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/*
* Test glRead/DrawPixels for GL_DEPTH_COMPONENT, with pixelzoom.
*
* Brian Paul
* 23 August 2003
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glew.h>
#include <GL/glut.h>
static GLint WinWidth = 500, WinHeight = 500;
static GLboolean Invert = GL_FALSE;
static void Display(void)
{
GLfloat depth[100 * 100];
GLfloat depth2[400 * 400];
GLfloat min, max;
int i;
glClearColor(0.5, 0.5, 0.5, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
/* draw a sphere */
glViewport(0, 0, 100, 100);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1, 1, -1, 1, -1, 0); /* clip away back half of sphere */
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glutSolidSphere(1.0, 20, 10);
/* read the depth image */
glReadPixels(0, 0, 100, 100, GL_DEPTH_COMPONENT, GL_FLOAT, depth);
min = max = depth[0];
for (i = 1; i < 100 * 100; i++) {
if (depth[i] < min)
min = depth[i];
if (depth[i] > max)
max = depth[i];
}
printf("Depth value range: [%f, %f]\n", min, max);
/* draw depth image with scaling (into z buffer) */
glPixelZoom(4.0, 4.0);
glColor4f(1, 0, 0, 0);
glWindowPos2i(100, 0);
if (Invert) {
glPixelTransferf(GL_DEPTH_SCALE, -1.0);
glPixelTransferf(GL_DEPTH_BIAS, 1.0);
}
glDrawPixels(100, 100, GL_DEPTH_COMPONENT, GL_FLOAT, depth);
if (Invert) {
glPixelTransferf(GL_DEPTH_SCALE, 1.0);
glPixelTransferf(GL_DEPTH_BIAS, 0.0);
}
glDisable(GL_DEPTH_TEST);
/* read back scaled depth image */
glReadPixels(100, 0, 400, 400, GL_DEPTH_COMPONENT, GL_FLOAT, depth2);
/* draw as luminance */
glPixelZoom(1.0, 1.0);
glDrawPixels(400, 400, GL_LUMINANCE, GL_FLOAT, depth2);
glutSwapBuffers();
}
static void Reshape(int width, int height)
{
WinWidth = width;
WinHeight = height;
glViewport(0, 0, width, height);
}
static void Key(unsigned char key, int x, int y)
{
(void) x;
(void) y;
switch (key) {
case 'i':
Invert = !Invert;
break;
case 27:
exit(0);
break;
}
glutPostRedisplay();
}
static void Init(void)
{
const GLfloat blue[4] = {.1, .1, 1.0, 1.0};
const GLfloat gray[4] = {0.2, 0.2, 0.2, 1.0};
const GLfloat white[4] = {1.0, 1.0, 1.0, 1.0};
const GLfloat pos[4] = {0, 0, 10, 0};
printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, blue);
glLightfv(GL_LIGHT0, GL_AMBIENT, gray);
glLightfv(GL_LIGHT0, GL_DIFFUSE, white);
glLightfv(GL_LIGHT0, GL_POSITION, pos);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
}
int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowPosition(0, 0);
glutInitWindowSize(WinWidth, WinHeight);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
glutCreateWindow(argv[0]);
glewInit();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Display);
Init();
glutMainLoop();
return 0;
}
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