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#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
void on_resize(GLFWwindow *win, int width, int height) {
glViewport(0, 0, width, height);
}
void get_max_attrib_count(int *attrib_count) {
glGetIntegerv(GL_MAX_VERTEX_ATTRIBS, attrib_count);
printf("Max vertex attribs %d\n", *attrib_count);
}
int main() {
// Initialize GLFW
if (!glfwInit()) {
return -1;
}
// Set the required options for GLFW
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
GLFWwindow *window = glfwCreateWindow(320, 240, "Blue screen", NULL, NULL);
if (!window) {
glfwTerminate();
return -1;
}
glfwSetFramebufferSizeCallback(window, (void *)on_resize);
glfwMakeContextCurrent(window);
// Initialize GLEW
GLenum glewStatus = glewInit();
if (glewStatus != GLEW_OK) {
printf("Failed to initialize GLEW: %s\n", glewGetErrorString(glewStatus));
return -1;
}
int attrib_count;
get_max_attrib_count(&attrib_count);
float vertices[] = {
0.5f, 0.5f, 0.0f, // top right
0.5f, -0.5f, 0.0f, // bottom right
-0.5f, -0.5f, 0.0f, // bottom left
-0.5f, 0.5f, 0.0f // top left
};
unsigned int indices[] = {
0, 1, 3, // first triangle
1, 2, 3 // second triangle
};
unsigned int VBO;
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 6 * 3, vertices,
GL_STATIC_DRAW);
const char *vertex_shader_src =
"#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"out vec4 vertexColor;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
" vertexColor = vec4(0.5, 0.0, 0.0, 1.0);\n"
"}\0";
unsigned int vertex_shader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertex_shader, 1, &vertex_shader_src, 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("ERROR::SHADER::VERTEX::COMPILATION_FAILED\n%s\n", info_log);
}
const char *fragment_shader_src = "#version 330 core\n"
"out vec4 FragColor;\n"
"uniform vec4 ourColor;\n"
"void main()\n"
"{\n"
" FragColor = ourColor;\n"
"}\0";
unsigned int fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragment_shader, 1, &fragment_shader_src, NULL);
glCompileShader(fragment_shader);
glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success);
if (!success) {
glGetShaderInfoLog(fragment_shader, 512, NULL, info_log);
printf("ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n%s\n", info_log);
}
unsigned int shader_program = glCreateProgram();
glAttachShader(shader_program, vertex_shader);
glAttachShader(shader_program, fragment_shader);
glLinkProgram(shader_program);
glGetProgramiv(shader_program, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shader_program, 512, NULL, info_log);
printf("ERROR::SHADER::PROGRAM::LINK_FAILED\n%s\n", info_log);
}
glDeleteShader(vertex_shader);
glDeleteShader(fragment_shader);
unsigned int VAO;
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
unsigned int EBO;
glGenBuffers(1, &EBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(float) * 2 * 3, indices,
GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
glEnableVertexAttribArray(0);
while (!glfwWindowShouldClose(window)) {
glClearColor(0.1f, 0.1f, 0.25f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shader_program);
float time_value = glfwGetTime();
float green_value = (sin(time_value) / 2.0f) + 0.5f;
int vertex_color_location =
glGetUniformLocation(shader_program, "ourColor");
glUniform4f(vertex_color_location, 0.0f, green_value, 0.0f, 1.0f);
glBindVertexArray(VAO);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glBindVertexArray(0);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 0;
}
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