GameOfLife/main.cc

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <random>
#include <thread>
#include <utility>
#include <vector>

#include "shaders.hpp"

#define X 250
#define Y 250
#define GRID_SIZE X *Y

GLuint compileShader(GLenum type, const char *src) {
  GLuint shader = glCreateShader(type);
  glShaderSource(shader, 1, &src, nullptr);
  glCompileShader(shader);
  int success;
  glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
  if (!success) {
    char infoLog[512];
    glGetShaderInfoLog(shader, 512, nullptr, infoLog);
    std::cerr << "ERROR::SHADER_COMPILATION_ERROR\n" << infoLog << std::endl;
  }
  return shader;
}

GLuint linkProgram(std::vector<GLuint> shaders) {
  GLuint program = glCreateProgram();
  for (auto s : shaders)
    glAttachShader(program, s);
  glLinkProgram(program);
  int success;
  glGetProgramiv(program, GL_LINK_STATUS, &success);
  if (!success) {
    char infoLog[512];
    glGetProgramInfoLog(program, 512, nullptr, infoLog);
    std::cerr << "ERROR::PROGRAM_LINK_ERROR\n" << infoLog << std::endl;
  }
  for (auto s : shaders)
    glDeleteShader(s);
  return program;
}

void resizeCall(GLFWwindow *window, int width, int height) {
  glViewport(0, 0, width, height);
}

int main() {
  if (!glfwInit())
    return -1;

  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);

  GLFWwindow *w = glfwCreateWindow(800, 600, "game of life", NULL, NULL);
  if (!w)
    return -2;

  glfwMakeContextCurrent(w);

  if (glewInit() != GLEW_OK)
    return -3;

  glfwShowWindow(w);
  glViewport(0, 0, 800, 600);
  glfwSetFramebufferSizeCallback(w, resizeCall);

  /*gen tex*/
  GLuint tex[2];
  glGenTextures(2, tex);
  for (int i = 0; i < 2; ++i) {
    glBindTexture(GL_TEXTURE_2D, tex[i]);
    glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, X, Y);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
  }

  /*rnd noise*/
  std::vector<GLubyte> data(GRID_SIZE * 4);
  std::mt19937 rng;
  std::uniform_int_distribution<int> dist(0, 1);
  for (int i = 0; i < GRID_SIZE; ++i) {
    GLubyte v = dist(rng) * 255;
    data[i * 4 + 0] = v;   // R channel
    data[i * 4 + 1] = v;   // G channel
    data[i * 4 + 2] = v;   // B channel
    data[i * 4 + 3] = 255; // A channel
  }

  glBindTexture(GL_TEXTURE_2D, tex[0]);
  glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, X, Y, GL_RGBA, GL_UNSIGNED_BYTE,
                  data.data());

  GLuint cmp, rnd, vs, fs;
  cmp = linkProgram({compileShader(GL_COMPUTE_SHADER, computeShaderSrc)});

  vs = compileShader(GL_VERTEX_SHADER, vertexShaderSrc);
  fs = compileShader(GL_FRAGMENT_SHADER, fragmentShaderSrc);
  rnd = linkProgram({vs, fs});

  /*vtex*/
  GLuint VAO, VBO, EBO;
  glGenVertexArrays(1, &VAO);
  glBindVertexArray(VAO);

  glGenBuffers(1, &VBO);
  glGenBuffers(1, &EBO);

  glBindBuffer(GL_ARRAY_BUFFER, VBO);
  glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), quadVertices,
               GL_STATIC_DRAW);

  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(quadIndices), quadIndices,
               GL_STATIC_DRAW);

  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
  glEnableVertexAttribArray(0);

  glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
  glEnableVertexAttribArray(1);

  /**/
  int ri, wi;
  ri = 0;
  wi = 1;
  while (!glfwWindowShouldClose(w)) {
    glfwPollEvents();
    glClearColor(1.0, 0.0, 0.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);

    /*compute*/
    glUseProgram(cmp);
    glBindImageTexture(0, tex[wi], 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_RGBA8);
    glUniform1i(glGetUniformLocation(cmp, "srcTex"), 0);
    glUniform1i(glGetUniformLocation(cmp, "X"), X);
    glUniform1i(glGetUniformLocation(cmp, "Y"), Y);
    glDispatchCompute(X, Y, 1);
    glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);

    /*draw*/
    glUseProgram(rnd);
    glActiveTexture(GL_TEXTURE0);
    glUniform1i(glGetUniformLocation(rnd, "tex0"), 0);

    glBindVertexArray(VAO);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, (void *)0);
    std::this_thread::sleep_for(std::chrono::duration<double>(.05));

    glfwSwapBuffers(w);
    std::swap(ri, wi);
  }

  glfwTerminate();
  return 0;
}