--- /dev/null
+/*
+ * GL_ARB_occlustion_query demo
+ *
+ * Brian Paul
+ * 12 June 2003
+ *
+ * Copyright (C) 2003 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 <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#define GL_GLEXT_PROTOTYPES
+#include <GL/glut.h>
+
+
+static GLfloat Xpos = 0;
+static GLuint OccQuery;
+
+
+
+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 )
+{
+ GLuint passed;
+ GLint ready;
+ char s[100];
+
+ 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);
+
+ glBeginQueryARB(GL_SAMPLES_PASSED_ARB, OccQuery);
+
+ glColorMask(0, 0, 0, 0);
+ glDepthMask(GL_FALSE);
+
+ glBegin(GL_POLYGON);
+ glVertex3f(-1, -1, 0);
+ glVertex3f( 1, -1, 0);
+ glVertex3f( 1, 1, 0);
+ glVertex3f(-1, 1, 0);
+ glEnd();
+
+ glEndQueryARB(GL_SAMPLES_PASSED_ARB);
+
+ do {
+ /* do useful work here, if any */
+ glGetQueryObjectivARB(OccQuery, GL_QUERY_RESULT_AVAILABLE_ARB, &ready);
+ } while (!ready);
+ glGetQueryObjectuivARB(OccQuery, GL_QUERY_RESULT_ARB, &passed);
+
+ /* turn off occlusion testing */
+ glColorMask(1, 1, 1, 1);
+ glDepthMask(GL_TRUE);
+
+ /* draw the orange 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);
+ sprintf(s, " %4d Fragments Visible", passed);
+ glRasterPos3f(-0.50, -0.7, 0);
+ PrintString(s);
+ if (!passed) {
+ glRasterPos3f(-0.25, -0.8, 0);
+ 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);
+ GLint bits;
+
+ if (!strstr(ext, "GL_ARB_occlusion_query")) {
+ printf("Sorry, this demo requires the GL_ARB_occlusion_query extension\n");
+ exit(-1);
+ }
+
+ glGetQueryivARB(GL_SAMPLES_PASSED_ARB, GL_QUERY_COUNTER_BITS_ARB, &bits);
+ if (!bits) {
+ printf("Hmmm, GL_QUERY_COUNTER_BITS_ARB is zero!\n");
+ exit(-1);
+ }
+
+ glGenQueriesARB(1, &OccQuery);
+ assert( glIsQueryARB(OccQuery) );
+
+ 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;
+}
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