progs/trivial/tri-z-eq.c

   1 /*
   2  * Copyright (c) 1991, 1992, 1993 Silicon Graphics, Inc.
   3  *
   4  * Permission to use, copy, modify, distribute, and sell this software and
   5  * its documentation for any purpose is hereby granted without fee, provided
   6  * that (i) the above copyright notices and this permission notice appear in
   7  * all copies of the software and related documentation, and (ii) the name of
   8  * Silicon Graphics may not be used in any advertising or
   9  * publicity relating to the software without the specific, prior written
  10  * permission of Silicon Graphics.
  11  *
  12  * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF
  13  * ANY KIND,
  14  * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
  15  * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
  16  *
  17  * IN NO EVENT SHALL SILICON GRAPHICS BE LIABLE FOR
  18  * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
  19  * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
  20  * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
  21  * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
  22  * OF THIS SOFTWARE.
  23  */
  24
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <stdlib.h>
  28 #include <GL/glut.h>
  29
  30
  31 #define CI_OFFSET_1 16
  32 #define CI_OFFSET_2 32
  33
  34
  35 GLenum doubleBuffer;
  36
  37 static void Init(void)
  38 {
  39    fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
  40    fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
  41    fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
  42    fflush(stderr);
  43
  44 }
  45
  46 static void Reshape(int width, int height)
  47 {
  48
  49     glViewport(0, 0, (GLint)width, (GLint)height);
  50
  51     glMatrixMode(GL_PROJECTION);
  52     glLoadIdentity();
  53     glOrtho(-1.0, 1.0, -1.0, 1.0, 1, -1);
  54     glMatrixMode(GL_MODELVIEW);
  55 }
  56
  57 static void Key(unsigned char key, int x, int y)
  58 {
  59
  60     switch (key) {
  61       case 27:
  62         exit(1);
  63       default:
  64         break;
  65     }
  66
  67     glutPostRedisplay();
  68 }
  69
  70 static void Draw(void)
  71 {
  72    float z = 1.0;
  73
  74    glClearColor(0.0, 0.0, 1.0, 0.0);
  75    glClearDepth(1.0);
  76    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  77    glDepthFunc(GL_EQUAL);
  78    glEnable(GL_DEPTH_TEST);
  79
  80    glBegin(GL_TRIANGLES);
  81    glColor3f(0,0,.7);
  82    glVertex3f( 0.9, -0.9, z);
  83    glColor3f(.8,0,0);
  84    glVertex3f( 0.9,  0.9, z);
  85    glColor3f(0,.9,0);
  86    glVertex3f(-0.9,  0.0, z);
  87    glEnd();
  88
  89    glFlush();
  90
  91    {
  92       GLfloat z;
  93       glReadPixels(125, 125, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &z);
  94       printf("Z at (125, 125) = %f\n", z);
  95    }
  96
  97    if (doubleBuffer) {
  98       glutSwapBuffers();
  99    }
 100 }
 101
 102 static GLenum Args(int argc, char **argv)
 103 {
 104     GLint i;
 105
 106     doubleBuffer = GL_FALSE;
 107
 108     for (i = 1; i < argc; i++) {
 109         if (strcmp(argv[i], "-sb") == 0) {
 110             doubleBuffer = GL_FALSE;
 111         } else if (strcmp(argv[i], "-db") == 0) {
 112             doubleBuffer = GL_TRUE;
 113         } else {
 114             fprintf(stderr, "%s (Bad option).\n", argv[i]);
 115             return GL_FALSE;
 116         }
 117     }
 118     return GL_TRUE;
 119 }
 120
 121 int main(int argc, char **argv)
 122 {
 123     GLenum type;
 124
 125     glutInit(&argc, argv);
 126
 127     if (Args(argc, argv) == GL_FALSE) {
 128         exit(1);
 129     }
 130
 131     glutInitWindowPosition(100, 0); glutInitWindowSize( 250, 250);
 132
 133     type = GLUT_RGB | GLUT_DEPTH;
 134     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 135     glutInitDisplayMode(type);
 136
 137     if (glutCreateWindow(*argv) == GL_FALSE) {
 138         exit(1);
 139     }
 140
 141     Init();
 142
 143     glutReshapeFunc(Reshape);
 144     glutKeyboardFunc(Key);
 145     glutDisplayFunc(Draw);
 146     glutMainLoop();
 147         return 0;
 148 }