progs/tests/zdrawpix.c

   1 /**
   2  * Test glDrawPixels(GL_DEPTH_COMPONENT)
   3  *
   4  * We load a window-sized buffer of Z values so that Z=1 at the top and
   5  * Z=0 at the bottom (and interpolate between).
   6  * We draw that image into the Z buffer, then draw an ordinary cube.
   7  * The bottom part of the cube should be "clipped" where the cube fails
   8  * the Z test.
   9  *
  10  * Press 'd' to view the Z buffer as a grayscale image.
  11  */
  12
  13 #define GL_GLEXT_PROTOTYPES
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <math.h>
  17 #include <GL/glut.h>
  18 #include "../util/showbuffer.c"
  19
  20
  21 static int Win;
  22 static GLfloat Xrot = 50, Yrot = 40, Zpos = 6;
  23 static GLboolean Anim = GL_FALSE;
  24
  25 static int Width = 200, Height = 200;
  26 static GLfloat *z;
  27 static GLboolean showZ = 0;
  28
  29
  30 static void
  31 Idle(void)
  32 {
  33    Xrot += 3.0;
  34    Yrot += 4.0;
  35    glutPostRedisplay();
  36 }
  37
  38
  39 static void
  40 Draw(void)
  41 {
  42    glClearColor(0, 0, 0.5, 0);
  43    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  44
  45 #if 1
  46    glColor3f(1, 0, 0);
  47    glWindowPos2i(0,0);
  48    glColorMask(0,0,0,0);
  49    glDrawPixels(Width, Height, GL_DEPTH_COMPONENT, GL_FLOAT, z);
  50 #elif 0
  51    glPushMatrix();
  52    glTranslatef(-0.75, 0, Zpos);
  53    glutSolidSphere(1.0, 20, 10);
  54    glPopMatrix();
  55 #endif
  56    glColorMask(1,1,1,1);
  57
  58    /* draw cube */
  59    glPushMatrix();
  60    glTranslatef(0, 0, Zpos);
  61    glRotatef(Xrot, 1, 0, 0);
  62    glRotatef(Yrot, 0, 1, 0);
  63    glutSolidCube(2.0);
  64    glPopMatrix();
  65
  66 #if 0
  67    /* drawpixels after cube */
  68    glColor3f(1, 0, 0);
  69    glWindowPos2i(0,0);
  70    //glColorMask(0,0,0,0);
  71    glDrawPixels(Width, Height, GL_DEPTH_COMPONENT, GL_FLOAT, z);
  72 #endif
  73
  74    if (showZ) {
  75       ShowDepthBuffer(Width, Height, 0.0, 1.0);
  76    }
  77
  78    glutSwapBuffers();
  79 }
  80
  81
  82 static void
  83 Reshape(int width, int height)
  84 {
  85    glViewport(0, 0, width, height);
  86    glMatrixMode(GL_PROJECTION);
  87    glLoadIdentity();
  88    glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 30.0);
  89    glMatrixMode(GL_MODELVIEW);
  90    glLoadIdentity();
  91    glTranslatef(0.0, 0.0, -15.0);
  92
  93    Width = width;
  94    Height = height;
  95
  96    z = (float *) malloc(width * height * 4);
  97    {
  98       int i, j, k = 0;
  99       for (i = 0; i < height; i++) {
 100          float zval = (float) i / (height - 1);
 101          for (j = 0; j < width; j++) {
 102             z[k++] = zval;
 103          }
 104       }
 105    }
 106 }
 107
 108
 109 static void
 110 Key(unsigned char key, int x, int y)
 111 {
 112    const GLfloat step = 1.0;
 113    (void) x;
 114    (void) y;
 115    switch (key) {
 116       case 'a':
 117          Anim = !Anim;
 118          if (Anim)
 119             glutIdleFunc(Idle);
 120          else
 121             glutIdleFunc(NULL);
 122          break;
 123       case 'd':
 124          showZ = !showZ;
 125          break;
 126       case 'z':
 127          Zpos -= step;
 128          break;
 129       case 'Z':
 130          Zpos += step;
 131          break;
 132       case 27:
 133          glutDestroyWindow(Win);
 134          exit(0);
 135          break;
 136    }
 137    glutPostRedisplay();
 138 }
 139
 140
 141 static void
 142 SpecialKey(int key, int x, int y)
 143 {
 144    const GLfloat step = 3.0;
 145    (void) x;
 146    (void) y;
 147    switch (key) {
 148       case GLUT_KEY_UP:
 149          Xrot -= step;
 150          break;
 151       case GLUT_KEY_DOWN:
 152          Xrot += step;
 153          break;
 154       case GLUT_KEY_LEFT:
 155          Yrot -= step;
 156          break;
 157       case GLUT_KEY_RIGHT:
 158          Yrot += step;
 159          break;
 160    }
 161    glutPostRedisplay();
 162 }
 163
 164
 165 static void
 166 Init(void)
 167 {
 168    /* setup lighting, etc */
 169    glEnable(GL_DEPTH_TEST);
 170    glEnable(GL_LIGHTING);
 171    glEnable(GL_LIGHT0);
 172 }
 173
 174
 175 int
 176 main(int argc, char *argv[])
 177 {
 178    glutInit(&argc, argv);
 179    glutInitWindowPosition(0, 0);
 180    glutInitWindowSize(400, 400);
 181    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
 182    Win = glutCreateWindow(argv[0]);
 183    glutReshapeFunc(Reshape);
 184    glutKeyboardFunc(Key);
 185    glutSpecialFunc(SpecialKey);
 186    glutDisplayFunc(Draw);
 187    if (Anim)
 188       glutIdleFunc(Idle);
 189    Init();
 190    glutMainLoop();
 191    return 0;
 192 }