cpp-game-engine/graphics/src/openGL/opengl_manager.cxx

//
//  helper.cxx
//  graphics
//
//  Created by Sam Jaffe on 5/18/19.
//  Copyright © 2019 Sam Jaffe. All rights reserved.
//

#include "helper.hpp"
#include "opengl_renderer.h"

#include <iostream>
#include <memory>
#include <sstream>
#ifdef __APPLE__
#include <OpenGL/gl3.h>
#endif

#include "scope_guard/scope_guard.hpp"
#include "vector/vector.hpp"

#include "game/graphics/exception.h"
#include "game/graphics/material.hpp"
#include "game/graphics/shader.hpp"
#include "game/graphics/shader_program.hpp"
#include "game/graphics/texture.hpp"
#include "game/util/env.hpp"
#include "game/util/files.hpp"
#include "game/util/time.hpp"

namespace graphics {
  extern void print_shader_error(GLuint, std::string const &);
  extern void print_shader_program_error(GLuint, std::string const &,
                                         std::string const &);

  struct compilation_error : std::runtime_error {
    using std::runtime_error::runtime_error;
  };

  struct linker_error : std::runtime_error {
    using std::runtime_error::runtime_error;
  };
}

using namespace graphics;

namespace {
  int glfmt(textures::format color_fmt) {
    switch (color_fmt) {
    case textures::format::RGB:
      return GL_RGB;
    case textures::format::RGBA:
      return GL_RGBA;
    }
  }

  int gltype(shaders::type tp) {
    switch (tp) {
    case shaders::type::FRAGMENT:
      return GL_FRAGMENT_SHADER;
    case shaders::type::VERTEX:
      return GL_VERTEX_SHADER;
    }
  }
}

texture opengl_manager::compile(textures::format color, math::vec2i size,
                                void const * buffer) const {
  //  textures::external_data data(env::resource_file(path));
  //  unsigned int init(format color_fmt, math::vec2i dimension,
  //                    void const * data) {
  unsigned int id;
  // Enable texturings
  //    glEnable( GL_TEXTURE_2D );

  // Tell OpenGL that our pixel data is single-byte aligned
  glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

  // Ask OpenGL for an unused texName (ID number) to use for this texture
  glGenTextures(1, &id);

  // Tell OpenGL to bind (set) this as the currently active texture
  glBindTexture(GL_TEXTURE_2D, id);
  // Set texture clamp vs. wrap (repeat)

  // one of: GL_CLAMP_TO_EDGE, GL_REPEAT, GL_MIRRORED_REPEAT,
  // GL_MIRROR_CLAMP_TO_EDGE, ...
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

  // the format our source pixel data is currently in; any of: GL_RGB,
  // GL_RGBA, GL_LUMINANCE, GL_LUMINANCE_ALPHA, ...
  int bufferFormat = glfmt(color);

  // the format we want the texture to me on the card; allows us to translate
  // into a different texture format as we upload to OpenGL
  int internalFormat = bufferFormat;

  /* glTexImage2D: Load a 2d texture image
   * target: Creating this as a 2d texture.
   * level: Which mipmap level to use as the "root" (0 = the highest-quality,
   *  full-res image), if mipmaps are enabled.
   * internalFormat: Type of texel format we want OpenGL to use for this
   *  texture internally on the video card.
   * width: Texel-width of image; for maximum compatibility, use 2^N + 2^B,
   *  where N is some integer in the range [3,10], and B is the border
   *  thickness [0,1]
   * height: Texel-height of image; for maximum compatibility, use 2^M + 2^B,
   *  where M is some integer in the range [3,10], and B is the border
   *  thickness [0,1]
   * border: Border size, in texels (must be 0 or 1)
   * format: Pixel format describing the composition of the pixel data in
   *  buffer
   * type: Pixel color components are unsigned bytes (one byte per color/alpha
   *  channel)
   * pixels: Location of the actual pixel data bytes/buffer
   */
  glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, size.x(), size.y(), 0,
               bufferFormat, GL_UNSIGNED_BYTE, buffer);

  glGenerateMipmap(GL_TEXTURE_2D);

  // Set magnification (texel > pixel) and minification (texel < pixel)
  // filters one of: GL_NEAREST, GL_LINEAR
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  // one of: GL_NEAREST, GL_LINEAR, GL_NEAREST_MIPMAP_NEAREST,
  // GL_NEAREST_MIPMAP_LINEAR, GL_LINEAR_MIPMAP_NEAREST,
  // GL_LINEAR_MIPMAP_LINEAR
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                  GL_NEAREST_MIPMAP_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 5);

  return texture{id, size};
}

shader opengl_manager::compile(shaders::type tp,
                               std::string const & path) const {
  std::unique_ptr<char const[]> buffer;

  // 1. Load the vertex shader code (text file) to a new memory buffer
  std::string const abs_path = env::resource_file(path);
  if (!(buffer = files::load(abs_path))) {
    throw file_read_error("shader", abs_path);
  }

  // 2. Create a new shader ID
  // GL_VERTEX_SHADER or GL_FRAGMENT_SHADER
  unsigned int id = glCreateShader(gltype(tp));

  // 3. Associate the shader code with the new shader ID
  char const * buffer_ptr = buffer.get();
  glShaderSource(id, 1, &buffer_ptr, NULL);

  // 4. Compile the shader (the shader compiler is built in to your graphics
  //    card driver)
  glCompileShader(id);

  // 5. Check for compile errors
  int return_code;
  glGetShaderiv(id, GL_COMPILE_STATUS, &return_code);

  if (return_code != GL_TRUE) {
    print_shader_error(id, abs_path);
    throw compilation_error("Could not compile the shader file");
  }

  return shader{id, tp, path};
}

shader_program opengl_manager::compile(identity<shader> fragmentShader,
                                       identity<shader> vertexShader) const {
  // 9. Create a new shader program ID
  unsigned int id = glCreateProgram();

  // 10. Attach the vertex and fragment shaders to the new shader program
  glAttachShader(id, vertexShader.id);
  glAttachShader(id, fragmentShader.id);

  // 11. Do some other advanced stuff we'll do later on (like setting generic
  // vertex attrib locations)
  glBindAttribLocation(id, 0, "a_position");
  glBindAttribLocation(id, 1, "a_color");
  glBindAttribLocation(id, 2, "a_texCoords");
  glBindAttribLocation(id, 3, "a_normal");

  // 12. Link the program
  glLinkProgram(id);

  // 13. Check for link errors
  int return_code;
  glGetProgramiv(id, GL_LINK_STATUS, &return_code);

  if (return_code != GL_TRUE) {
    //      print_shader_program_error(id, fragmentShader.actual().path,
    //                                 vertexShader.actual().path);
    throw linker_error("Could not link shader program");
  }
  return shader_program{id, fragmentShader, vertexShader};
}

opengl_uniform_data & opengl_manager::data(identity<shader_program> program) {
  auto & data = data_[program];
  // TODO: perform this in compile()
  if (data.uniform_id.empty()) {
    glUseProgram(program.id);
    using materials::uniform;
    data.uniform_id = {
        {uniform::NORMAL, glGetUniformLocation(program.id, "u_normalMap")},
        {uniform::DIFFUSE, glGetUniformLocation(program.id, "u_diffuseMap")},
        {uniform::SPECULAR, glGetUniformLocation(program.id, "u_specularMap")}};
  }
  return data;
}