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#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <vector>
#include <iostream>
#include <random>
#include <chrono>
#include "shader/vertex.glsl"
#include "shader/fragment.glsl"
#include "shader/compute.glsl"
const std::size_t particle_count = 100000;
GLint getUniform(GLuint program, const std::string& name) {
const GLint uniform = glGetUniformLocation(program, name.c_str());
if ( uniform == -1 ) {
std::cerr << "Could not bind uniform " << name << std::endl;
}
return uniform;
}
GLint compileShader(const std::string& source, GLenum type) {
GLint shader = glCreateShader(type);
if ( !shader ) {
std::cerr << "Cannot create a shader of type " << type << std::endl;
exit(-1);
}
const char* source_data = source.c_str();
const int source_length = source.size();
glShaderSource(shader, 1, &source_data, &source_length);
glCompileShader(shader);
GLint compiled;
glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
if ( !compiled ) {
std::cerr << "Cannot compile shader" << std::endl;
GLint maxLength = 0;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &maxLength);
std::vector<GLchar> errorLog(maxLength);
glGetShaderInfoLog(shader, maxLength, &maxLength, &errorLog[0]);
for( auto c : errorLog ) {
std::cerr << c;
}
std::cerr << std::endl;
}
return shader;
}
GLint setupShader() {
GLint shader = glCreateProgram();
glAttachShader(shader, compileShader(VERTEX_SHADER_CODE, GL_VERTEX_SHADER));
glAttachShader(shader, compileShader(FRAGMENT_SHADER_CODE, GL_FRAGMENT_SHADER));
glLinkProgram(shader);
return shader;
}
GLint setupComputeShader() {
GLint shader = glCreateProgram();
glAttachShader(shader, compileShader(COMPUTE_SHADER_CODE, GL_COMPUTE_SHADER));
glLinkProgram(shader);
return shader;
}
int window_width = 800;
int window_height = 600;
float world_width, world_height;
glm::mat4 MVP;
void updateMVP() {
world_width = 20.f;
world_height = world_width / window_width * window_height;
glm::mat4 projection = glm::ortho(
-(world_width /2), world_width/2,
-(world_height/2), world_height/2,
0.1f, 100.0f
);
glm::mat4 view = glm::lookAt(
glm::vec3(0,0,20),
glm::vec3(0,0,0),
glm::vec3(0,1,0)
);
glm::mat4 model = glm::mat4(1.0f);
MVP = projection * view * model;
}
void window_size_callback(GLFWwindow*, int width, int height) {
window_width = width;
window_height = height;
glViewport(0, 0, width, height);
updateMVP();
}
std::vector<GLfloat> makeInitialParticles(std::size_t count) {
std::vector<GLfloat> buffer;
buffer.reserve(3*count);
std::random_device rd;
std::mt19937 gen(rd());
std::uniform_real_distribution<GLfloat> distX(-world_width/2., world_width/2.);
std::uniform_real_distribution<GLfloat> distY(-world_height/2., world_height/2.);
std::uniform_real_distribution<GLfloat> distAge(0., 5.);
for ( std::size_t i = 0; i < count; ++i ) {
buffer.emplace_back(distX(gen));
buffer.emplace_back(distY(gen));
buffer.emplace_back(distAge(gen));
}
return buffer;
}
int main() {
if( !glfwInit() ) {
std::cerr << "Failed to initialize GLFW" << std::endl;
return -1;
}
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
GLFWwindow* const window = glfwCreateWindow(window_width, window_height, "computicle", NULL, NULL);
if( window == nullptr ){
std::cerr << "Failed to open GLFW window." << std::endl;
glfwTerminate();
return -1;
}
glfwSetWindowSizeCallback(window, window_size_callback);
glfwMakeContextCurrent(window);
if ( glewInit() != GLEW_OK ) {
std::cerr << "Failed to initialize GLEW" << std::endl;
glfwTerminate();
return -1;
}
glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
updateMVP();
GLint ShaderID = setupShader();
GLuint MatrixID = glGetUniformLocation(ShaderID, "MVP");
GLint ComputeShaderID = setupComputeShader();
GLuint WorldID = glGetUniformLocation(ComputeShaderID, "world");
auto vertex_buffer_data = makeInitialParticles(particle_count);
GLuint VertexArrayID;
glGenVertexArrays(1, &VertexArrayID);
glBindVertexArray(VertexArrayID);
glEnableVertexAttribArray(0);
GLuint VertexBufferID;
glGenBuffers(1, &VertexBufferID);
glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, VertexBufferID);
glBufferData(
GL_SHADER_STORAGE_BUFFER,
vertex_buffer_data.size() * sizeof(GLfloat),
vertex_buffer_data.data(),
GL_STATIC_DRAW
);
auto lastFrame = std::chrono::high_resolution_clock::now();
do {
// update particles at most 50 times per second
if ( std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::now() - lastFrame).count() >= 20 ) {
glUseProgram(ComputeShaderID);
glUniform2f(WorldID, world_width, world_height);
glDispatchCompute(particle_count, 1, 1);
glUseProgram(0);
lastFrame = std::chrono::high_resolution_clock::now();
}
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(ShaderID);
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
glBindBuffer(GL_ARRAY_BUFFER, VertexBufferID);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
glDrawArrays(GL_POINTS, 0, 3*particle_count);
glUseProgram(0);
glfwSwapBuffers(window);
glfwPollEvents();
}
while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
glfwWindowShouldClose(window) == 0 );
glDeleteBuffers(1, &VertexBufferID);
glDisableVertexAttribArray(0);
glDeleteVertexArrays(1, &VertexArrayID);
glDeleteProgram(ShaderID);
glDeleteProgram(ComputeShaderID);
glfwTerminate();
return 0;
}
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