progs/redbook/stencil.c

   1
   2 /* Copyright (c) Mark J. Kilgard, 1994. */
   3
   4 /*
   5  * (c) Copyright 1993, Silicon Graphics, Inc.
   6  * ALL RIGHTS RESERVED
   7  * Permission to use, copy, modify, and distribute this software for
   8  * any purpose and without fee is hereby granted, provided that the above
   9  * copyright notice appear in all copies and that both the copyright notice
  10  * and this permission notice appear in supporting documentation, and that
  11  * the name of Silicon Graphics, Inc. not be used in advertising
  12  * or publicity pertaining to distribution of the software without specific,
  13  * written prior permission.
  14  *
  15  * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
  16  * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
  18  * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
  19  * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
  20  * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
  21  * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
  22  * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
  23  * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
  24  * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
  25  * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
  26  * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
  27  *
  28  * US Government Users Restricted Rights
  29  * Use, duplication, or disclosure by the Government is subject to
  30  * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
  31  * (c)(1)(ii) of the Rights in Technical Data and Computer Software
  32  * clause at DFARS 252.227-7013 and/or in similar or successor
  33  * clauses in the FAR or the DOD or NASA FAR Supplement.
  34  * Unpublished-- rights reserved under the copyright laws of the
  35  * United States.  Contractor/manufacturer is Silicon Graphics,
  36  * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
  37  *
  38  * OpenGL(TM) is a trademark of Silicon Graphics, Inc.
  39  */
  40 /*  stencil.c
  41  *  This program draws two rotated tori in a window.
  42  *  A diamond in the center of the window masks out part
  43  *  of the scene.  Within this mask, a different model
  44  *  (a sphere) is drawn in a different color.
  45  */
  46
  47 /*
  48  * !!! NOTE !!!
  49  *
  50  * This demo is poorly written.  The stencil buffer should be
  51  * redrawn in display(), not in the myReshape() function.
  52  * The reason is if the window gets "damaged" then the stencil buffer
  53  * contents will be in an undefined state (myReshape is not called when
  54  * a window is damaged and needs to be redrawn).  If the stencil buffer
  55  * contents are undefined, the results of display() are unpredictable.
  56  *
  57  * -Brian
  58  */
  59
  60
  61 #include <stdlib.h>
  62 #include <GL/glut.h>
  63
  64 #define YELLOWMAT   1
  65 #define BLUEMAT 2
  66
  67 static void myinit (void)
  68 {
  69     GLfloat yellow_diffuse[] = { 0.7, 0.7, 0.0, 1.0 };
  70     GLfloat yellow_specular[] = { 1.0, 1.0, 1.0, 1.0 };
  71
  72     GLfloat blue_diffuse[] = { 0.1, 0.1, 0.7, 1.0 };
  73     GLfloat blue_specular[] = { 0.1, 1.0, 1.0, 1.0 };
  74
  75     GLfloat position_one[] = { 1.0, 1.0, 1.0, 0.0 };
  76
  77     glNewList(YELLOWMAT, GL_COMPILE);
  78     glMaterialfv(GL_FRONT, GL_DIFFUSE, yellow_diffuse);
  79     glMaterialfv(GL_FRONT, GL_SPECULAR, yellow_specular);
  80     glMaterialf(GL_FRONT, GL_SHININESS, 64.0);
  81     glEndList();
  82
  83     glNewList(BLUEMAT, GL_COMPILE);
  84     glMaterialfv(GL_FRONT, GL_DIFFUSE, blue_diffuse);
  85     glMaterialfv(GL_FRONT, GL_SPECULAR, blue_specular);
  86     glMaterialf(GL_FRONT, GL_SHININESS, 45.0);
  87     glEndList();
  88
  89     glLightfv(GL_LIGHT0, GL_POSITION, position_one);
  90
  91     glEnable(GL_LIGHT0);
  92     glEnable(GL_LIGHTING);
  93     glDepthFunc(GL_LESS);
  94     glEnable(GL_DEPTH_TEST);
  95
  96     glClearStencil(0x0);
  97     glEnable(GL_STENCIL_TEST);
  98
  99 }
 100
 101 /*  Draw a sphere in a diamond-shaped section in the
 102  *  middle of a window with 2 tori.
