL_TRUE, model.buffer);
      glBindVertexArray(quad_vao);
      glBindTexture(GL_TEXTURE_2D, window_tex_id);
      glDrawArrays(GL_TRIANGLES, 0, 12);
    }
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    // draw everything to a framebuffer object
    glDisable(GL_DEPTH_TEST);
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f); 
    glClear(GL_COLOR_BUFFER_BIT);
    {
      glUseProgram(fbo_shader_program);
      glBindVertexArray(fbo_vao);
      // @note: this glActiveTexture call was the bane of my existence for the day, this is done to check this particular
      // thing regarding which texture unit the framebuffer object gets called to and it turns out, it needs a glActiveTexture
      // call (atleast in my case) since I am rendering multiple textures which are bound to different texture units,
      // primarily because of the different shaders I am using. 
      //
      // So this is why I need to call this, but what I could also do is call glActiveTexture when creating the texture 
      // and it would have the same effect as this
      glActiveTexture(GL_TEXTURE0);
      glBindTexture(GL_TEXTURE_2D, fbo_tex);
      s32 tex_id_loc = glGetUniformLocation(fbo_shader_program, "TexId");
      glUniform1i(tex_id_loc, 0);
      glDrawArrays(GL_TRIANGLES, 0, 6);
    }
    glEnable(GL_DEPTH_TEST);
		SDL_GL_SwapWindow(window);
	}
	
	// opengl free calls
	//glDeleteVertexArrays(1, &VAO);
	//glDeleteBuffers(1, &VBO);
	glDeleteProgram(shader_program);
	glDeleteProgram(blend_shader_program);
  glDeleteProgram(fbo_shader_program);
	
	// sdl free calls
	SDL_GL_DeleteContext(context);
	SDL_DestroyWindow(window);
	SDL_Quit();
	return 0;
}