1GLLIGHTMODEL(3G)                 OpenGL Manual                GLLIGHTMODEL(3G)
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NAME

6       glLightModel - set the lighting model parameters
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C SPECIFICATION

9       void glLightModelf(GLenum pname, GLfloat param);
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11       void glLightModeli(GLenum pname, GLint param);
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PARAMETERS

14       pname
15           Specifies a single-valued lighting model parameter.
16           GL_LIGHT_MODEL_LOCAL_VIEWER, GL_LIGHT_MODEL_COLOR_CONTROL, and
17           GL_LIGHT_MODEL_TWO_SIDE are accepted.
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19       param
20           Specifies the value that param will be set to.
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C SPECIFICATION

23       void glLightModelfv(GLenum pname, const GLfloat * params);
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25       void glLightModeliv(GLenum pname, const GLint * params);
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PARAMETERS

28       pname
29           Specifies a lighting model parameter.  GL_LIGHT_MODEL_AMBIENT,
30           GL_LIGHT_MODEL_COLOR_CONTROL, GL_LIGHT_MODEL_LOCAL_VIEWER, and
31           GL_LIGHT_MODEL_TWO_SIDE are accepted.
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33       params
34           Specifies a pointer to the value or values that params will be set
35           to.
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DESCRIPTION

38       glLightModel sets the lighting model parameter.  pname names a
39       parameter and params gives the new value. There are three lighting
40       model parameters:
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42       GL_LIGHT_MODEL_AMBIENT
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44           params contains four integer or floating-point values that specify
45           the ambient RGBA intensity of the entire scene. Integer values are
46           mapped linearly such that the most positive representable value
47           maps to 1.0, and the most negative representable value maps to
48           -1.0. Floating-point values are mapped directly. Neither integer
49           nor floating-point values are clamped. The initial ambient scene
50           intensity is (0.2, 0.2, 0.2, 1.0).
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52       GL_LIGHT_MODEL_COLOR_CONTROL
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54           params must be either GL_SEPARATE_SPECULAR_COLOR or
55           GL_SINGLE_COLOR.  GL_SINGLE_COLOR specifies that a single color is
56           generated from the lighting computation for a vertex.
57           GL_SEPARATE_SPECULAR_COLOR specifies that the specular color
58           computation of lighting be stored separately from the remainder of
59           the lighting computation. The specular color is summed into the
60           generated fragment's color after the application of texture mapping
61           (if enabled). The initial value is GL_SINGLE_COLOR.
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63       GL_LIGHT_MODEL_LOCAL_VIEWER
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65           params is a single integer or floating-point value that specifies
66           how specular reflection angles are computed. If params is 0 (or
67           0.0), specular reflection angles take the view direction to be
68           parallel to and in the direction of the -z axis, regardless of the
69           location of the vertex in eye coordinates. Otherwise, specular
70           reflections are computed from the origin of the eye coordinate
71           system. The initial value is 0.
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73       GL_LIGHT_MODEL_TWO_SIDE
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75           params is a single integer or floating-point value that specifies
76           whether one- or two-sided lighting calculations are done for
77           polygons. It has no effect on the lighting calculations for points,
78           lines, or bitmaps. If params is 0 (or 0.0), one-sided lighting is
79           specified, and only the front material parameters are used in the
80           lighting equation. Otherwise, two-sided lighting is specified. In
81           this case, vertices of back-facing polygons are lighted using the
82           back material parameters and have their normals reversed before the
83           lighting equation is evaluated. Vertices of front-facing polygons
84           are always lighted using the front material parameters, with no
85           change to their normals. The initial value is 0.
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87       In RGBA mode, the lighted color of a vertex is the sum of the material
88       emission intensity, the product of the material ambient reflectance and
89       the lighting model full-scene ambient intensity, and the contribution
90       of each enabled light source. Each light source contributes the sum of
91       three terms: ambient, diffuse, and specular. The ambient light source
92       contribution is the product of the material ambient reflectance and the
93       light's ambient intensity. The diffuse light source contribution is the
94       product of the material diffuse reflectance, the light's diffuse
95       intensity, and the dot product of the vertex's normal with the
96       normalized vector from the vertex to the light source. The specular
97       light source contribution is the product of the material specular
98       reflectance, the light's specular intensity, and the dot product of the
99       normalized vertex-to-eye and vertex-to-light vectors, raised to the
100       power of the shininess of the material. All three light source
101       contributions are attenuated equally based on the distance from the
102       vertex to the light source and on light source direction, spread
103       exponent, and spread cutoff angle. All dot products are replaced with 0
104       if they evaluate to a negative value.
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106       The alpha component of the resulting lighted color is set to the alpha
107       value of the material diffuse reflectance.
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109       In color index mode, the value of the lighted index of a vertex ranges
110       from the ambient to the specular values passed to glMaterial() using
111       GL_COLOR_INDEXES. Diffuse and specular coefficients, computed with a
112       (.30, .59, .11) weighting of the lights' colors, the shininess of the
113       material, and the same reflection and attenuation equations as in the
114       RGBA case, determine how much above ambient the resulting index is.
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NOTES

117       GL_LIGHT_MODEL_COLOR_CONTROL is available only if the GL version is 1.2
118       or greater.
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ERRORS

121       GL_INVALID_ENUM is generated if pname is not an accepted value.
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123       GL_INVALID_ENUM is generated if pname is GL_LIGHT_MODEL_COLOR_CONTROL
124       and params is not one of GL_SINGLE_COLOR or GL_SEPARATE_SPECULAR_COLOR.
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126       GL_INVALID_OPERATION is generated if glLightModel is executed between
127       the execution of glBegin() and the corresponding execution of glEnd().
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ASSOCIATED GETS

130       glGet() with argument GL_LIGHT_MODEL_AMBIENT
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132       glGet() with argument GL_LIGHT_MODEL_COLOR_CONTROL
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134       glGet() with argument GL_LIGHT_MODEL_LOCAL_VIEWER
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136       glGet() with argument GL_LIGHT_MODEL_TWO_SIDE
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138       glIsEnabled() with argument GL_LIGHTING
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SEE ALSO

141       glLight(), glMaterial()
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144       Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
145       under the SGI Free Software B License. For details, see
146       http://oss.sgi.com/projects/FreeB/.
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AUTHORS

149       opengl.org
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153opengl.org                        07/13/2018                  GLLIGHTMODEL(3G)
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