cpp-game-engine/graphics/src/opengl_renderer.cxx

//
//  opengl_renderer.cxx
//  graphics
//
//  Created by Sam Jaffe on 5/20/19.
//  Copyright © 2019 Sam Jaffe. All rights reserved.
//

#include "renderer_impl.hpp"

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

#include "game/graphics/material.hpp"
#include "game/graphics/vertex.h"
#include "matrix/matrix.hpp"
#include "matrix/matrix_helpers.hpp"

using namespace graphics;

class opengl_renderer : public renderer_impl {
public:
  opengl_renderer();
  ~opengl_renderer();

  void draw(flyweight<material>, math::matr4 const &,
            std::vector<vertex> const &) override;
  void clear() override;
  void flush() override;

private:
  const math::matr4 identity{math::matrix::identity<float, 4>()};
  math::matr4 world_to_clip{identity};
  double current_time{0.0};
  unsigned int vertex_array_object{0}, vertex_buffer_object{0};
};

opengl_renderer::opengl_renderer() {
  glGenVertexArrays(1, &vertex_array_object);
  glBindVertexArray(vertex_array_object);
  glGenBuffers(1, &vertex_buffer_object);
  glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_object);
}

opengl_renderer::~opengl_renderer() {
  glDeleteBuffers(1, &vertex_buffer_object);
  glDeleteVertexArrays(1, &vertex_array_object);
}

void opengl_renderer::clear() {
  world_to_clip = identity;

  // vec2i resolution = env::resolution();
  // orthogonal_view(0.0, resolution[0], 0.0, resolution[1], -1.0, 1.0);

  glClearDepth(1.f);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glClearColor(0.f, 0.f, 0.0f, 1.f);
  glEnable(GL_DEPTH_TEST);

  // TODO: Use a unified time calculation
  current_time = time(NULL);

  // TODO: ???
  // scale(0.5, 0.5, 1); // Don't know why I need to do this
}

void opengl_renderer::flush() { glFlush(); }

void opengl_renderer::draw(flyweight<material> material,
                           math::matr4 const & object_to_world,
                           std::vector<vertex> const & vertices) {
  // TODO: Don't activate here?
  auto const & mat = material.actual();
  // TODO: Attatch shader-id to material-id
  unsigned int const id = mat.shaders.id;
  mat.activate();

  int objectLocation = glGetUniformLocation(id, "u_objectToWorldMatrix");
  glUniformMatrix4fv(objectLocation, 1, false, &object_to_world(0, 0));

  int clipLocation = glGetUniformLocation(id, "u_worldToClipMatrix");
  glUniformMatrix4fv(clipLocation, 1, false, &world_to_clip(0, 0));

  int timeLocation = glGetUniformLocation(id, "u_time");
  glUniform1d(timeLocation, current_time);

  // TODO: Cache attribute locations
  int positionLocation = glGetAttribLocation(id, "a_position");
  int colorLocation = glGetAttribLocation(id, "a_color");
  int texCoordsLocation = glGetAttribLocation(id, "a_texCoords");

  glEnableVertexAttribArray(positionLocation);
  glEnableVertexAttribArray(colorLocation);
  glEnableVertexAttribArray(texCoordsLocation);

  glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, sizeof(vertex),
                        &vertices[0].position);
  glVertexAttribPointer(colorLocation, 4, GL_UNSIGNED_BYTE, GL_TRUE,
                        sizeof(vertex), &vertices[0].color);
  glVertexAttribPointer(texCoordsLocation, 2, GL_FLOAT, GL_FALSE,
                        sizeof(vertex), &vertices[0].texture_coords);

  glDrawArrays(GL_TRIANGLES, 0, static_cast<GLsizei>(vertices.size()));

  glDisableVertexAttribArray(positionLocation);
  glDisableVertexAttribArray(colorLocation);
  glDisableVertexAttribArray(texCoordsLocation);
}

template <> renderer_impl * graphics::get_renderer_impl<driver::openGL>() {
  static opengl_renderer impl;
  return &impl;
}