summaryrefslogtreecommitdiff
path: root/manuals/chickadee/Lights.html
blob: 4ae75ffc512500602bca4c626d02b4a7b144e4ae (plain)
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
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!--  Copyright (C) 2017-2023  David Thompson dthompson2@worcester.edu

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
A copy of the license is included in the section entitled "GNU
Free Documentation License".

A copy of the license is also available from the Free Software
Foundation Web site at http://www.gnu.org/licenses/fdl.html.


* Chickadee: (chickadee).     Game programming toolkit for Guile.

The document was typeset with
http://www.texinfo.org/ (GNU Texinfo).
  -->
<!--  Created by GNU Texinfo 6.7, http://www.gnu.org/software/texinfo/  -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Lights (The Chickadee Game Toolkit)</title>

<meta name="description" content="Lights (The Chickadee Game Toolkit)" />
<meta name="keywords" content="Lights (The Chickadee Game Toolkit)" />
<meta name="resource-type" content="document" />
<meta name="distribution" content="global" />
<meta name="Generator" content="makeinfo" />
<link href="index.html" rel="start" title="Top" />
<link href="Index.html" rel="index" title="Index" />
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents" />
<link href="Graphics.html" rel="up" title="Graphics" />
<link href="Skyboxes.html" rel="next" title="Skyboxes" />
<link href="Models.html" rel="prev" title="Models" />
<style type="text/css">
&lt;!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
@media (min-width: 1140px) {
    body {
        margin-left: 14rem;
        margin-right: 4rem;
        max-width: 52rem;
    }
}

@media (min-width: 800px) and (max-width: 1140px) {
    body {
        margin-left: 6rem;
        margin-right: 4rem;
        max-width: 52rem;
    }
}

@media (max-width: 800px) {
    body {
        margin: 1rem;
    }
}

--&gt;
</style>
<link rel="stylesheet" type="text/css" href="https://dthompson.us/css/dthompson.css" />


</head>

<body lang="en">
<span id="Lights"></span><div class="header">
<p>
Next: <a href="Skyboxes.html" accesskey="n" rel="next">Skyboxes</a>, Previous: <a href="Models.html" accesskey="p" rel="prev">Models</a>, Up: <a href="Graphics.html" accesskey="u" rel="up">Graphics</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr />
<span id="Lights-1"></span><h4 class="subsection">5.3.9 Lights</h4>

<p>The <code>(chickadee graphics light)</code> module provides a data type for
dynamic lights that can be used to light 3D objects (such as
<a href="Models.html">Models</a> or <a href="Meshes.html">Meshes</a>.)
</p>
<p>There are 3 types of dynamic lights:
</p>
<ul>
<li> point light:
Emits light in all directions from a specific point in space, like a
light bulb.
</li><li> directional light:
Emits light of a constant intensity in a direction, like sunlight.
</li><li> spot light:
Emits a cone of light in a direction, like a flashlight.
</li></ul>

<dl>
<dt id="index-make_002dpoint_002dlight">Procedure: <strong>make-point-light</strong> <em>[#:position (vec3 0 0 0)] [#:color black]        [#:intensity 1]</em></dt>
<dd>
<p>Return a new point light located at <var>position</var> that emits
<var>color</var> light.
</p></dd></dl>

<dl>
<dt id="index-make_002ddirectional_002dlight">Procedure: <strong>make-directional-light</strong> <em>[#:direction (vec3 0 -1 0)]        [#:color black] [#:intensity 1]</em></dt>
<dd>
<p>Return a new directional light that emits <var>color</var> light in
<var>direction</var>.
</p></dd></dl>

<dl>
<dt id="index-make_002dspot_002dlight">Procedure: <strong>make-spot-light</strong> <em>[#:position (vec3 0 0 0)]        [#:direction (vec3 0 -1 0)] [#:color black] [#:cut-off <em>π/4</em>]        [#:intensity 1]</em></dt>
<dd>
<p>Return a new spot light located at <var>position</var> that emits
<var>color</var> light in <var>direction</var> in a cone that cuts off at
<var>cut-off</var> radians.
</p></dd></dl>

<dl>
<dt id="index-point_002dlight_003f">Procedure: <strong>point-light?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a point light.
</p></dd></dl>

<dl>
<dt id="index-directional_002dlight_003f">Procedure: <strong>directional-light?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a directional light.
</p></dd></dl>

<dl>
<dt id="index-spot_002dlight_003f">Procedure: <strong>spot-light?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a spot light.
</p></dd></dl>

<dl>
<dt id="index-light_002dtype">Procedure: <strong>light-type</strong> <em>light</em></dt>
<dd><p>Return the type of <var>light</var>, one of:
</p>
<ul>
<li> point
</li><li> directional
</li><li> spot
</li></ul>

</dd></dl>

<dl>
<dt id="index-light_002dcolor">Procedure: <strong>light-color</strong> <em>light</em></dt>
<dd><p>Return the color of <var>light</var>.
</p></dd></dl>

<dl>
<dt id="index-light_002dintensity">Procedure: <strong>light-intensity</strong> <em>light</em></dt>
<dd><p>Return the intensity of <var>light</var>.
</p></dd></dl>

<dl>
<dt id="index-light_002dposition">Procedure: <strong>light-position</strong> <em>light</em></dt>
<dd><p>Return the position of <var>light</var>.  The value is irrelevant for
directional lights.
</p></dd></dl>

<dl>
<dt id="index-light_002ddirection">Procedure: <strong>light-direction</strong> <em>light</em></dt>
<dd><p>Return the direction of <var>light</var>.  The value is irrelevant for
point lights.
</p></dd></dl>

<dl>
<dt id="index-light_002dcut_002doff">Procedure: <strong>light-cut-off</strong> <em>light</em></dt>
<dd><p>Return the cosine of the cut off angle of <var>light</var>.  The value is
only relevant for spot lights.
</p></dd></dl>

<dl>
<dt id="index-set_002dlight_002dcolor_0021">Procedure: <strong>set-light-color!</strong> <em>light color</em></dt>
<dd><p>Set the color of <var>light</var> to <var>color</var>.
</p></dd></dl>

<dl>
<dt id="index-set_002dlight_002dposition_0021">Procedure: <strong>set-light-position!</strong> <em>light position</em></dt>
<dd><p>Set the position of <var>light</var> to <var>position</var>.
</p></dd></dl>

<dl>
<dt id="index-set_002dlight_002ddirection_0021">Procedure: <strong>set-light-direction!</strong> <em>light direction</em></dt>
<dd><p>Set the direction of <var>light</var> to <var>direction</var>.
</p></dd></dl>

<dl>
<dt id="index-set_002dlight_002dcut_002doff_0021">Procedure: <strong>set-light-cut-off!</strong> <em>light cut-off</em></dt>
<dd><p>Set the cut off angle of <var>light</var> to <var>cut-off</var>.
</p></dd></dl>

<hr />
<div class="header">
<p>
Next: <a href="Skyboxes.html" accesskey="n" rel="next">Skyboxes</a>, Previous: <a href="Models.html" accesskey="p" rel="prev">Models</a>, Up: <a href="Graphics.html" accesskey="u" rel="up">Graphics</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p>
</div>



</body>
</html>