1GLLIGHTMODEL(3G) GLLIGHTMODEL(3G)
2
6 glLightModelf, glLightModeli, glLightModelfv, glLightModeliv - set the
7 lighting model parameters
8
11 void glLightModelf( GLenum pname,
12 GLfloat param )
13 void glLightModeli( GLenum pname,
14 GLint param )
15
18 pname Specifies a single-valued lighting model parameter.
19 GL_LIGHT_MODEL_LOCAL_VIEWER, GL_LIGHT_MODEL_COLOR_CONTROL, and
20 GL_LIGHT_MODEL_TWO_SIDE are accepted.
21 param Specifies the value that param will be set to.
23
25 void glLightModelfv( GLenum pname,
26 const GLfloat *params )
27 void glLightModeliv( GLenum pname,
28 const GLint *params )
29
32 pname Specifies a lighting model parameter. GL_LIGHT_MODEL_AMBIENT,
33 GL_LIGHT_MODEL_COLOR_CONTROL, GL_LIGHT_MODEL_LOCAL_VIEWER, and
34 GL_LIGHT_MODEL_TWO_SIDE are accepted.
35 params Specifies a pointer to the value or values that params will be
37 set to.
38
40 glLightModel sets the lighting model parameter. pname names a parame‐
41 ter and params gives the new value. There are three lighting model
42 parameters:
43 GL_LIGHT_MODEL_AMBIENT
45 params contains four integer or floating-point values that
46 specify the ambient RGBA intensity of the entire scene.
47 Integer values are mapped linearly such that the most posi‐
48 tive representable value maps to 1.0, and the most negative
49 representable value maps to -1.0. Floating-point values are
50 mapped directly. Neither integer nor floating-point values
51 are clamped. The initial ambient scene intensity is (0.2,
52 0.2, 0.2, 1.0).
53 GL_LIGHT_MODEL_COLOR_CONTROL
55 params must be either GL_SEPARATE_SPECULAR_COLOR or
56 GL_SINGLE_COLOR. GL_SINGLE_COLOR specifies that a single
57 color is generated from the lighting computation for a ver‐
58 tex. GL_SEPARATE_SPECULAR_COLOR specifies that the specular
59 color computation of lighting be stored separately from the
60 remainder of the lighting computation. The specular color is
61 summed into the generated fragment's color after the applica‐
62 tion of texture mapping (if enabled). The initial value is
63 GL_SINGLE_COLOR.
64 GL_LIGHT_MODEL_LOCAL_VIEWER
66 params is a single integer or floating-point value that spec‐
67 ifies how specular reflection angles are computed. If params
68 is 0 (or 0.0), specular reflection angles take the view
69 direction to be parallel to and in the direction of the -z
70 axis, regardless of the location of the vertex in eye coordi‐
71 nates. