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