quad-offset-units.c revision 32001f49 
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 "glut_wrap.h"
29
30GLenum doubleBuffer;
31
32static 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   fflush(stderr);
38
39    glClearColor(1.0, 1.0, 1.0, 0.0);
40}
41
42static void Reshape(int width, int height)
43{
44    glViewport(0, 0, (GLint)width, (GLint)height);
45
46    glMatrixMode(GL_PROJECTION);
47    glLoadIdentity();
48    glOrtho(-1.2, 1.2, -1.2, 1.2, -0.5, 1000.0);
49    glMatrixMode(GL_MODELVIEW);
50}
51
52static void Key(unsigned char key, int x, int y)
53{
54    switch (key) {
55      case 27:
56	exit(1);
57      default:
58	break;
59    }
60
61    glutPostRedisplay();
62}
63
64static void quad( float half )
65{
66   glBegin(GL_QUADS);
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   glVertex3f(-half/9.0, -half/9.0, -25.0 - half);
71   glEnd();
72}
73
74static void Draw(void)
75{
76   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
77   glEnable(GL_DEPTH_TEST);
78
79   /* red: offset back */
80   glEnable(GL_POLYGON_OFFSET_FILL);
81   glPolygonOffset(0, 4);
82   glColor3f(1,0,0);
83   quad(9);
84
85   /* black: no offset */
86   glDisable(GL_POLYGON_OFFSET_FILL);
87   glColor3f(0,0,0);
88   quad(6);
89
90   /* green: offset 0 (this should obscure the black quad) */
91   glEnable(GL_POLYGON_OFFSET_FILL);
92   glPolygonOffset(0, 0);
93   glDepthFunc( GL_EQUAL );
94   glColor3f(0,1,0);
95   quad(6);
96
97   /* blue: offset forward */
98   glDepthFunc( GL_LESS );
99   glPolygonOffset(0, -4);
100   glColor3f(0,0,1);
101   quad(3);
102
103   glDisable(GL_POLYGON_OFFSET_FILL);
104
105   glFlush();
106
107   if (doubleBuffer) {
108      glutSwapBuffers();
109   }
110}
111
112static GLenum Args(int argc, char **argv)
113{
114    GLint i;
115
116    doubleBuffer = GL_FALSE;
117
118    for (i = 1; i < argc; i++) {
119        if (strcmp(argv[i], "-sb") == 0) {
120	    doubleBuffer = GL_FALSE;
121	} else if (strcmp(argv[i], "-db") == 0) {
122	    doubleBuffer = GL_TRUE;
123	} else {
124	    fprintf(stderr, "%s (Bad option).\n", argv[i]);
125	    return GL_FALSE;
126	}
127    }
128    return GL_TRUE;
129}
130
131int main(int argc, char **argv)
132{
133    GLenum type;
134
135    glutInit(&argc, argv);
136
137    if (Args(argc, argv) == GL_FALSE) {
138	exit(1);
139    }
140
141    glutInitWindowPosition(0, 0); glutInitWindowSize( 250, 250);
142
143    type = GLUT_RGB | GLUT_ALPHA | GLUT_DEPTH;
144    type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
145    glutInitDisplayMode(type);
146
147    if (glutCreateWindow(*argv) == GL_FALSE) {
148	exit(1);
149    }
150
151    Init();
152
153    glutReshapeFunc(Reshape);
154    glutKeyboardFunc(Key);
155    glutDisplayFunc(Draw);
156    glutMainLoop();
157    return 0;
158}
159