progs/trivial/tri-stencil.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 <stdlib.h>
  27 #include <string.h>
  28 #include <math.h>
  29 #include <GL/glut.h>
  30
  31
  32 static void Init(void)
  33 {
  34 }
  35
  36 static void Reshape(int width, int height)
  37 {
  38
  39     glViewport(0, 0, (GLint)width, (GLint)height);
  40
  41     glMatrixMode(GL_PROJECTION);
  42     glLoadIdentity();
  43     glOrtho(-5.0, 5.0, -5.0, 5.0, -5.0, 5.0);
  44     glMatrixMode(GL_MODELVIEW);
  45 }
  46
  47 static void Key(unsigned char key, int x, int y)
  48 {
  49
  50     switch (key) {
  51       case 27:
  52         printf("Exiting...\n");
  53         exit(1);
  54       case 'r':
  55         printf("Redisplaying...\n");
  56         glutPostRedisplay();
  57         break;
  58       default:
  59         printf("No such key '%c'...\n", key);
  60         break;
  61     }
  62 }
  63
  64 static void Draw(void)
  65 {
  66    glShadeModel(GL_FLAT);
  67
  68    {
  69       glClearColor(0.0, 0.0, 0.0, 0.0);
  70       glClearStencil(0);
  71       glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);
  72    }
  73
  74
  75    glStencilMask(1);
  76    glEnable(GL_STENCIL_TEST);
  77    glStencilFunc(GL_ALWAYS, 1, 1);
  78    glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
  79
  80    /* red triangle (setting stencil to 1) */
  81    glColor3ub(200, 0, 0);
  82    glBegin(GL_POLYGON);
  83    glVertex3i(-4, -4, 0);
  84    glVertex3i( 4, -4, 0);
  85    glVertex3i( 0,  4, 0);
  86    glEnd();
  87
  88 #if 1
  89    glStencilFunc(GL_EQUAL, 1, 1);
  90    glStencilOp(GL_INCR, GL_KEEP, GL_DECR);
  91
  92    /* green quad (if over red, decr stencil to 0, else incr to 1) */
  93    glColor3ub(0, 200, 0);
  94    glBegin(GL_POLYGON);
  95    glVertex3i(3, 3, 0);
  96    glVertex3i(-3, 3, 0);
  97    glVertex3i(-3, -3, 0);
  98    glVertex3i(3, -3, 0);
  99    glEnd();
 100 #endif
 101
 102 #if 1
 103    glStencilFunc(GL_EQUAL, 1, 1);
 104    glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
 105
 106    /* blue quad (where stencil == 1) */
 107    glColor3ub(0, 0, 200);
 108    glBegin(GL_POLYGON);
 109    glVertex3f(2.5, 2.5, 0);
 110    glVertex3f(-2.5, 2.5, 0);
 111    glVertex3f(-2.5, -2.5, 0);
 112    glVertex3f(2.5, -2.5, 0);
 113    glEnd();
 114 #endif
 115
 116    glFlush();
 117 }
 118
 119 static GLenum Args(int argc, char **argv)
 120 {
 121     GLint i;
 122
 123
 124     for (i = 1; i < argc; i++) {
 125         if (strcmp(argv[i], "-dr") == 0) {
 126         } else {
 127             printf("%s (Bad option).\n", argv[i]);
 128             return GL_FALSE;
 129         }
 130     }
 131     return GL_TRUE;
 132 }
 133
 134 int main(int argc, char **argv)
 135 {
 136     GLenum type;
 137
 138     glutInit(&argc, argv);
 139
 140     if (Args(argc, argv) == GL_FALSE) {
 141         exit(1);
 142     }
 143
 144     glutInitWindowPosition(0, 0);
 145     glutInitWindowSize( 300, 300);
 146
 147     type = GLUT_RGB | GLUT_SINGLE | GLUT_DEPTH | GLUT_STENCIL;
 148     glutInitDisplayMode(type);
 149
 150     if (glutCreateWindow(*argv) == GL_FALSE) {
 151         exit(1);
 152     }
 153
 154     Init();
 155
 156     glutReshapeFunc(Reshape);
 157     glutKeyboardFunc(Key);
 158     glutDisplayFunc(Draw);
 159     glutMainLoop();
 160         return 0;
 161 }