progs/tests/fogcoord.c

   1 /*
   2  * Exercise GL_EXT_fog_coord
   3  */
   4
   5
   6 #define GL_GLEXT_PROTOTYPES
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <math.h>
  10 #include <GL/glut.h>
  11
  12 static int Width = 600;
  13 static int Height = 200;
  14 static GLfloat Near = 5.0, Far = 25.0;
  15
  16
  17 static void Display( void )
  18 {
  19    GLfloat t;
  20
  21    glClearColor(0.2, 0.2, 0.8, 0);
  22    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
  23
  24    for (t = 0.0; t <= 1.0; t += 0.25) {
  25       GLfloat f = -(Near + t * (Far - Near));
  26       glFogCoordfEXT(f);
  27
  28       glPushMatrix();
  29          glTranslatef(t * 10.0 - 5.0, 0, 0);
  30          glBegin(GL_POLYGON);
  31          glVertex2f(-1, -1);
  32          glVertex2f( 1, -1);
  33          glVertex2f( 1,  1);
  34          glVertex2f(-1,  1);
  35          glEnd();
  36       glPopMatrix();
  37    }
  38    glutSwapBuffers();
  39 }
  40
  41
  42 static void Reshape( int width, int height )
  43 {
  44    GLfloat ar = (float) width / (float) height;
  45    Width = width;
  46    Height = height;
  47    glViewport( 0, 0, width, height );
  48    glMatrixMode( GL_PROJECTION );
  49    glLoadIdentity();
  50    glFrustum( -ar, ar, -1.0, 1.0, Near, Far );
  51    glMatrixMode( GL_MODELVIEW );
  52    glLoadIdentity();
  53    glTranslatef( 0.0, 0.0, -15.0 );
  54 }
  55
  56
  57 static void Key( unsigned char key, int x, int y )
  58 {
  59    (void) x;
  60    (void) y;
  61    switch (key) {
  62       case 27:
  63          exit(0);
  64          break;
  65    }
  66    glutPostRedisplay();
  67 }
  68
  69
  70 static void Init( void )
  71 {
  72    /* setup lighting, etc */
  73    if (!glutExtensionSupported("GL_EXT_fog_coord")) {
  74       printf("Sorry, this program requires GL_EXT_fog_coord\n");
  75       exit(1);
  76    }
  77    glFogi(GL_FOG_COORDINATE_SOURCE_EXT, GL_FOG_COORDINATE_EXT);
  78    glFogi(GL_FOG_MODE, GL_LINEAR);
  79    glFogf(GL_FOG_START, Near);
  80    glFogf(GL_FOG_END, Far);
  81    glEnable(GL_FOG);
  82    printf("Squares should be colored from white -> gray -> black.\n");
  83 }
  84
  85
  86 int main( int argc, char *argv[] )
  87 {
  88    glutInit( &argc, argv );
  89    glutInitWindowPosition( 0, 0 );
  90    glutInitWindowSize( Width, Height );
  91    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
  92    glutCreateWindow(argv[0]);
  93    glutReshapeFunc( Reshape );
  94    glutKeyboardFunc( Key );
  95    glutDisplayFunc( Display );
  96    Init();
  97    glutMainLoop();
  98    return 0;
  99 }