#/* # * 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 # * Unpublished-- rights reserved under the copyright laws of the # * United States.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. # */ require "opengl" require "glut" require "mathn" $leftFirst = GL::TRUE; #/* Initialize alpha blending function. # */ def init GL.Enable(GL::BLEND); GL.BlendFunc(GL::SRC_ALPHA, GL::ONE_MINUS_SRC_ALPHA); GL.ShadeModel(GL::FLAT); GL.ClearColor(0.0, 0.0, 0.0, 0.0); end def drawLeftTriangle #/* draw yellow triangle on LHS of screen */ GL.Begin(GL::TRIANGLES); GL.Color(1.0, 1.0, 0.0, 0.75); GL.Vertex(0.1, 0.9, 0.0); GL.Vertex(0.1, 0.1, 0.0); GL.Vertex(0.7, 0.5, 0.0); GL.End(); end def drawRightTriangle #/* draw cyan triangle on RHS of screen */ GL.Begin(GL::TRIANGLES); GL.Color(0.0, 1.0, 1.0, 0.75); GL.Vertex(0.9, 0.9, 0.0); GL.Vertex(0.3, 0.5, 0.0); GL.Vertex(0.9, 0.1, 0.0); GL.End(); end display = Proc.new { GL.Clear(GL::COLOR_BUFFER_BIT); if ($leftFirst) drawLeftTriangle(); drawRightTriangle(); else drawRightTriangle(); drawLeftTriangle(); end GL.Flush(); } reshape = Proc.new {|w, h| GL.Viewport(0, 0, w, h); GL.MatrixMode(GL::PROJECTION); GL.LoadIdentity(); if (w <= h) GLU.Ortho2D(0.0, 1.0, 0.0, 1.0*h/w); else GLU.Ortho2D(0.0, 1.0*w/h, 0.0, 1.0); end } # /* ARGSUSED1 */ keyboard = Proc.new {|key, x, y| case (key) when 't'[0],'T'[0] $leftFirst = !$leftFirst; GLUT.PostRedisplay(); when 27 # /* Escape key */ exit(0); end } #/* Main Loop # * Open window with initial window size, title bar, # * RGBA display mode, and handle input events. # */ #int main(int argc, char** argv) #{ GLUT.Init GLUT.InitDisplayMode(GLUT::SINGLE | GLUT::RGB); GLUT.InitWindowSize(200, 200); GLUT.CreateWindow($0); init(); GLUT.ReshapeFunc(reshape); GLUT.KeyboardFunc(keyboard); GLUT.DisplayFunc(display); GLUT.MainLoop();