1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
|
#
# 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# Unpublished-- rights reserved under the copyright laws of the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 'mathn'
include Gl,Glu,Glut
$leftFirst = GL_TRUE
# Initialize alpha blending function.
def init
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
glShadeModel(GL_FLAT)
glClearColor(0.0, 0.0, 0.0, 0.0)
end
def drawLeftTriangle
# draw yellow triangle on LHS of screen
glBegin(GL_TRIANGLES)
glColor(1.0, 1.0, 0.0, 0.75)
glVertex(0.1, 0.9, 0.0)
glVertex(0.1, 0.1, 0.0)
glVertex(0.7, 0.5, 0.0)
glEnd()
end
def drawRightTriangle
# draw cyan triangle on RHS of screen
glBegin(GL_TRIANGLES)
glColor(0.0, 1.0, 1.0, 0.75)
glVertex(0.9, 0.9, 0.0)
glVertex(0.3, 0.5, 0.0)
glVertex(0.9, 0.1, 0.0)
glEnd()
end
display = Proc.new do
glClear(GL_COLOR_BUFFER_BIT)
if ($leftFirst)
drawLeftTriangle()
drawRightTriangle()
else
drawRightTriangle()
drawLeftTriangle()
end
glutSwapBuffers()
end
reshape = Proc.new do |w, h|
glViewport(0, 0, w, h)
glMatrixMode(GL_PROJECTION)
glLoadIdentity()
if (w <= h)
gluOrtho2D(0.0, 1.0, 0.0, 1.0*h/w)
else
gluOrtho2D(0.0, 1.0*w/h, 0.0, 1.0)
end
end
keyboard = Proc.new do|key, x, y|
case (key)
when ?t,?T
$leftFirst = !$leftFirst
glutPostRedisplay()
when ?\e # Escape key
exit(0)
end
end
# Main Loop
# Open window with initial window size, title bar,
# RGBA display mode, and handle input events.
glutInit
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB)
glutInitWindowSize(500, 500)
glutInitWindowPosition(100, 100)
glutCreateWindow($0)
init()
glutReshapeFunc(reshape)
glutKeyboardFunc(keyboard)
glutDisplayFunc(display)
glutMainLoop()
|
