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/**
* Test glDrawPixels(GL_DEPTH_COMPONENT)
*
* We load a window-sized buffer of Z values so that Z=1 at the top and
* Z=0 at the bottom (and interpolate between).
* We draw that image into the Z buffer, then draw an ordinary cube.
* The bottom part of the cube should be "clipped" where the cube fails
* the Z test.
*
* Press 'd' to view the Z buffer as a grayscale image.
*/
#define GL_GLEXT_PROTOTYPES
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
#include "../util/showbuffer.c"
static int Win;
static GLfloat Xrot = 50, Yrot = 40, Zpos = 6;
static GLboolean Anim = GL_FALSE;
static int Width = 200, Height = 200;
static GLfloat *z;
static GLboolean showZ = 0;
static void
Idle(void)
{
Xrot += 3.0;
Yrot += 4.0;
glutPostRedisplay();
}
static void
Draw(void)
{
glClearColor(0, 0, 0.5, 0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
#if 1
glColor3f(1, 0, 0);
glWindowPos2i(0,0);
glColorMask(0,0,0,0);
glDrawPixels(Width, Height, GL_DEPTH_COMPONENT, GL_FLOAT, z);
#elif 0
glPushMatrix();
glTranslatef(-0.75, 0, Zpos);
glutSolidSphere(1.0, 20, 10);
glPopMatrix();
#endif
glColorMask(1,1,1,1);
/* draw cube */
glPushMatrix();
glTranslatef(0, 0, Zpos);
glRotatef(Xrot, 1, 0, 0);
glRotatef(Yrot, 0, 1, 0);
glutSolidCube(2.0);
glPopMatrix();
#if 0
/* drawpixels after cube */
glColor3f(1, 0, 0);
glWindowPos2i(0,0);
//glColorMask(0,0,0,0);
glDrawPixels(Width, Height, GL_DEPTH_COMPONENT, GL_FLOAT, z);
#endif
if (showZ) {
ShowDepthBuffer(Width, Height, 0.0, 1.0);
}
glutSwapBuffers();
}
static void
Reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 30.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, -15.0);
Width = width;
Height = height;
z = (float *) malloc(width * height * 4);
{
int i, j, k = 0;
for (i = 0; i < height; i++) {
float zval = (float) i / (height - 1);
for (j = 0; j < width; j++) {
z[k++] = zval;
}
}
}
}
static void
Key(unsigned char key, int x, int y)
{
const GLfloat step = 1.0;
(void) x;
(void) y;
switch (key) {
case 'a':
Anim = !Anim;
if (Anim)
glutIdleFunc(Idle);
else
glutIdleFunc(NULL);
break;
case 'd':
showZ = !showZ;
break;
case 'z':
Zpos -= step;
break;
case 'Z':
Zpos += step;
break;
case 27:
glutDestroyWindow(Win);
exit(0);
break;
}
glutPostRedisplay();
}
static void
SpecialKey(int key, int x, int y)
{
const GLfloat step = 3.0;
(void) x;
(void) y;
switch (key) {
case GLUT_KEY_UP:
Xrot -= step;
break;
case GLUT_KEY_DOWN:
Xrot += step;
break;
case GLUT_KEY_LEFT:
Yrot -= step;
break;
case GLUT_KEY_RIGHT:
Yrot += step;
break;
}
glutPostRedisplay();
}
static void
Init(void)
{
/* setup lighting, etc */
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
}
int
main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowPosition(0, 0);
glutInitWindowSize(400, 400);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
Win = glutCreateWindow(argv[0]);
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutSpecialFunc(SpecialKey);
glutDisplayFunc(Draw);
if (Anim)
glutIdleFunc(Idle);
Init();
glutMainLoop();
return 0;
}
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