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1 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> |
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3 | <?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>glLightModel</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glLightModel"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glLightModel — set the lighting model parameters</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glLightModelf</b>(</code></td><td>GLenum </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfloat </td><td><var class="pdparam">param</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glLightModeli</b>(</code></td><td>GLenum </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLint </td><td><var class="pdparam">param</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>pname</code></em></span></dt><dd><p> | |
4 | Specifies a single-valued lighting model parameter. | |
5 | <code class="constant">GL_LIGHT_MODEL_LOCAL_VIEWER</code>, | |
6 | <code class="constant">GL_LIGHT_MODEL_COLOR_CONTROL</code>, and | |
7 | <code class="constant">GL_LIGHT_MODEL_TWO_SIDE</code> are accepted. | |
8 | </p></dd><dt><span class="term"><em class="parameter"><code>param</code></em></span></dt><dd><p> | |
9 | Specifies the value that <em class="parameter"><code>param</code></em> will be set to. | |
10 | </p></dd></dl></div></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glLightModelfv</b>(</code></td><td>GLenum </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>const GLfloat * </td><td><var class="pdparam">params</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glLightModeliv</b>(</code></td><td>GLenum </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>const GLint * </td><td><var class="pdparam">params</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters2"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>pname</code></em></span></dt><dd><p> | |
11 | Specifies a lighting model parameter. | |
12 | <code class="constant">GL_LIGHT_MODEL_AMBIENT</code>, | |
13 | <code class="constant">GL_LIGHT_MODEL_COLOR_CONTROL</code>, | |
14 | <code class="constant">GL_LIGHT_MODEL_LOCAL_VIEWER</code>, and | |
15 | <code class="constant">GL_LIGHT_MODEL_TWO_SIDE</code> are accepted. | |
16 | </p></dd><dt><span class="term"><em class="parameter"><code>params</code></em></span></dt><dd><p> | |
17 | Specifies a pointer to the value or values that <em class="parameter"><code>params</code></em> will be set to. | |
18 | </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> | |
19 | <code class="function">glLightModel</code> sets the lighting model parameter. | |
20 | <em class="parameter"><code>pname</code></em> names a parameter and <em class="parameter"><code>params</code></em> gives the new value. | |
21 | There are three lighting model parameters: | |
22 | </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_LIGHT_MODEL_AMBIENT</code></span></dt><dd><p> | |
23 | </p><p> | |
24 | <em class="parameter"><code>params</code></em> contains four integer or floating-point values that specify | |
25 | the ambient RGBA intensity of the entire scene. | |
26 | Integer values are mapped linearly such that the most positive representable | |
27 | value maps to 1.0, | |
28 | and the most negative representable value maps to | |
29 | <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> | |
30 | ||
31 | <mml:mn>-1.0</mml:mn> | |
32 | </mml:math>. | |
33 | Floating-point values are mapped directly. | |
34 | Neither integer nor floating-point values are clamped. | |
35 | The initial ambient scene intensity is (0.2, 0.2, 0.2, 1.0). | |
36 | </p></dd><dt><span class="term"><code class="constant">GL_LIGHT_MODEL_COLOR_CONTROL</code></span></dt><dd><p> | |
37 | </p><p> | |
38 | <em class="parameter"><code>params</code></em> must be either <code class="constant">GL_SEPARATE_SPECULAR_COLOR</code> or | |
39 | <code class="constant">GL_SINGLE_COLOR</code>. | |
40 | <code class="constant">GL_SINGLE_COLOR</code> specifies that a single color is generated from the | |
41 | lighting computation for a vertex. <code class="constant">GL_SEPARATE_SPECULAR_COLOR</code> | |
42 | specifies that the specular color computation of lighting be stored | |
43 | separately from the remainder of the lighting computation. The specular | |
44 | color is summed into the generated fragment's color after the application | |
45 | of texture mapping (if enabled). The initial value is <code class="constant">GL_SINGLE_COLOR</code>. | |
46 | </p></dd><dt><span class="term"><code class="constant">GL_LIGHT_MODEL_LOCAL_VIEWER</code></span></dt><dd><p> | |
47 | </p><p> | |
48 | <em class="parameter"><code>params</code></em> is a single integer or floating-point value that specifies | |
49 | how specular reflection angles are computed. | |
50 | If <em class="parameter"><code>params</code></em> is 0 (or 0.0), specular reflection angles take the | |
51 | view direction to be parallel to and in the direction of the -<span class="emphasis"><em>z</em></span> axis, | |
52 | regardless of the location of the vertex in eye coordinates. | |
53 | Otherwise, specular reflections are computed from the origin | |
54 | of the eye coordinate system. | |
55 | The initial value is 0. | |
56 | </p></dd><dt><span class="term"><code class="constant">GL_LIGHT_MODEL_TWO_SIDE</code></span></dt><dd><p> | |
57 | </p><p> | |
58 | <em class="parameter"><code>params</code></em> is a single integer or floating-point value that specifies | |
