| jtg | afb833d | 1999-08-19 00:55:39 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 1993-1997, Silicon Graphics, Inc. |
| 3 | * ALL RIGHTS RESERVED |
| 4 | * Permission to use, copy, modify, and distribute this software for |
| 5 | * any purpose and without fee is hereby granted, provided that the above |
| 6 | * copyright notice appear in all copies and that both the copyright notice |
| 7 | * and this permission notice appear in supporting documentation, and that |
| 8 | * the name of Silicon Graphics, Inc. not be used in advertising |
| 9 | * or publicity pertaining to distribution of the software without specific, |
| 10 | * written prior permission. |
| 11 | * |
| 12 | * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS" |
| 13 | * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE, |
| 14 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR |
| 15 | * FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SILICON |
| 16 | * GRAPHICS, INC. BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT, |
| 17 | * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY |
| 18 | * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION, |
| 19 | * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF |
| 20 | * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC. HAS BEEN |
| 21 | * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON |
| 22 | * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE |
| 23 | * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE. |
| 24 | * |
| 25 | * US Government Users Restricted Rights |
| 26 | * Use, duplication, or disclosure by the Government is subject to |
| 27 | * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph |
| 28 | * (c)(1)(ii) of the Rights in Technical Data and Computer Software |
| 29 | * clause at DFARS 252.227-7013 and/or in similar or successor |
| 30 | * clauses in the FAR or the DOD or NASA FAR Supplement. |
| 31 | * Unpublished-- rights reserved under the copyright laws of the |
| 32 | * United States. Contractor/manufacturer is Silicon Graphics, |
| 33 | * Inc., 2011 N. Shoreline Blvd., Mountain View, CA 94039-7311. |
| 34 | * |
| 35 | * OpenGL(R) is a registered trademark of Silicon Graphics, Inc. |
| 36 | */ |
| 37 | |
| 38 | /* |
| 39 | * alpha.c |
| 40 | * This program draws several overlapping filled polygons |
| 41 | * to demonstrate the effect order has on alpha blending results. |
| 42 | * Use the 't' key to toggle the order of drawing polygons. |
| 43 | */ |
| 44 | #include <GL/glut.h> |
| 45 | #include <stdlib.h> |
| 46 | |
| 47 | static int leftFirst = GL_TRUE; |
| 48 | |
| 49 | /* Initialize alpha blending function. |
| 50 | */ |
| 51 | static void init(void) |
| 52 | { |
| 53 | glEnable (GL_BLEND); |
| 54 | glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); |
| 55 | glShadeModel (GL_FLAT); |
| 56 | glClearColor (0.0, 0.0, 0.0, 0.0); |
| 57 | } |
| 58 | |
| 59 | static void drawLeftTriangle(void) |
| 60 | { |
| 61 | /* draw yellow triangle on LHS of screen */ |
| 62 | |
| 63 | glBegin (GL_TRIANGLES); |
| 64 | glColor4f(1.0, 1.0, 0.0, 0.75); |
| 65 | glVertex3f(0.1, 0.9, 0.0); |
| 66 | glVertex3f(0.1, 0.1, 0.0); |
| 67 | glVertex3f(0.7, 0.5, 0.0); |
| 68 | glEnd(); |
| 69 | } |
| 70 | |
| 71 | static void drawRightTriangle(void) |
| 72 | { |
| 73 | /* draw cyan triangle on RHS of screen */ |
| 74 | |
| 75 | glBegin (GL_TRIANGLES); |
| 76 | glColor4f(0.0, 1.0, 1.0, 0.75); |
| 77 | glVertex3f(0.9, 0.9, 0.0); |
| 78 | glVertex3f(0.3, 0.5, 0.0); |
| 79 | glVertex3f(0.9, 0.1, 0.0); |
| 80 | glEnd(); |
| 81 | } |
| 82 | |
| 83 | void display(void) |
| 84 | { |
| 85 | glClear(GL_COLOR_BUFFER_BIT); |
| 86 | |
| 87 | if (leftFirst) { |
| 88 | drawLeftTriangle(); |
| 89 | drawRightTriangle(); |
| 90 | } |
| 91 | else { |
| 92 | drawRightTriangle(); |
| 93 | drawLeftTriangle(); |
| 94 | } |
| 95 | |
| 96 | glFlush(); |
| 97 | } |
| 98 | |
| 99 | void reshape(int w, int h) |
| 100 | { |
| 101 | glViewport(0, 0, (GLsizei) w, (GLsizei) h); |
| 102 | glMatrixMode(GL_PROJECTION); |
| 103 | glLoadIdentity(); |
| 104 | if (w <= h) |
| 105 | gluOrtho2D (0.0, 1.0, 0.0, 1.0*(GLfloat)h/(GLfloat)w); |
| 106 | else |
| 107 | gluOrtho2D (0.0, 1.0*(GLfloat)w/(GLfloat)h, 0.0, 1.0); |
| 108 | } |
| 109 | |
| 110 | /* ARGSUSED1 */ |
| 111 | void keyboard(unsigned char key, int x, int y) |
| 112 | { |
| 113 | switch (key) { |
| 114 | case 't': |
| 115 | case 'T': |
| 116 | leftFirst = !leftFirst; |
| 117 | glutPostRedisplay(); |
| 118 | break; |
| 119 | case 27: /* Escape key */ |
| 120 | exit(0); |
| 121 | break; |
| 122 | default: |
| 123 | break; |
| 124 | } |
| 125 | } |
| 126 | |
| 127 | /* Main Loop |
| 128 | * Open window with initial window size, title bar, |
| 129 | * RGBA display mode, and handle input events. |
| 130 | */ |
| 131 | int main(int argc, char** argv) |
| 132 | { |
| 133 | glutInit(&argc, argv); |
| 134 | glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); |
| 135 | glutInitWindowSize (200, 200); |
| 136 | glutCreateWindow (argv[0]); |
| 137 | init(); |
| 138 | glutReshapeFunc (reshape); |
| 139 | glutKeyboardFunc (keyboard); |
| 140 | glutDisplayFunc (display); |
| 141 | glutMainLoop(); |
| 142 | return 0; |
| 143 | } |