progs/trivial/quad-offset-units.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 GLenum doubleBuffer;
  31
  32 static void Init(void)
  33 {
  34    fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
  35    fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
  36    fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
  37
  38     glClearColor(1.0, 1.0, 1.0, 0.0);
  39 }
  40
  41 static void Reshape(int width, int height)
  42 {
  43     glViewport(0, 0, (GLint)width, (GLint)height);
  44
  45     glMatrixMode(GL_PROJECTION);
  46     glLoadIdentity();
  47     glOrtho(-1.2, 1.2, -1.2, 1.2, -0.5, 1000.0);
  48     glMatrixMode(GL_MODELVIEW);
  49 }
  50
  51 static void Key(unsigned char key, int x, int y)
  52 {
  53     switch (key) {
  54       case 27:
  55         exit(1);
  56       default:
  57         return;
  58     }
  59
  60     glutPostRedisplay();
  61 }
  62
  63 static void quad( float half )
  64 {
  65    glBegin(GL_QUADS);
  66    glVertex3f( half/9.0, -half/9.0, -25.0 + half);
  67    glVertex3f( half/9.0,  half/9.0, -25.0 + half);
  68    glVertex3f(-half/9.0,  half/9.0, -25.0 - half);
  69    glVertex3f(-half/9.0, -half/9.0, -25.0 - half);
  70    glEnd();
  71 }
  72
  73 static void Draw(void)
  74 {
  75    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  76    glEnable(GL_DEPTH_TEST);
  77
  78    /* red: offset back */
  79    glEnable(GL_POLYGON_OFFSET_FILL);
  80    glPolygonOffset(0, 4);
  81    glColor3f(1,0,0);
  82    quad(9);
  83
  84    /* black: no offset */
  85    glDisable(GL_POLYGON_OFFSET_FILL);
  86    glColor3f(0,0,0);
  87    quad(6);
  88
  89    /* green: offset 0 (this should obscure the black quad) */
  90    glEnable(GL_POLYGON_OFFSET_FILL);
  91    glPolygonOffset(0, 0);
  92    glDepthFunc( GL_EQUAL );
  93    glColor3f(0,1,0);
  94    quad(6);
  95
  96    /* blue: offset forward */
  97    glDepthFunc( GL_LESS );
  98    glPolygonOffset(0, -4);
  99    glColor3f(0,0,1);
 100    quad(3);
 101
 102    glDisable(GL_POLYGON_OFFSET_FILL);
 103
 104    glFlush();
 105
 106    if (doubleBuffer) {
 107       glutSwapBuffers();
 108    }
 109 }
 110
 111 static GLenum Args(int argc, char **argv)
 112 {
 113     GLint i;
 114
 115     doubleBuffer = GL_FALSE;
 116
 117     for (i = 1; i < argc; i++) {
 118         if (strcmp(argv[i], "-sb") == 0) {
 119             doubleBuffer = GL_FALSE;
 120         } else if (strcmp(argv[i], "-db") == 0) {
 121             doubleBuffer = GL_TRUE;
 122         } else {
 123             fprintf(stderr, "%s (Bad option).\n", argv[i]);
 124             return GL_FALSE;
 125         }
 126     }
 127     return GL_TRUE;
 128 }
 129
 130 int main(int argc, char **argv)
 131 {
 132     GLenum type;
 133
 134     glutInit(&argc, argv);
 135
 136     if (Args(argc, argv) == GL_FALSE) {
 137         exit(1);
 138     }
 139
 140     glutInitWindowPosition(0, 0); glutInitWindowSize( 250, 250);
 141
 142     type = GLUT_RGB | GLUT_ALPHA | GLUT_DEPTH;
 143     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 144     glutInitDisplayMode(type);
 145
 146     if (glutCreateWindow(*argv) == GL_FALSE) {
 147         exit(1);
 148     }
 149
 150     Init();
 151
 152     glutReshapeFunc(Reshape);
 153     glutKeyboardFunc(Key);
 154     glutDisplayFunc(Draw);
 155     glutMainLoop();
 156     return 0;
 157 }