59 | whether one- or two-sided lighting calculations are done for polygons. | |
60 | It has no effect on the lighting calculations for points, | |
61 | lines, | |
62 | or bitmaps. | |
63 | If <em class="parameter"><code>params</code></em> is 0 (or 0.0), one-sided lighting is specified, | |
64 | and only the <span class="emphasis"><em>front</em></span> material parameters are used in the | |
65 | lighting equation. | |
66 | Otherwise, two-sided lighting is specified. | |
67 | In this case, vertices of back-facing polygons are lighted using the | |
68 | <span class="emphasis"><em>back</em></span> material parameters | |
69 | and have their normals reversed before the lighting equation is evaluated. | |
70 | Vertices of front-facing polygons are always lighted using the | |
71 | <span class="emphasis"><em>front</em></span> material parameters, | |
72 | with no change to their normals. The initial value is 0. | |
73 | </p></dd></dl></div><p> | |
74 | In RGBA mode, the lighted color of a vertex is the sum of | |
75 | the material emission intensity, | |
76 | the product of the material ambient reflectance and the lighting model full-scene | |
77 | ambient intensity, | |
78 | and the contribution of each enabled light source. | |
79 | Each light source contributes the sum of three terms: | |
80 | ambient, diffuse, and specular. | |
81 | The ambient light source contribution is the product of the material ambient | |
82 | reflectance and the light's ambient intensity. | |
83 | The diffuse light source contribution is the product of the material diffuse | |
84 | reflectance, | |
85 | the light's diffuse intensity, | |
86 | and the dot product of the vertex's normal with the normalized vector from | |
87 | the vertex to the light source. | |
88 | The specular light source contribution is the product of the material specular | |
89 | reflectance, | |
90 | the light's specular intensity, | |
91 | and the dot product of the normalized vertex-to-eye and vertex-to-light | |
92 | vectors, | |
93 | raised to the power of the shininess of the material. | |
94 | All three light source contributions are attenuated equally based on | |
95 | the distance from the vertex to the light source and on light source | |
96 | direction, spread exponent, and spread cutoff angle. | |
97 | All dot products are replaced with 0 if they evaluate to a negative value. | |
98 | </p><p> | |
99 | The alpha component of the resulting lighted color is set to the alpha value | |
100 | of the material diffuse reflectance. | |
101 | </p><p> | |
102 | In color index mode, | |
103 | the value of the lighted index of a vertex ranges from the ambient | |
104 | to the specular values passed to <a class="citerefentry" href="glMaterial.xml"><span class="citerefentry"><span class="refentrytitle">glMaterial</span></span></a> using <code class="constant">GL_COLOR_INDEXES</code>. | |
105 | Diffuse and specular coefficients, | |
106 | computed with a (.30, .59, .11) weighting of the lights' colors, | |
107 | the shininess of the material, | |
108 | and the same reflection and attenuation equations as in the RGBA case, | |
109 | determine how much above ambient the resulting index is. | |
110 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p> | |
111 | <code class="constant">GL_LIGHT_MODEL_COLOR_CONTROL</code> is available only if the GL version is | |
112 | 1.2 or greater. | |
113 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p> | |
114 | <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>pname</code></em> is not an accepted value. | |
115 | </p><p> | |
116 | <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>pname</code></em> is | |
117 | <code class="constant">GL_LIGHT_MODEL_COLOR_CONTROL</code> and <em class="parameter"><code>params</code></em> is not one of | |
118 | <code class="constant">GL_SINGLE_COLOR</code> or <code class="constant">GL_SEPARATE_SPECULAR_COLOR</code>. | |
119 | </p><p> | |
120 | <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glLightModel</code> is executed between | |
121 | the execution of <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a> and the corresponding execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>. | |
122 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p> | |
123 | <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_LIGHT_MODEL_AMBIENT</code> | |
124 | </p><p> | |
125 | <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_LIGHT_MODEL_COLOR_CONTROL</code> | |
126 | </p><p> | |
127 | <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_LIGHT_MODEL_LOCAL_VIEWER</code> | |
128 | </p><p> | |
129 | <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_LIGHT_MODEL_TWO_SIDE</code> | |
130 | </p><p> | |
131 | <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_LIGHTING</code> | |
132 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> | |
133 | <a class="citerefentry" href="glLight.xml"><span class="citerefentry"><span class="refentrytitle">glLight</span></span></a>, | |
134 | <a class="citerefentry" href="glMaterial.xml"><span class="citerefentry"><span class="refentrytitle">glMaterial</span></span></a> | |
135 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
136 | Copyright <span class="trademark"></span>© 1991-2006 | |
137 | Silicon Graphics, Inc. This document is licensed under the SGI | |
138 | Free Software B License. For details, see | |
139 | <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>. | |
140 | </p></div></div></body></html> |