hi guys, i have made a sample shading program for running a simple OpenGL2.0 proram in windows.
Hope this will be helpful for beginners in OpenGL.
/* Using the standard output for fprintf */
#include <stdio.h>
#include <stdlib.h>
/* Use glew.h instead of gl.h to get all the GL prototypes declared */
#include <GL/glew.h>
#include <GL/GL.h>
/* Using the GLUT library for the base windowing setup */
#include <GL/glut.h>
#pragma comment(lib, "glew32.lib")
GLuint program;
GLint positionHandle;
GLint colorHandle;
GLfloat triangle_vertices[] = {
0.0f, 0.8f,
-0.8f, -0.8f,
0.8f, -0.8f
};
const char *fs_source =
"#version 120
"
"uniform vec3 uColor;"
"void main(void) { "
" gl_FragColor = vec4(uColor, 1.0);"
"}";
const char *vs_source =
#ifdef GL_ES_VERSION_2_0
"#version 100
" // OpenGL ES 2.0
#else
"#version 120
" // OpenGL 2.1
#endif
"attribute vec2 aPosition; "
"void main(void) { "
" gl_Position = vec4(aPosition, 0.0, 1.0); "
"}";
int showError(const char*, const char*);
//Returns 1 when all is ok, 0 with a displayed error
int init_resources(void)
{
GLint compile_ok = GL_FALSE;
GLint link_ok = GL_FALSE;
GLuint vertexHandle = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexHandle, 1, &vs_source, NULL);
glCompileShader(vertexHandle);
glGetShaderiv(vertexHandle, GL_COMPILE_STATUS, &compile_ok);
if (0 == compile_ok)
{
fprintf(stderr, "Error in vertex shader
");
return 0;
}
GLuint fragHandle = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragHandle, 1, &fs_source, NULL);
glCompileShader(fragHandle);
glGetShaderiv(fragHandle, GL_COMPILE_STATUS, &compile_ok);
if (!compile_ok) {
fprintf(stderr, "Error in fragment shader
");
return 0;
}
program = glCreateProgram();
glAttachShader(program, vertexHandle);
glAttachShader(program, fragHandle);
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &link_ok);
if (!link_ok) {
fprintf(stderr, "glLinkProgram:");
return 0;
}
const char* aPosition = "aPosition";
const char* uColor = "uColor";
positionHandle = glGetAttribLocation(program, aPosition);
colorHandle = glGetUniformLocation(program, uColor);
showError(aPosition, uColor);
return 1;
}
int showError(const char* aPosition, const char* uColor)
{
if (positionHandle == -1) {
fprintf(stderr, "Could not bind attribute %s
", aPosition);
return 0;
}
if (colorHandle == -1) {
fprintf(stderr, "Could not show color %s
", uColor);
return 0;
}
}
void onDisplay()
{
/* Clear the background as white */
glClearColor(1.0, 1.0, 1.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(program);
glUniform3f(colorHandle, 1.0f, 0.0f, 0.0f);
glEnableVertexAttribArray(positionHandle);
glVertexAttribPointer(positionHandle, 2, GL_FLOAT,GL_FALSE, 0, triangle_vertices);
/* Push each element in buffer_vertices to the vertex shader */
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(positionHandle);
/* Display the result */
glutSwapBuffers();
}
void free_resources()
{
glDeleteProgram(program);
}
int main(int argc, char* argv[])
{
/* Glut-related initialising functions */
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGBA|GLUT_DOUBLE|GLUT_DEPTH);
glutInitWindowSize(640, 480);
glutCreateWindow("My First Triangle");
/* Extension wrangler initialising */
GLenum glew_status = glewInit();
if (glew_status != GLEW_OK)
{
fprintf(stderr, "Error: %s
", glewGetErrorString(glew_status));
return EXIT_FAILURE;
}
/* When all init functions run without errors,
the program can initialise the resources */
if (1 == init_resources())
{
/* We can display it if everything goes OK */
glutDisplayFunc(onDisplay);
glutMainLoop();
}
/* If the program exits in the usual way,
free resources and exit with a success */
free_resources();
return EXIT_SUCCESS;
}
Do ask any question what so ever is bothering you going through this code.