/* * Copyright (c) 1993-1997, 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 * Unpublished-- rights reserved under the copyright laws of the * United States.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(R) is a registered trademark of Silicon Graphics, Inc. */ /* * alpha.c * This program draws several overlapping filled polygons * to demonstrate the effect order has on alpha blending results. * Use the 't' key to toggle the order of drawing polygons. */ #include <GL/glut.h> #include <stdlib.h> static int leftFirst = GL_TRUE; /* Initialize alpha blending function. */ static void init(void) { glEnable (GL_BLEND); glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glShadeModel (GL_FLAT); glClearColor (0.0, 0.0, 0.0, 0.0); } static void drawLeftTriangle(void) { /* draw yellow triangle on LHS of screen */ glBegin (GL_TRIANGLES); glColor4f(1.0, 1.0, 0.0, 0.75); glVertex3f(0.1, 0.9, 0.0); glVertex3f(0.1, 0.1, 0.0); glVertex3f(0.7, 0.5, 0.0); glEnd(); } static void drawRightTriangle(void) { /* draw cyan triangle on RHS of screen */ glBegin (GL_TRIANGLES); glColor4f(0.0, 1.0, 1.0, 0.75); glVertex3f(0.9, 0.9, 0.0); glVertex3f(0.3, 0.5, 0.0); glVertex3f(0.9, 0.1, 0.0); glEnd(); } static void display(void) { glClear(GL_COLOR_BUFFER_BIT); if (leftFirst) { drawLeftTriangle(); drawRightTriangle(); } else { drawRightTriangle(); drawLeftTriangle(); } glFlush(); } static void reshape(int w, int h) { glViewport(0, 0, (GLsizei) w, (GLsizei) h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); if (w <= h) gluOrtho2D (0.0, 1.0, 0.0, 1.0*(GLfloat)h/(GLfloat)w); else gluOrtho2D (0.0, 1.0*(GLfloat)w/(GLfloat)h, 0.0, 1.0); } /* ARGSUSED1 */ static void keyboard(unsigned char key, int x, int y) { switch (key) { case 't': case 'T': leftFirst = !leftFirst; glutPostRedisplay(); break; case 27: /* Escape key */ exit(0); break; default: break; } } /* 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_SINGLE | GLUT_RGB); glutInitWindowSize (200, 200); glutCreateWindow (argv[0]); init(); glutReshapeFunc (reshape); glutKeyboardFunc (keyboard); glutDisplayFunc (display); glutMainLoop(); return 0; }