initial check-in

progs/demos/occlude.c

@@ -0,0 +1,226 @@
+/*
+ * GL_HP_occlustion_test demo
+ *
+ * Brian Paul
+ * 31 March 2000
+ *
+ * Copyright (C) 2000  Brian Paul   All Rights Reserved.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <GL/glut.h>
+#include <GL/glext.h>
+
+
+static GLfloat Xpos = 0;
+
+
+static void
+PrintString(const char *s)
+{
+   while (*s) {
+      glutBitmapCharacter(GLUT_BITMAP_8_BY_13, (int) *s);
+      s++;
+   }
+}
+
+
+
+static void Idle(void)
+{
+   static int lastTime = 0;
+   static int sign = +1;
+   int time = glutGet(GLUT_ELAPSED_TIME);
+   float step;
+
+   if (lastTime == 0)
+      lastTime = time;
+   else if (time - lastTime < 20)  /* 50Hz update */
+      return;
+
+   step = (time - lastTime) / 1000.0 * sign;
+   lastTime = time;
+
+   Xpos += step;
+
+   if (Xpos > 2.5) {
+      Xpos = 2.5;
+      sign = -1;
+   }
+   else if (Xpos < -2.5) {
+      Xpos = -2.5;
+      sign = +1;
+   }
+   glutPostRedisplay();
+}
+
+
+static void Display( void )
+{
+   GLboolean result;
+
+   glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
+
+   glMatrixMode( GL_PROJECTION );
+   glLoadIdentity();
+   glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 25.0 );
+   glMatrixMode( GL_MODELVIEW );
+   glLoadIdentity();
+   glTranslatef( 0.0, 0.0, -15.0 );
+
+   /* draw the occluding polygons */
+   glColor3f(0, 0.6, 0.8);
+   glBegin(GL_QUADS);
+   glVertex2f(-1.6, -1.5);
+   glVertex2f(-0.4, -1.5);
+   glVertex2f(-0.4,  1.5);
+   glVertex2f(-1.6,  1.5);
+
+   glVertex2f( 0.4, -1.5);
+   glVertex2f( 1.6, -1.5);
+   glVertex2f( 1.6,  1.5);
+   glVertex2f( 0.4,  1.5);
+   glEnd();
+
+   /* draw the test polygon with occlusion testing */
+   glPushMatrix();
+   glTranslatef(Xpos, 0, -0.5);
+   glScalef(0.3, 0.3, 1.0);
+   glRotatef(-90.0 * Xpos, 0, 0, 1);
+
+   glEnable(GL_OCCLUSION_TEST_HP);  /* NOTE: enabling the occlusion test */
+                                    /* doesn't clear the result flag! */
+   glColorMask(0, 0, 0, 0);
+   glDepthMask(GL_FALSE);
+   /* this call clear's the result flag */
+   glGetBooleanv(GL_OCCLUSION_TEST_RESULT_HP, &result);
+
+   glBegin(GL_POLYGON);
+   glVertex3f(-1, -1, 0);
+   glVertex3f( 1, -1, 0);
+   glVertex3f( 1,  1, 0);
+   glVertex3f(-1,  1, 0);
+   glEnd();
+
+   glGetBooleanv(GL_OCCLUSION_TEST_RESULT_HP, &result);
+   /* turn off occlusion testing */
+   glDisable(GL_OCCLUSION_TEST_HP);
+   glColorMask(1, 1, 1, 1);
+   glDepthMask(GL_TRUE);
+
+   /* draw the green rect, so we can see what's going on */
+   glColor3f(0.8, 0.5, 0);
+   glBegin(GL_POLYGON);
+   glVertex3f(-1, -1, 0);
+   glVertex3f( 1, -1, 0);
+   glVertex3f( 1,  1, 0);
+   glVertex3f(-1,  1, 0);
+   glEnd();
+
+   glPopMatrix();
+
+
+   /* Print result message */
+   glMatrixMode( GL_PROJECTION );
+   glLoadIdentity();
+   glOrtho( -1.0, 1.0, -1.0, 1.0, -1.0, 1.0 );
+   glMatrixMode( GL_MODELVIEW );
+   glLoadIdentity();
+
+   glColor3f(1, 1, 1);
+   glRasterPos3f(-0.25, -0.7, 0);
+
+   if (result)
+      PrintString("   Visible");
+   else
+      PrintString("Fully Occluded");
+
+   glutSwapBuffers();
+}
+
+
+static void Reshape( int width, int height )
+{
+   glViewport( 0, 0, width, height );
+}
+
+
+static void Key( unsigned char key, int x, int y )
+{
+   (void) x;
+   (void) y;
+   switch (key) {
+      case 27:
+         exit(0);
+         break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void SpecialKey( int key, int x, int y )
+{
+   const GLfloat step = 0.1;
+   (void) x;
+   (void) y;
+   switch (key) {
+      case GLUT_KEY_LEFT:
+         Xpos -= step;
+         break;
+      case GLUT_KEY_RIGHT:
+         Xpos += step;
+         break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void Init( void )
+{
+   const char *ext = (const char *) glGetString(GL_EXTENSIONS);
+   if (!strstr(ext, "GL_HP_occlusion_test")) {
+      printf("Sorry, this demo requires the GL_HP_occlusion_test extension\n");
+      exit(-1);
+   }
+
+   glEnable(GL_DEPTH_TEST);
+}
+
+
+int main( int argc, char *argv[] )
+{
+   glutInit( &argc, argv );
+   glutInitWindowPosition( 0, 0 );
+   glutInitWindowSize( 400, 400 );
+   glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
+   glutCreateWindow(argv[0]);
+   glutReshapeFunc( Reshape );
+   glutKeyboardFunc( Key );
+   glutSpecialFunc( SpecialKey );
+   glutIdleFunc( Idle );
+   glutDisplayFunc( Display );
+   Init();
+   glutMainLoop();
+   return 0;
+}