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/*
* Exercise GL_EXT_fog_coord
*/
#define GL_GLEXT_PROTOTYPES
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
static int Width = 600;
static int Height = 200;
static GLfloat Near = 5.0, Far = 25.0;
static void Display( void )
{
GLfloat t;
glClearColor(0.2, 0.2, 0.8, 0);
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
for (t = 0.0; t <= 1.0; t += 0.25) {
GLfloat f = Near + t * (Far - Near);
printf("glFogCoord(%4.1f)\n", f);
glFogCoordfEXT(f);
glPushMatrix();
glTranslatef(t * 10.0 - 5.0, 0, 0);
glBegin(GL_POLYGON);
glVertex2f(-1, -1);
glVertex2f( 1, -1);
glVertex2f( 1, 1);
glVertex2f(-1, 1);
glEnd();
glPopMatrix();
}
glutSwapBuffers();
}
static void Reshape( int width, int height )
{
GLfloat ar = (float) width / (float) height;
Width = width;
Height = height;
glViewport( 0, 0, width, height );
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glFrustum( -ar, ar, -1.0, 1.0, Near, Far );
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glTranslatef( 0.0, 0.0, -15.0 );
}
static void Key( unsigned char key, int x, int y )
{
(void) x;
(void) y;
switch (key) {
case 27:
exit(0);
break;
}
glutPostRedisplay();
}
static void Init( void )
{
printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
/* setup lighting, etc */
if (!glutExtensionSupported("GL_EXT_fog_coord")) {
printf("Sorry, this program requires GL_EXT_fog_coord\n");
exit(1);
}
glFogi(GL_FOG_COORDINATE_SOURCE_EXT, GL_FOG_COORDINATE_EXT);
glFogi(GL_FOG_MODE, GL_LINEAR);
glFogf(GL_FOG_START, Near);
glFogf(GL_FOG_END, Far);
glEnable(GL_FOG);
printf("Squares should be colored from white -> gray -> black.\n");
}
int main( int argc, char *argv[] )
{
glutInit( &argc, argv );
glutInitWindowPosition( 0, 0 );
glutInitWindowSize( Width, Height );
glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
glutCreateWindow(argv[0]);
glutReshapeFunc( Reshape );
glutKeyboardFunc( Key );
glutDisplayFunc( Display );
Init();
glutMainLoop();
return 0;
}
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