progs/tests/zreaddraw.c

   1 /*
   2  * Test glRead/DrawPixels for GL_DEPTH_COMPONENT, with pixelzoom.
   3  *
   4  * Brian Paul
   5  * 23 August 2003
   6  */
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <math.h>
  11 #include <GL/glew.h>
  12 #include <GL/glut.h>
  13
  14 static GLint WinWidth = 500, WinHeight = 500;
  15
  16
  17 static void Display(void)
  18 {
  19    GLfloat depth[100 * 100];
  20    GLfloat depth2[400 * 400];
  21    GLfloat min, max;
  22    int i;
  23
  24    glClearColor(0.5, 0.5, 0.5, 1.0);
  25    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  26
  27    glEnable(GL_DEPTH_TEST);
  28
  29    /* draw a sphere */
  30    glViewport(0, 0, 100, 100);
  31    glMatrixMode(GL_PROJECTION);
  32    glLoadIdentity();
  33    glOrtho(-1, 1, -1, 1, -1, 0);  /* clip away back half of sphere */
  34    glMatrixMode(GL_MODELVIEW);
  35    glLoadIdentity();
  36    glutSolidSphere(1.0, 20, 10);
  37
  38    /* read the depth image */
  39    glReadPixels(0, 0, 100, 100, GL_DEPTH_COMPONENT, GL_FLOAT, depth);
  40    min = max = depth[0];
  41    for (i = 1; i < 100 * 100; i++) {
  42       if (depth[i] < min)
  43          min = depth[i];
  44       if (depth[i] > max)
  45          max = depth[i];
  46    }
  47    printf("Depth value range: [%f, %f]\n", min, max);
  48
  49    /* draw depth image with scaling (into z buffer) */
  50    glPixelZoom(4.0, 4.0);
  51    glColor4f(1, 0, 0, 0);
  52    glWindowPos2i(100, 0);
  53    glDrawPixels(100, 100, GL_DEPTH_COMPONENT, GL_FLOAT, depth);
  54
  55    glDisable(GL_DEPTH_TEST);
  56
  57    /* read back scaled depth image */
  58    glReadPixels(100, 0, 400, 400, GL_DEPTH_COMPONENT, GL_FLOAT, depth2);
  59    /* draw as luminance */
  60    glPixelZoom(1.0, 1.0);
  61    glDrawPixels(400, 400, GL_LUMINANCE, GL_FLOAT, depth2);
  62
  63    glutSwapBuffers();
  64 }
  65
  66
  67 static void Reshape(int width, int height)
  68 {
  69    WinWidth = width;
  70    WinHeight = height;
  71    glViewport(0, 0, width, height);
  72 }
  73
  74
  75 static void Key(unsigned char key, int x, int y)
  76 {
  77    (void) x;
  78    (void) y;
  79    switch (key) {
  80       case 27:
  81          exit(0);
  82          break;
  83    }
  84    glutPostRedisplay();
  85 }
  86
  87
  88 static void Init(void)
  89 {
  90    const GLfloat blue[4] = {.1, .1, 1.0, 1.0};
  91    const GLfloat gray[4] = {0.2, 0.2, 0.2, 1.0};
  92    const GLfloat white[4] = {1.0, 1.0, 1.0, 1.0};
  93    const GLfloat pos[4] = {0, 0, 10, 0};
  94
  95    printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
  96    printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
  97
  98    glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, blue);
  99    glLightfv(GL_LIGHT0, GL_AMBIENT, gray);
 100    glLightfv(GL_LIGHT0, GL_DIFFUSE, white);
 101    glLightfv(GL_LIGHT0, GL_POSITION, pos);
 102    glEnable(GL_LIGHTING);
 103    glEnable(GL_LIGHT0);
 104 }
 105
 106
 107 int main(int argc, char *argv[])
 108 {
 109    glutInit(&argc, argv);
 110    glutInitWindowPosition(0, 0);
 111    glutInitWindowSize(WinWidth, WinHeight);
 112    glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
 113    glutCreateWindow(argv[0]);
 114    glewInit();
 115    glutReshapeFunc(Reshape);
 116    glutKeyboardFunc(Key);
 117    glutDisplayFunc(Display);
 118    Init();
 119    glutMainLoop();
 120    return 0;
 121 }