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/* OpenGL example code - Indexed VBO
*
* same as the "Shader and VBO" example, only with an indexed vbo.
*
* Autor: Jakob Progsch
*/
#include <GLXW/glxw.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <string>
#include <vector>
// helper to check and display for shader compiler errors
bool check_shader_compile_status(GLuint obj) {
GLint status;
glGetShaderiv(obj, GL_COMPILE_STATUS, &status);
if(status == GL_FALSE) {
GLint length;
glGetShaderiv(obj, GL_INFO_LOG_LENGTH, &length);
std::vector<char> log(length);
glGetShaderInfoLog(obj, length, &length, &log[0]);
std::cerr << &log[0];
return false;
}
return true;
}
// helper to check and display for shader linker error
bool check_program_link_status(GLuint obj) {
GLint status;
glGetProgramiv(obj, GL_LINK_STATUS, &status);
if(status == GL_FALSE) {
GLint length;
glGetProgramiv(obj, GL_INFO_LOG_LENGTH, &length);
std::vector<char> log(length);
glGetProgramInfoLog(obj, length, &length, &log[0]);
std::cerr << &log[0];
return false;
}
return true;
}
int main() {
int width = 640;
int height = 480;
if(glfwInit() == GL_FALSE) {
std::cerr << "failed to init GLFW" << std::endl;
return 1;
}
// select opengl version
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
// create a window
GLFWwindow *window;
if((window = glfwCreateWindow(width, height, "02indexed_vbo", 0, 0)) == 0) {
std::cerr << "failed to open window" << std::endl;
glfwTerminate();
return 1;
}
glfwMakeContextCurrent(window);
if(glxwInit()) {
std::cerr << "failed to init GL3W" << std::endl;
glfwDestroyWindow(window);
glfwTerminate();
return 1;
}
// shader source code
std::string vertex_source =
"#version 330\n"
"layout(location = 0) in vec4 vposition;\n"
"layout(location = 1) in vec4 vcolor;\n"
"out vec4 fcolor;\n"
"void main() {\n"
" fcolor = vcolor;\n"
" gl_Position = vposition;\n"
"}\n";
std::string fragment_source =
"#version 330\n"
"in vec4 fcolor;\n"
"layout(location = 0) out vec4 FragColor;\n"
"void main() {\n"
" FragColor = fcolor;\n"
"}\n";
// program and shader handles
GLuint shader_program, vertex_shader, fragment_shader;
// we need these to properly pass the strings
const char *source;
int length;
// create and compiler vertex shader
vertex_shader = glCreateShader(GL_VERTEX_SHADER);
source = vertex_source.c_str();
length = vertex_source.size();
glShaderSource(vertex_shader, 1, &source, &length);
glCompileShader(vertex_shader);
if(!check_shader_compile_status(vertex_shader)) {
glfwDestroyWindow(window);
glfwTerminate();
return 1;
}
// create and compiler fragment shader
fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
source = fragment_source.c_str();
length = fragment_source.size();
glShaderSource(fragment_shader, 1, &source, &length);
glCompileShader(fragment_shader);
if(!check_shader_compile_status(fragment_shader)) {
glfwDestroyWindow(window);
glfwTerminate();
return 1;
}
// create program
shader_program = glCreateProgram();
// attach shaders
glAttachShader(shader_program, vertex_shader);
glAttachShader(shader_program, fragment_shader);
// link the program and check for errors
glLinkProgram(shader_program);
check_program_link_status(shader_program);
// vao and vbo handle
GLuint vao, vbo, ibo;
// generate and bind the vao
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
// generate and bind the vertex buffer object
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
// data for a fullscreen quad
GLfloat vertexData[] = {
// X Y Z R G B
1.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, // vertex 0
-1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, // vertex 1
1.0f,-1.0f, 0.0f, 0.0f, 0.0f, 1.0f, // vertex 2
-1.0f,-1.0f, 0.0f, 1.0f, 0.0f, 0.0f, // vertex 3
}; // 4 vertices with 6 components (floats) each
// fill with data
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat)*4*6, vertexData, GL_STATIC_DRAW);
// set up generic attrib pointers
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6*sizeof(GLfloat), (char*)0 + 0*sizeof(GLfloat));
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6*sizeof(GLfloat), (char*)0 + 3*sizeof(GLfloat));
// generate and bind the index buffer object
glGenBuffers(1, &ibo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);
GLuint indexData[] = {
0,1,2, // first triangle
2,1,3, // second triangle
};
// fill with data
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLuint)*2*3, indexData, GL_STATIC_DRAW);
while(!glfwWindowShouldClose(window)) {
glfwPollEvents();
// clear first
glClear(GL_COLOR_BUFFER_BIT);
// use the shader program
glUseProgram(shader_program);
// bind the vao
glBindVertexArray(vao);
// draw
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
// check for errors
GLenum error = glGetError();
if(error != GL_NO_ERROR) {
std::cerr << error << std::endl;
break;
}
// finally swap buffers
glfwSwapBuffers(window);
}
// delete the created objects
glDeleteVertexArrays(1, &vao);
glDeleteBuffers(1, &vbo);
glDeleteBuffers(1, &ibo);
glDetachShader(shader_program, vertex_shader);
glDetachShader(shader_program, fragment_shader);
glDeleteShader(vertex_shader);
glDeleteShader(fragment_shader);
glDeleteProgram(shader_program);
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}
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