progs/trivial/tri-cull.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 static GLenum doubleBuffer;
  31 static GLint cullmode = 0;
  32 static GLenum front = GL_CCW; /* GL default */
  33
  34 static void cull(void)
  35 {
  36    cullmode = (cullmode + 1) % 4;
  37    if (cullmode == 0) {
  38       glCullFace(GL_FRONT);
  39       glEnable(GL_CULL_FACE);
  40       printf("cull GL_FRONT\n");
  41    }
  42    else if (cullmode == 1) {
  43       glCullFace(GL_BACK);
  44       glEnable(GL_CULL_FACE);
  45       printf("cull GL_BACK\n");
  46    }
  47    else if (cullmode == 2) {
  48       glCullFace(GL_FRONT_AND_BACK);
  49       glEnable(GL_CULL_FACE);
  50       printf("cull GL_FRONT_AND_BACK\n");
  51    }
  52    else {
  53       glDisable(GL_CULL_FACE);
  54       printf("cull none\n");
  55    }
  56 }
  57
  58 static void Init(void)
  59 {
  60    fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
  61    fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
  62    fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
  63    glClearColor(0.0, 0.0, 1.0, 0.0);
  64    cull();
  65 }
  66
  67 static void Reshape(int width, int height)
  68 {
  69     glViewport(0, 0, (GLint)width, (GLint)height);
  70
  71     glMatrixMode(GL_PROJECTION);
  72     glLoadIdentity();
  73     glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
  74     glMatrixMode(GL_MODELVIEW);
  75 }
  76
  77 static void Key(unsigned char key, int x, int y)
  78 {
  79    switch (key) {
  80    case 27:
  81       exit(1);
  82    case 'c':
  83       cull();
  84       break;
  85    case 'f':
  86       front = ((front == GL_CCW) ? GL_CW : GL_CCW);
  87       glFrontFace(front);
  88       printf("front face = %s\n", front == GL_CCW ? "GL_CCW" : "GL_CW");
  89       break;
  90    default:
  91       return;
  92    }
  93    glutPostRedisplay();
  94 }
  95
  96 static void Draw(void)
  97 {
  98    glClear(GL_COLOR_BUFFER_BIT);
  99
 100    glBegin(GL_TRIANGLES);
 101    /* CCW / front-facing */
 102    glColor3f(0,0,.7);
 103    glVertex3f(-0.1, -0.9, -30.0);
 104    glColor3f(.8,0,0);
 105    glVertex3f(-0.1,  0.9, -30.0);
 106    glColor3f(0,.9,0);
 107    glVertex3f(-0.9,  0.0, -30.0);
 108
 109    /* CW / back-facing */
 110    glColor3f(0,0,.7);
 111    glVertex3f( 0.1, -0.9, -30.0);
 112    glColor3f(.8,0,0);
 113    glVertex3f( 0.1,  0.9, -30.0);
 114    glColor3f(0,.9,0);
 115    glVertex3f( 0.9,  0.0, -30.0);
 116
 117    glEnd();
 118
 119    glFlush();
 120
 121    if (doubleBuffer) {
 122       glutSwapBuffers();
 123    }
 124 }
 125
 126 static GLenum Args(int argc, char **argv)
 127 {
 128     GLint i;
 129
 130     doubleBuffer = GL_FALSE;
 131
 132     for (i = 1; i < argc; i++) {
 133         if (strcmp(argv[i], "-sb") == 0) {
 134             doubleBuffer = GL_FALSE;
 135         } else if (strcmp(argv[i], "-db") == 0) {
 136             doubleBuffer = GL_TRUE;
 137         } else {
 138             fprintf(stderr, "%s (Bad option).\n", argv[i]);
 139             return GL_FALSE;
 140         }
 141     }
 142     return GL_TRUE;
 143 }
 144
 145 int main(int argc, char **argv)
 146 {
 147     GLenum type;
 148
 149     glutInit(&argc, argv);
 150
 151     if (Args(argc, argv) == GL_FALSE) {
 152         exit(1);
 153     }
 154
 155     glutInitWindowPosition(0, 0); glutInitWindowSize( 250, 250);
 156
 157     type = GLUT_RGB | GLUT_ALPHA;
 158     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 159     glutInitDisplayMode(type);
 160
 161     if (glutCreateWindow("First Tri") == GL_FALSE) {
 162         exit(1);
 163     }
 164
 165     Init();
 166
 167     glutReshapeFunc(Reshape);
 168     glutKeyboardFunc(Key);
 169     glutDisplayFunc(Draw);
 170     glutMainLoop();
 171     return 0;
 172 }