progs/tests/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 static GLboolean Anim = GL_TRUE;
  38
  39
  40 static void
  41 PrintString(const char *s)
  42 {
  43    while (*s) {
  44       glutBitmapCharacter(GLUT_BITMAP_8_BY_13, (int) *s);
  45       s++;
  46    }
  47 }
  48
  49
  50
  51 static void Idle(void)
  52 {
  53    static int lastTime = 0;
  54    static int sign = +1;
  55    int time = glutGet(GLUT_ELAPSED_TIME);
  56    float step;
  57
  58    if (lastTime == 0)
  59       lastTime = time;
  60    else if (time - lastTime < 20)  /* 50Hz update */
  61       return;
  62
  63    step = (time - lastTime) / 1000.0 * sign;
  64    lastTime = time;
  65
  66    Xpos += step;
  67
  68    if (Xpos > 2.5) {
  69       Xpos = 2.5;
  70       sign = -1;
  71    }
  72    else if (Xpos < -2.5) {
  73       Xpos = -2.5;
  74       sign = +1;
  75    }
  76    glutPostRedisplay();
  77 }
  78
  79
  80 static void Display( void )
  81 {
  82    GLboolean result;
  83
  84    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
  85
  86    glMatrixMode( GL_PROJECTION );
  87    glLoadIdentity();
  88    glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 25.0 );
  89    glMatrixMode( GL_MODELVIEW );
  90    glLoadIdentity();
  91    glTranslatef( 0.0, 0.0, -15.0 );
  92
  93    /* draw the occluding polygons */
  94    glColor3f(0, 0.6, 0.8);
  95    glBegin(GL_QUADS);
  96    glVertex2f(-1.6, -1.5);
  97    glVertex2f(-0.4, -1.5);
  98    glVertex2f(-0.4,  1.5);
  99    glVertex2f(-1.6,  1.5);
 100
 101    glVertex2f( 0.4, -1.5);
 102    glVertex2f( 1.6, -1.5);
 103    glVertex2f( 1.6,  1.5);
 104    glVertex2f( 0.4,  1.5);
 105    glEnd();
 106
 107    /* draw the test polygon with occlusion testing */
 108    glPushMatrix();
 109    glTranslatef(Xpos, 0, -0.5);
 110    glScalef(0.3, 0.3, 1.0);
 111    glRotatef(-90.0 * Xpos, 0, 0, 1);
 112
 113    glEnable(GL_OCCLUSION_TEST_HP);  /* NOTE: enabling the occlusion test */
 114                                     /* doesn't clear the result flag! */
 115    glColorMask(0, 0, 0, 0);
 116    glDepthMask(GL_FALSE);
 117    /* this call clear's the result flag.  Not really needed for this demo. */
 118    glGetBooleanv(GL_OCCLUSION_TEST_RESULT_HP, &result);
 119
 120    glBegin(GL_POLYGON);
 121    glVertex3f(-1, -1, 0);
 122    glVertex3f( 1, -1, 0);
 123    glVertex3f( 1,  1, 0);
 124    glVertex3f(-1,  1, 0);
 125    glEnd();
 126
 127    glGetBooleanv(GL_OCCLUSION_TEST_RESULT_HP, &result);
 128    /* turn off occlusion testing */
 129    glDisable(GL_OCCLUSION_TEST_HP);
 130    glColorMask(1, 1, 1, 1);
 131    glDepthMask(GL_TRUE);
 132
 133    /* draw the green rect, so we can see what's going on */
 134    glColor3f(0.8, 0.5, 0);
 135    glBegin(GL_POLYGON);
 136    glVertex3f(-1, -1, 0);
 137    glVertex3f( 1, -1, 0);
 138    glVertex3f( 1,  1, 0);
 139    glVertex3f(-1,  1, 0);
 140    glEnd();
 141
 142    glPopMatrix();
 143
 144
 145    /* Print result message */
 146    glMatrixMode( GL_PROJECTION );
 147    glLoadIdentity();
 148    glOrtho( -1.0, 1.0, -1.0, 1.0, -1.0, 1.0 );
 149    glMatrixMode( GL_MODELVIEW );
 150    glLoadIdentity();
 151
 152    glColor3f(1, 1, 1);
 153    glRasterPos3f(-0.25, -0.7, 0);
 154
 155    if (result)
 156       PrintString("   Visible");
 157    else
 158       PrintString("Fully Occluded");
 159
 160    glutSwapBuffers();
 161 }
 162
 163
 164 static void Reshape( int width, int height )
 165 {
 166    glViewport( 0, 0, width, height );
 167 }
 168
 169
 170 static void Key( unsigned char key, int x, int y )
 171 {
 172    (void) x;
 173    (void) y;
 174    switch (key) {
 175       case 'a':
 176          Anim = !Anim;
 177          if (Anim)
 178             glutIdleFunc( Idle );
 179          else
 180             glutIdleFunc( NULL );
 181          break;
 182       case 27:
 183          exit(0);
 184          break;
 185    }
 186    glutPostRedisplay();
 187 }
 188
 189
 190 static void SpecialKey( int key, int x, int y )
 191 {
 192    const GLfloat step = 0.1;
 193    (void) x;
 194    (void) y;
 195    switch (key) {
 196       case GLUT_KEY_LEFT:
 197          Xpos -= step;
 198          break;
 199       case GLUT_KEY_RIGHT:
 200          Xpos += step;
 201          break;
 202    }
 203    glutPostRedisplay();
 204 }
 205
 206
 207 static void Init( void )
 208 {
 209    const char *ext = (const char *) glGetString(GL_EXTENSIONS);
 210    if (!strstr(ext, "GL_HP_occlusion_test")) {
 211       printf("Sorry, this demo requires the GL_HP_occlusion_test extension\n");
 212       exit(-1);
 213    }
 214
 215    glEnable(GL_DEPTH_TEST);
 216 }
 217
 218
 219 int main( int argc, char *argv[] )
 220 {
 221    glutInit( &argc, argv );
 222    glutInitWindowPosition( 0, 0 );
 223    glutInitWindowSize( 400, 400 );
 224    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
 225    glutCreateWindow(argv[0]);
 226    glutReshapeFunc( Reshape );
 227    glutKeyboardFunc( Key );
 228    glutSpecialFunc( SpecialKey );
 229    glutIdleFunc( Idle );
 230    glutDisplayFunc( Display );
 231    Init();
 232    glutMainLoop();
 233    return 0;
 234 }