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
124
|
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en">
<head>
<title>GAMGI Tutorials: Directional and positional lights</title>
<link rel="icon" type="image/png" href="../icon/gamgi16.png"/>
<link rel="stylesheet" type="text/css" href="../css/base.css"/>
<link rel="stylesheet" type="text/css" href="../css/notebook.css"/>
</head>
<body>
<h1>Directional and positional lights</h1>
<div id="notebook">
<ul>
<li><span>Page 1</span></li>
<li><a href="lights_page2.html">Page 2</a></li>
</ul>
</div>
<div class="contents">
We demonstrate here the three types of lights that GAMGI
(and OpenGL) supports, plus other illumination issues.
First we create an atom with a large curved surface, that we will
use as a target, then we create the various lights and point them
to the surface.
<h3>Directional light</h3>
<ol>
<li>
Press <b>Atom->Create</b> and set <b>Element</b> to <b>O</b>,
<b>Position</b> to <b>(0.0, 0.0, 0.0)</b>, <b>Style</b> to
<b>Solid</b> and <b>Scale</b> to <b>15.0</b>.
After pressing <b>Ok</b>, a large sphere representing the new atom
becomes visible, seen as a circle because tridimensional effects cannot
be seen in the absence of diffuse and specular light components.
</li>
<li>
Press <b>Light->Create</b> and set color <b>Ambient</b> (<b>Color</b> page)
to <b>(0.0, 0.0, 0.0)</b>, and <b>Diffuse</b> to <b>(0.8, 0.8, 0.8)</b>.
After pressing <b>Ok</b>, a default <b>Directional</b> light is created,
illuminating the atom sphere, whose shape is now clearly visible.
</li>
<li>
To select the light, either: 1) press the mouse middle button over the top
menu where it says <b>Light</b>, and then press the mouse over the drawing
area; or 2) press <b>Light->Select</b>, to open the dialog to select lights,
and then press the mouse over the drawing area. In both cases, a menu pops up,
showing one menu item, for the only light available. After choosing this light,
it becomes the selected object.
</li>
<li>
Press the left button and dragg the mouse to rotate the light direction,
exactly as if rotating a molecule.
</li>
</ol>
<h3>Positional light</h3>
<ol>
<li>
Press <b>Light->Modify</b> and press the mouse over the drawing area. A menu
pops up, showing one menu item, for the only light available. After choosing
this light, confirm its properties and then set <b>Light</b> to <b>Positional</b>.
After pressing <b>Ok</b>, the light becomes positional, with the new parameters.
</li>
<li>
Press the middle button and dragg the mouse to move the light position,
exactly as if moving a molecule.
</li>
</ol>
<h3>Spot light</h3>
<ol>
<li>
Press <b>Light->Modify</b> and press the mouse over the graphic area.
A menu pops up, showing one menu item, for the only light available.
After choosing this light, confirm its properties, in particular
the new light position, that was changed with the mouse.
</li>
<li>
Set <b>Light</b> to <b>Spot</b> and <b>Angle</b> to <b>10.0</b>.
After pressing <b>Ok</b>, the light becomes a spot, with the new
parameters. Because the beam angle cutoff is only 10 degrees and
the light is only 10 length units away, only the central part of
the atom sphere is illuminated (setting angle to 1.0 emulates a laser).
</li>
<li>
Press <b>Light->Create</b> and set color <b>Ambient</b> to <b>(0.4, 0.4, 0.4)</b>
and <b>Diffuse</b> to <b>(0.0, 0.0, 0.0)</b>. After pressing <b>Ok</b>,
a second light is created, and its weak ambient light illuminates the
whole atom as a halo. The selected object is still the first light.
</li>
<li>
Press the left button and dragg the mouse to rotate the light direction,
exactly as if rotating a molecule. Press the middle button and dragg the
mouse to move the light position, exactly as if moving a molecule. Press
the right button and dragg the mouse to increase or decrease the angle
cutoff, exactly as if scaling a molecule.
</li>
</ol>
</div>
<div id="bottom">
<a href="../index.shtml">Home</a>
</div>
</body>
</html>
|
