#include <GLUT/GLUT.h>
#include <OpenGL/OpenGL.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

/* ASCII code for the escape key. */
#define ESCAPE  27

/* The number of our GLUT window */
int window;

/* A general OpenGL initializtion function. Sets all of teh initial parameters. */
/* We call this right after our OpenGL window is created. */
void initGL(int width, int height) {
	glClearColor(0.0f, 0.0f, 0.0f, 0.0f); // this will Clear the background color 
										  // to black
	glClearDepth(1.0);		// Enables Clearting Of the depth buffer
	glDepthFunc(GL_LESS); 		// The type of depth test to do
	glEnable(GL_DEPTH_TEST); 		// Enable Depth Testing.
	glShadeModel(GL_SMOOTH); 		// Enable smooth color shading

	glMatrixMode(GL_PROJECTION); 	
	glLoadIdentity(); 				// Reset the projection matrix

	// @see: http://hi.baidu.com/korndorben/item/76c5020453f18212cc34ea90
	gluPerspective(45.0f, (GLfloat)width / (GLfloat)height, 0.1f, 100.0f); // Calcuate the aspect ratio of teh window

	glMatrixMode(GL_MODELVIEW);
}

/* The function called when our window is resized 
   (which shouldn't happend, because we're fullscreen) */
void resizeGLScene(int width, int height) {
	if (height == 0) // Prevent a divide by zero if the window is too small
		height = 1;

	glViewport(0, 0, width, height); // Reset the current Viewport and perspective 
									 // transformation
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	gluPerspective(45.0f, (GLfloat)width / (GLfloat)height, 0.1f, 100.0f);
	glMatrixMode(GL_MODELVIEW);
}

/* The main drawing function */
void drawGLScene() {
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear the screen and
														// the dpeth buffer
	glLoadIdentity(); 	// Reset the view

	glTranslatef(-1.5f, 0.0f, -6.0f); 	// Move Left 1.5 units And into the screen 6.0

	// draw a triangle (in smooth colring mode)
	glBegin(GL_POLYGON); // start drawing a polygon
		glColor3f(1.0f, 0.0f, 0.0f);	// set the color to red
		glVertex3f(0.0f, 1.0f, 0.0f);   // top

		glColor3f(0.0f, 1.0f, 0.0f); 	// Set the Color to green.
		glVertex3f(1.0f, -1.0f, 0.0f); 	// bottom right

		glColor3f(0.0f, 0.0f, 1.0f); 	// set the color to blue.
		glVertex3f(-1.0f, -1.0f, 0.0f); // bottom left
	glEnd();		// We're down with the polygon (smooth color interpolation);

	glTranslatef(3.0f, 0.0f, 0.0f);

	// draw a square (quadrilateral)
	glColor3f(0.5f, 0.5f, 1.0f); // set color to a blue shade.
	glBegin(GL_QUADS);
		glVertex3f(-1.0f, 1.0f, 0.0f);		// Top left
		glVertex3f( 1.0f, 1.0f, 0.0f);		// top right
		glVertex3f( 1.0f, -1.0f, 0.0f);		// bottom right
		glVertex3f(-1.0f, -1.0f, 0.0f); 	// bottom left
	glEnd();					// Done with the polygon

	// we need ot swap the buffer to display our drawing.
	glutSwapBuffers();
}

/* The function called whenever a key is pressed. */
void keyPressed(unsigned char key, int x, int y) {
	usleep(100); // sleep to avoid thrashing this procedure */

	/* If escape is pressd, kill everything. */
	if (key == ESCAPE) {
		/* shut down our window. */
		glutDestroyWindow(window);

		/* exit the program...normal termination. */
		exit(0);
	}
}

int main(int argc, char **argv) {
	glutInit(&argc, argv);

	/* Select type of Display mode:
		Double buffer
		RGBA color
		Alpha components supported
		Depth buffer */
	glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH);

	/* GET A 640 X 360 window */
	glutInitWindowSize(640, 480);

	/* the window starts at the upper left corner of the screen. */
	glutInitWindowPosition(0, 0);

	/* Open a window */
	window = glutCreateWindow("Jeff Molofee's GL Code Tutorial ... NeHe 'oo");

	/* Register the function to do all our OpenGL drawing. */
	glutDisplayFunc(&drawGLScene);

	/* Go fullscree. Tis is as soon as possible. */
	//glutFullScreen();

	/* Even if there are no events, redraw our gl scene. */
	glutIdleFunc(&drawGLScene);

	/* Register the function called when our window is resized. */
	glutReshapeFunc(&resizeGLScene);

	/* Register the function called when the keyboard is pressed. */
	glutKeyboardFunc(&keyPressed);

	/* Initialize our window. */
	initGL(640, 480);

	/* Start event procesing engine */
	glutMainLoop();

	return 1;
}

Mac OS X 运行：

$: clang -o lession lession3.c -Wno-deprecated -framework OpenGL -framework GLUT

$: ./lession

结果：一个三角形。一个正方形。

neHe OpenGL lession 3