[source=cpp]
//
// This code was created by Jeff Molofee '99 (ported to Linux/GLUT by Richard Campbell '99)
//
// If you've found this code useful, please let me know.
//
// Visit me at www.demonews.com/hosted/nehe 
// (email Richard Campbell at ulmont@bellsouth.net)
//
#include <GL/glut.h>    // Header File For The GLUT Library 
#include <GL/gl.h> // Header File For The OpenGL32 Library
#include <GL/glu.h> // Header File For The GLu32 Library
#include <unistd.h>     // Header File For sleeping.

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

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

/* rotation angle for the triangle. */
float rtri = 0.0f;

/* rotation angle for the quadrilateral. */
float rquad = 0.0f;
float pos=0; // Triangle position
/* A general OpenGL initialization function.  Sets all of the initial parameters. */
void InitGL(int Width, int Height)         // We call this right after our OpenGL window is created.
{
  glClearColor(1.0f, 0.0f, 0.0f, 0.0f);  // This Will Clear The Background Color To Black
  glClearDepth(1.0);    // Enables Clearing Of The Depth Buffer
  glDepthFunc(GL_LESS);    // The Type Of Depth Test To Do
  glEnable(GL_DEPTH_TEST);   // Enables Depth Testing
  glShadeModel(GL_SMOOTH);   // Enables Smooth Color Shading

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();    // Reset The Projection Matrix

  gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f); // Calculate The Aspect Ratio Of The Window

  glMatrixMode(GL_MODELVIEW);
}

/* The function called when our window is resized (which shouldn't happen, 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 Depth Buffer
  glLoadIdentity();    // Reset The View

  glTranslatef(-1.5f + pos,0.0f,-6.0f);  // Move Left 1.5 Units And Into The Screen 6.0
 
  glRotatef(rtri,0.0f,1.0f,0.0f);  // Rotate The Triangle On The Y axis 
  // draw a triangle (in smooth coloring 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 done with the polygon (smooth color interpolation)

  glLoadIdentity();    // make sure we're no longer rotated.
  glTranslatef(1.5f,0.0f,-6.0f);  // Move Right 3 Units, and back into the screen 6.0
 
  glRotatef(rquad,1.0f,0.0f,0.0f);  // Rotate The Quad On The X axis 
  // draw a square (quadrilateral)
  glColor3f(0.5f,0.5f,1.0f);   // set color to a blue shade.
  glBegin(GL_QUADS);    // start drawing a polygon (4 sided)
  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

  rtri+=1.0f;     // Increase The Rotation Variable For The Triangle
  rquad-=1.0f;     // Decrease The Rotation Variable For The Quad 

  // swap the buffers to display, since double buffering is used.
  glutSwapBuffers();
  
}
void idle()
{
 
 DrawGLScene();
}
/* The function called whenever a key is pressed. */
void keyPressed(unsigned char key, int x, int y) 
{
    /* sleep to avoid thrashing this procedure */
    //usleep(10);

    /* If escape is pressed, kill everything. */
 //pos = (GLfloat)x/(GLfloat)y;
 if (key == '3')
 {
  pos += 0.1;
 }
 if(key == '2')
  pos -= 0.1;
    if (key == ESCAPE) 
    { 
 /* shut down our window */
 glutDestroyWindow(window); 
 
 /* exit the program...normal termination. */
 exit(0);                   
    }
}

int main(int argc, char **argv) 
{  
  /* Initialize GLUT state - glut will take any command line arguments that pertain to it or 
     X Windows - look at its documentation at http://reality.sgi.com/mjk/spec3/spec3.html */