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foo.cpp
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foo.cpp
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// Headers
#include <GL/glew.h>
#include <GL/glfw.h>
#include <iostream>
// Shader sources
const char* vertexSource =
"#version 150\n"
"in vec2 position;"
"in vec3 color;"
"out vec3 Color;"
"void main() {"
" Color = color;"
" gl_Position = vec4( position, 0.0, 1.0 );"
"}";
const char* fragmentSource =
"#version 150\n"
"in vec3 Color;"
"out vec4 outColor;"
"void main() {"
" outColor = vec4( Color, 1.0 );"
"}";
int main()
{
glfwInit();
glfwOpenWindowHint( GLFW_OPENGL_VERSION_MAJOR, 3 );
glfwOpenWindowHint( GLFW_OPENGL_VERSION_MINOR, 2 );
glfwOpenWindowHint( GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE );
glfwOpenWindowHint( GLFW_WINDOW_NO_RESIZE, GL_TRUE );
glfwOpenWindow( 800, 600, 0, 0, 0, 0, 0, 0, GLFW_WINDOW );
glfwSetWindowTitle( "OpenGL" );
// Initialize GLEW
glewExperimental = GL_TRUE;
glewInit();
// Create Vertex Array Object
GLuint vao;
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
// Create a Vertex Buffer Object and copy the vertex data to it
GLuint vbo;
glGenBuffers( 1, &vbo );
float vertices[] = {
-0.5f, 0.5f, 1.0f, 0.0f, 0.0f, // Top-left
0.5f, 0.5f, 0.0f, 1.0f, 0.0f, // Top-right
0.5f, -0.5f, 0.0f, 0.0f, 1.0f, // Bottom-right
-0.5f, -0.5f, 1.0f, 1.0f, 1.0f // Bottom-left
};
glBindBuffer( GL_ARRAY_BUFFER, vbo );
glBufferData( GL_ARRAY_BUFFER, sizeof( vertices ), vertices, GL_STATIC_DRAW );
// Create an element array
GLuint ebo;
glGenBuffers( 1, &ebo );
GLuint elements[] = {
0, 1, 2,
2, 3, 0
};
glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, ebo );
glBufferData( GL_ELEMENT_ARRAY_BUFFER, sizeof( elements ), elements, GL_STATIC_DRAW );
// Create and compile the vertex shader
GLuint vertexShader = glCreateShader( GL_VERTEX_SHADER );
glShaderSource( vertexShader, 1, &vertexSource, NULL );
glCompileShader( vertexShader );
// Create and compile the fragment shader
GLuint fragmentShader = glCreateShader( GL_FRAGMENT_SHADER );
glShaderSource( fragmentShader, 1, &fragmentSource, NULL );
glCompileShader( fragmentShader );
// Link the vertex and fragment shader into a shader program
GLuint shaderProgram = glCreateProgram();
glAttachShader( shaderProgram, vertexShader );
glAttachShader( shaderProgram, fragmentShader );
glBindFragDataLocation( shaderProgram, 0, "outColor" );
glLinkProgram( shaderProgram );
glUseProgram( shaderProgram );
// Specify the layout of the vertex data
GLint posAttrib = glGetAttribLocation( shaderProgram, "position" );
glEnableVertexAttribArray( posAttrib );
glVertexAttribPointer( posAttrib, 2, GL_FLOAT, GL_FALSE, 5 * sizeof( float ), 0 );
GLint colAttrib = glGetAttribLocation( shaderProgram, "color" );
glEnableVertexAttribArray( colAttrib );
glVertexAttribPointer( colAttrib, 3, GL_FLOAT, GL_FALSE, 5 * sizeof( float ), (void*)( 2 * sizeof( float ) ) );
while ( glfwGetWindowParam(GLFW_OPENED) )
{
if ( glfwGetKey( GLFW_KEY_ESC ) == GLFW_PRESS )
break;
// Clear the screen to black
glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
glClear( GL_COLOR_BUFFER_BIT );
// Draw a rectangle from the 2 triangles using 6 indices
glDrawElements( GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0 );
// Swap buffers
glfwSwapBuffers();
}
glDeleteProgram( shaderProgram );
glDeleteShader( fragmentShader );
glDeleteShader( vertexShader );
glDeleteBuffers( 1, &ebo );
glDeleteBuffers( 1, &vbo );
glDeleteVertexArrays( 1, &vao );
}