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+
+/* Copyright (c) Mark J. Kilgard, 1994. */
+
+/*
+ * (c) Copyright 1993, Silicon Graphics, Inc.
+ * ALL RIGHTS RESERVED
+ * Permission to use, copy, modify, and distribute this software for
+ * any purpose and without fee is hereby granted, provided that the above
+ * copyright notice appear in all copies and that both the copyright notice
+ * and this permission notice appear in supporting documentation, and that
+ * the name of Silicon Graphics, Inc. not be used in advertising
+ * or publicity pertaining to distribution of the software without specific,
+ * written prior permission.
+ *
+ * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
+ * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
+ * FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SILICON
+ * GRAPHICS, INC. BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
+ * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
+ * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
+ * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
+ * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC. HAS BEEN
+ * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
+ * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * US Government Users Restricted Rights
+ * Use, duplication, or disclosure by the Government is subject to
+ * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
+ * (c)(1)(ii) of the Rights in Technical Data and Computer Software
+ * clause at DFARS 252.227-7013 and/or in similar or successor
+ * clauses in the FAR or the DOD or NASA FAR Supplement.
+ * Unpublished-- rights reserved under the copyright laws of the
+ * United States. Contractor/manufacturer is Silicon Graphics,
+ * Inc., 2011 N. Shoreline Blvd., Mountain View, CA 94039-7311.
+ *
+ * OpenGL(TM) is a trademark of Silicon Graphics, Inc.
+ */
+/* stencil.c
+ * This program draws two rotated tori in a window.
+ * A diamond in the center of the window masks out part
+ * of the scene. Within this mask, a different model
+ * (a sphere) is drawn in a different color.
+ */
+
+/*
+ * !!! NOTE !!!
+ *
+ * This demo is poorly written. The stencil buffer should be
+ * redrawn in display(), not in the myReshape() function.
+ * The reason is if the window gets "damaged" then the stencil buffer
+ * contents will be in an undefined state (myReshape is not called when
+ * a window is damaged and needs to be redrawn). If the stencil buffer
+ * contents are undefined, the results of display() are unpredictable.
+ *
+ * -Brian
+ */
+
+
+#include <stdlib.h>
+#include <GL/glut.h>
+
+#define YELLOWMAT 1
+#define BLUEMAT 2
+
+void myinit (void)
+{
+ GLfloat yellow_diffuse[] = { 0.7, 0.7, 0.0, 1.0 };
+ GLfloat yellow_specular[] = { 1.0, 1.0, 1.0, 1.0 };
+
+ GLfloat blue_diffuse[] = { 0.1, 0.1, 0.7, 1.0 };
+ GLfloat blue_specular[] = { 0.1, 1.0, 1.0, 1.0 };
+
+ GLfloat position_one[] = { 1.0, 1.0, 1.0, 0.0 };
+
+ glNewList(YELLOWMAT, GL_COMPILE);
+ glMaterialfv(GL_FRONT, GL_DIFFUSE, yellow_diffuse);
+ glMaterialfv(GL_FRONT, GL_SPECULAR, yellow_specular);
+ glMaterialf(GL_FRONT, GL_SHININESS, 64.0);
+ glEndList();
+
+ glNewList(BLUEMAT, GL_COMPILE);
+ glMaterialfv(GL_FRONT, GL_DIFFUSE, blue_diffuse);
+ glMaterialfv(GL_FRONT, GL_SPECULAR, blue_specular);
+ glMaterialf(GL_FRONT, GL_SHININESS, 45.0);
+ glEndList();
+
+ glLightfv(GL_LIGHT0, GL_POSITION, position_one);
+
+ glEnable(GL_LIGHT0);
+ glEnable(GL_LIGHTING);
+ glDepthFunc(GL_LESS);
+ glEnable(GL_DEPTH_TEST);
+
+ glClearStencil(0x0);
+ glEnable(GL_STENCIL_TEST);
+
+}
+
+/* Draw a sphere in a diamond-shaped section in the
+ * middle of a window with 2 tori.
+ */
+void display(void)
+{
+ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+ glStencilOp (GL_KEEP, GL_KEEP, GL_KEEP);
+
+/* draw blue sphere where the stencil is 1 */
+ glStencilFunc (GL_EQUAL, 0x1, 0x1);
+ glCallList (BLUEMAT);
+ glutSolidSphere (0.5, 15, 15);
+
+/* draw the tori where the stencil is not 1 */
+ glStencilFunc (GL_NOTEQUAL, 0x1, 0x1);
+ glPushMatrix();
+ glRotatef (45.0, 0.0, 0.0, 1.0);
+ glRotatef (45.0, 0.0, 1.0, 0.0);
+ glCallList (YELLOWMAT);
+ glutSolidTorus (0.275, 0.85, 15, 15);
+ glPushMatrix();
+ glRotatef (90.0, 1.0, 0.0, 0.0);
+ glutSolidTorus (0.275, 0.85, 15, 15);
+ glPopMatrix();
+ glPopMatrix();
+
+ glFlush();
+ glutSwapBuffers();
+}
+
+/* Whenever the window is reshaped, redefine the
+ * coordinate system and redraw the stencil area.
+ */
+void myReshape(int w, int h)
+{
+ glViewport(0, 0, w, h);
+
+ glClear(GL_STENCIL_BUFFER_BIT);
+/* create a diamond shaped stencil area */
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ glOrtho(-3.0, 3.0, -3.0, 3.0, -1.0, 1.0);
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+
+ glStencilFunc (GL_ALWAYS, 0x1, 0x1);
+ glStencilOp (GL_REPLACE, GL_REPLACE, GL_REPLACE);
+ glBegin(GL_QUADS);
+ glVertex3f (-1.0, 0.0, 0.0);
+ glVertex3f (0.0, 1.0, 0.0);
+ glVertex3f (1.0, 0.0, 0.0);
+ glVertex3f (0.0, -1.0, 0.0);
+ glEnd();
+
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ gluPerspective(45.0, (GLfloat) w/(GLfloat) h, 3.0, 7.0);
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+ glTranslatef(0.0, 0.0, -5.0);
+}
+
+static void
+key(unsigned char k, int x, int y)
+{
+ switch (k) {
+ case 27: /* Escape */
+ exit(0);
+ break;
+ default:
+ return;
+ }
+ glutPostRedisplay();
+}
+
+/* Main Loop
+ * Open window with initial window size, title bar,
+ * RGBA display mode, and handle input events.
+ */
+int main(int argc, char** argv)
+{
+ glutInit(&argc, argv);
+ glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_STENCIL);
+ glutInitWindowSize (400, 400);
+ glutCreateWindow (argv[0]);
+ myinit ();
+ glutReshapeFunc (myReshape);
+ glutDisplayFunc(display);
+ glutKeyboardFunc(key);
+ glutMainLoop();
+ return 0; /* ANSI C requires main to return int. */
+}