2 * Copyright (c) 1993-1997, Silicon Graphics, Inc.
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.
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.
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31 * Unpublished-- rights reserved under the copyright laws of the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.
35 * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
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.
47 static int leftFirst
= GL_TRUE
;
49 /* Initialize alpha blending function.
51 static void init(void)
53 glBlendEquation (GL_FUNC_REVERSE_SUBTRACT
);
54 glBlendFunc (GL_ONE_MINUS_SRC_ALPHA
, GL_SRC_ALPHA
);
55 glShadeModel (GL_FLAT
);
56 glClearColor (1.0, 0.0, 0.0, 0.0);
59 static void drawLeftTriangle(void)
61 /* draw yellow triangle on LHS of screen */
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);
71 static void drawRightTriangle(void)
73 /* draw cyan triangle on RHS of screen */
76 glBegin (GL_TRIANGLES
);
77 glColor4f(0.0, 1.0, 1.0, 0.75);
78 glVertex3f(0.9, 0.9, 0.0);
79 glVertex3f(0.3, 0.5, 0.0);
80 glVertex3f(0.9, 0.1, 0.0);
87 glClear(GL_COLOR_BUFFER_BIT
);
101 void reshape(int w
, int h
)
103 glViewport(0, 0, (GLsizei
) w
, (GLsizei
) h
);
104 glMatrixMode(GL_PROJECTION
);
107 gluOrtho2D (0.0, 1.0, 0.0, 1.0*(GLfloat
)h
/(GLfloat
)w
);
109 gluOrtho2D (0.0, 1.0*(GLfloat
)w
/(GLfloat
)h
, 0.0, 1.0);
113 void keyboard(unsigned char key
, int x
, int y
)
118 leftFirst
= !leftFirst
;
121 case 27: /* Escape key */
130 * Open window with initial window size, title bar,
131 * RGBA display mode, and handle input events.
133 int main(int argc
, char** argv
)
135 glutInit(&argc
, argv
);
136 glutInitDisplayMode (GLUT_SINGLE
| GLUT_RGB
);
137 glutInitWindowSize (200, 200);
138 glutCreateWindow (argv
[0]);
140 glutReshapeFunc (reshape
);
141 glutKeyboardFunc (keyboard
);
142 glutDisplayFunc (display
);