 103  */
 104 static void display(void)
 105 {
 106     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 107
 108     glStencilOp (GL_KEEP, GL_KEEP, GL_KEEP);
 109
 110 /* draw blue sphere where the stencil is 1 */
 111     glStencilFunc (GL_EQUAL, 0x1, 0x1);
 112     glCallList (BLUEMAT);
 113     glutSolidSphere (0.5, 15, 15);
 114
 115 /* draw the tori where the stencil is not 1 */
 116     glStencilFunc (GL_NOTEQUAL, 0x1, 0x1);
 117     glPushMatrix();
 118         glRotatef (45.0, 0.0, 0.0, 1.0);
 119         glRotatef (45.0, 0.0, 1.0, 0.0);
 120         glCallList (YELLOWMAT);
 121         glutSolidTorus (0.275, 0.85, 15, 15);
 122         glPushMatrix();
 123             glRotatef (90.0, 1.0, 0.0, 0.0);
 124             glutSolidTorus (0.275, 0.85, 15, 15);
 125         glPopMatrix();
 126     glPopMatrix();
 127
 128     glFlush();
 129     glutSwapBuffers();
 130 }
 131
 132 /*  Whenever the window is reshaped, redefine the
 133  *  coordinate system and redraw the stencil area.
 134  */
 135 static void myReshape(int w, int h)
 136 {
 137     glViewport(0, 0, w, h);
 138
 139     glClear(GL_STENCIL_BUFFER_BIT);
 140 /* create a diamond shaped stencil area */
 141     glMatrixMode(GL_PROJECTION);
 142     glLoadIdentity();
 143     glOrtho(-3.0, 3.0, -3.0, 3.0, -1.0, 1.0);
 144     glMatrixMode(GL_MODELVIEW);
 145     glLoadIdentity();
 146
 147     glStencilFunc (GL_ALWAYS, 0x1, 0x1);
 148     glStencilOp (GL_REPLACE, GL_REPLACE, GL_REPLACE);
 149     glBegin(GL_QUADS);
 150         glVertex3f (-1.0, 0.0, 0.0);
 151         glVertex3f (0.0, 1.0, 0.0);
 152         glVertex3f (1.0, 0.0, 0.0);
 153         glVertex3f (0.0, -1.0, 0.0);
 154     glEnd();
 155
 156     glMatrixMode(GL_PROJECTION);
 157     glLoadIdentity();
 158     gluPerspective(45.0, (GLfloat) w/(GLfloat) h, 3.0, 7.0);
 159     glMatrixMode(GL_MODELVIEW);
 160     glLoadIdentity();
 161     glTranslatef(0.0, 0.0, -5.0);
 162 }
 163
 164 static void
 165 key(unsigned char k, int x, int y)
 166 {
 167   switch (k) {
 168   case 27:  /* Escape */
 169     exit(0);
 170     break;
 171   default:
 172     return;
 173   }
 174   glutPostRedisplay();
 175 }
 176
 177 /*  Main Loop
 178  *  Open window with initial window size, title bar,
 179  *  RGBA display mode, and handle input events.
 180  */
 181 int main(int argc, char** argv)
 182 {
 183     glutInit(&argc, argv);
 184     glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_STENCIL);
 185     glutInitWindowSize (400, 400);
 186     glutCreateWindow (argv[0]);
 187     myinit ();
 188     glutReshapeFunc (myReshape);
 189     glutDisplayFunc(display);
 190     glutKeyboardFunc(key);
 191     glutMainLoop();
 192     return 0;             /* ANSI C requires main to return int. */
 193 }