progs/demos/occlude.c

   1 /*
   2  * GL_HP_occlustion_test demo
   3  *
   4  * Brian Paul
   5  * 31 March 2000
   6  *
   7  * Copyright (C) 2000  Brian Paul   All Rights Reserved.
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a
  10  * copy of this software and associated documentation files (the "Software"),
  11  * to deal in the Software without restriction, including without limitation
  12  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  13  * and/or sell copies of the Software, and to permit persons to whom the
  14  * Software is furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included
  17  * in all copies or substantial portions of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  20  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  22  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  23  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  24  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  */
  26
  27
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include <math.h>
  32 #include <GL/glut.h>
  33 #include <GL/glext.h>
  34
  35
  36 static GLfloat Xpos = 0;
  37
  38
  39 static void
  40 PrintString(const char *s)
  41 {
  42    while (*s) {
  43       glutBitmapCharacter(GLUT_BITMAP_8_BY_13, (int) *s);
  44       s++;
  45    }
  46 }
  47
  48
  49
  50 static void Idle(void)
  51 {
  52    static int lastTime = 0;
  53    static int sign = +1;
  54    int time = glutGet(GLUT_ELAPSED_TIME);
  55    float step;
  56
  57    if (lastTime == 0)
  58       lastTime = time;
  59    else if (time - lastTime < 20)  /* 50Hz update */
  60       return;
  61
  62    step = (time - lastTime) / 1000.0 * sign;
  63    lastTime = time;
  64
  65    Xpos += step;
  66
  67    if (Xpos > 2.5) {
  68       Xpos = 2.5;
  69       sign = -1;
  70    }
  71    else if (Xpos < -2.5) {
  72       Xpos = -2.5;
  73       sign = +1;
  74    }
  75    glutPostRedisplay();
  76 }
  77
  78
  79 static void Display( void )
  80 {
  81    GLboolean result;
  82
  83    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
  84
  85    glMatrixMode( GL_PROJECTION );
  86    glLoadIdentity();
  87    glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 25.0 );
  88    glMatrixMode( GL_MODELVIEW );
  89    glLoadIdentity();
  90    glTranslatef( 0.0, 0.0, -15.0 );
  91
  92    /* draw the occluding polygons */
  93    glColor3f(0, 0.6, 0.8);
  94    glBegin(GL_QUADS);
  95    glVertex2f(-1.6, -1.5);
  96    glVertex2f(-0.4, -1.5);
  97    glVertex2f(-0.4,  1.5);
  98    glVertex2f(-1.6,  1.5);
  99
 100    glVertex2f( 0.4, -1.5);
 101    glVertex2f( 1.6, -1.5);
 102    glVertex2f( 1.6,  1.5);
 103    glVertex2f( 0.4,  1.5);
 104    glEnd();
 105
 106    /* draw the test polygon with occlusion testing */
 107    glPushMatrix();
 108    glTranslatef(Xpos, 0, -0.5);
 109    glScalef(0.3, 0.3, 1.0);
 110    glRotatef(-90.0 * Xpos, 0, 0, 1);
 111
 112    glEnable(GL_OCCLUSION_TEST_HP);  /* NOTE: enabling the occlusion test */
 113                                     /* doesn't clear the result flag! */
 114    glColorMask(0, 0, 0, 0);
 115    glDepthMask(GL_FALSE);
 116    /* this call clear's the result flag.  Not really needed for this demo. */
 117    glGetBooleanv(GL_OCCLUSION_TEST_RESULT_HP, &result);
 118
 119    glBegin(GL_POLYGON);
 120    glVertex3f(-1, -1, 0);
 121    glVertex3f( 1, -1, 0);
 122    glVertex3f( 1,  1, 0);
 123    glVertex3f(-1,  1, 0);
 124    glEnd();
 125
 126    glGetBooleanv(GL_OCCLUSION_TEST_RESULT_HP, &result);
 127    /* turn off occlusion testing */
 128    glDisable(GL_OCCLUSION_TEST_HP);
 129    glColorMask(1, 1, 1, 1);
 130    glDepthMask(GL_TRUE);
 131
 132    /* draw the green rect, so we can see what's going on */
 133    glColor3f(0.8, 0.5, 0);
 134    glBegin(GL_POLYGON);
 135    glVertex3f(-1, -1, 0);
 136    glVertex3f( 1, -1, 0);
 137    glVertex3f( 1,  1, 0);
 138    glVertex3f(-1,  1, 0);
 139    glEnd();
 140
 141    glPopMatrix();
 142
 143
 144    /* Print result message */
 145    glMatrixMode( GL_PROJECTION );
 146    glLoadIdentity();
 147    glOrtho( -1.0, 1.0, -1.0, 1.0, -1.0, 1.0 );
 148    glMatrixMode( GL_MODELVIEW );
 149    glLoadIdentity();
 150
 151    glColor3f(1, 1, 1);
 152    glRasterPos3f(-0.25, -0.7, 0);
 153
 154    if (result)
 155       PrintString("   Visible");
 156    else
 157       PrintString("Fully Occluded");
 158
 159    glutSwapBuffers();
 160 }
 161
 162
 163 static void Reshape( int width, int height )
 164 {
 165    glViewport( 0, 0, width, height );
 166 }
 167
 168
 169 static void Key( unsigned char key, int x, int y )
 170 {
 171    (void) x;
 172    (void) y;
 173    switch (key) {
 174       case 27:
 175          exit(0);
 176          break;
 177    }
 178    glutPostRedisplay();
 179 }
 180
 181
 182 static void SpecialKey( int key, int x, int y )
 183 {
 184    const GLfloat step = 0.1;
 185    (void) x;
 186    (void) y;
 187    switch (key) {
 188       case GLUT_KEY_LEFT:
 189          Xpos -= step;
 190          break;
 191       case GLUT_KEY_RIGHT:
 192          Xpos += step;
 193          break;
 194    }
 195    glutPostRedisplay();
 196 }
 197
 198
 199 static void Init( void )
 200 {
 201    const char *ext = (const char *) glGetString(GL_EXTENSIONS);
 202    if (!strstr(ext, "GL_HP_occlusion_test")) {
 203       printf("Sorry, this demo requires the GL_HP_occlusion_test extension\n");
 204       exit(-1);
 205    }
 206
 207    glEnable(GL_DEPTH_TEST);
 208 }
 209
 210
 211 int main( int argc, char *argv[] )
 212 {
 213    glutInit( &argc, argv );
 214    glutInitWindowPosition( 0, 0 );
 215    glutInitWindowSize( 400, 400 );
 216    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
 217    glutCreateWindow(argv[0]);
 218    glutReshapeFunc( Reshape );
 219    glutKeyboardFunc( Key );
 220    glutSpecialFunc( SpecialKey );
 221    glutIdleFunc( Idle );
 222    glutDisplayFunc( Display );
 223    Init();
 224    glutMainLoop();
 225    return 0;
 226 }