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 static GLboolean Invert = GL_FALSE;
  16
  17
  18 static void Display(void)
  19 {
  20    GLfloat depth[100 * 100];
  21    GLfloat depth2[400 * 400];
  22    GLfloat min, max;
  23    int i;
  24
  25    glClearColor(0.5, 0.5, 0.5, 1.0);
  26    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  27
  28    glEnable(GL_DEPTH_TEST);
  29
  30    /* draw a sphere */
  31    glViewport(0, 0, 100, 100);
  32    glMatrixMode(GL_PROJECTION);
  33    glLoadIdentity();
  34    glOrtho(-1, 1, -1, 1, -1, 0);  /* clip away back half of sphere */
  35    glMatrixMode(GL_MODELVIEW);
  36    glLoadIdentity();
  37    glutSolidSphere(1.0, 20, 10);
  38
  39    /* read the depth image */
  40    glReadPixels(0, 0, 100, 100, GL_DEPTH_COMPONENT, GL_FLOAT, depth);
  41    min = max = depth[0];
  42    for (i = 1; i < 100 * 100; i++) {
  43       if (depth[i] < min)
  44          min = depth[i];
  45       if (depth[i] > max)
  46          max = depth[i];
  47    }
  48    printf("Depth value range: [%f, %f]\n", min, max);
  49
  50    /* draw depth image with scaling (into z buffer) */
  51    glPixelZoom(4.0, 4.0);
  52    glColor4f(1, 0, 0, 0);
  53    glWindowPos2i(100, 0);
  54    if (Invert) {
  55       glPixelTransferf(GL_DEPTH_SCALE, -1.0);
  56       glPixelTransferf(GL_DEPTH_BIAS, 1.0);
  57    }
  58    glDrawPixels(100, 100, GL_DEPTH_COMPONENT, GL_FLOAT, depth);
  59    if (Invert) {
  60       glPixelTransferf(GL_DEPTH_SCALE, 1.0);
  61       glPixelTransferf(GL_DEPTH_BIAS, 0.0);
  62    }
  63
  64    glDisable(GL_DEPTH_TEST);
  65
  66    /* read back scaled depth image */
  67    glReadPixels(100, 0, 400, 400, GL_DEPTH_COMPONENT, GL_FLOAT, depth2);
  68    /* draw as luminance */
  69    glPixelZoom(1.0, 1.0);
  70    glDrawPixels(400, 400, GL_LUMINANCE, GL_FLOAT, depth2);
  71
  72    glutSwapBuffers();
  73 }
  74
  75
  76 static void Reshape(int width, int height)
  77 {
  78    WinWidth = width;
  79    WinHeight = height;
  80    glViewport(0, 0, width, height);
  81 }
  82
  83
  84 static void Key(unsigned char key, int x, int y)
  85 {
  86    (void) x;
  87    (void) y;
  88    switch (key) {
  89       case 'i':
  90          Invert = !Invert;
  91          break;
  92       case 27:
  93          exit(0);
  94          break;
  95    }
  96    glutPostRedisplay();
  97 }
  98
  99
 100 static void Init(void)
 101 {
 102    const GLfloat blue[4] = {.1, .1, 1.0, 1.0};
 103    const GLfloat gray[4] = {0.2, 0.2, 0.2, 1.0};
 104    const GLfloat white[4] = {1.0, 1.0, 1.0, 1.0};
 105    const GLfloat pos[4] = {0, 0, 10, 0};
 106
 107    printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
 108    printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
 109
 110    glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, blue);
 111    glLightfv(GL_LIGHT0, GL_AMBIENT, gray);
 112    glLightfv(GL_LIGHT0, GL_DIFFUSE, white);
 113    glLightfv(GL_LIGHT0, GL_POSITION, pos);
 114    glEnable(GL_LIGHTING);
 115    glEnable(GL_LIGHT0);
 116 }
 117
 118
 119 int main(int argc, char *argv[])
 120 {
 121    glutInit(&argc, argv);
 122    glutInitWindowPosition(0, 0);
 123    glutInitWindowSize(WinWidth, WinHeight);
 124    glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
 125    glutCreateWindow(argv[0]);
 126    glewInit();
 127    glutReshapeFunc(Reshape);
 128    glutKeyboardFunc(Key);
 129    glutDisplayFunc(Display);
 130    Init();
 131    glutMainLoop();
 132    return 0;
 133 }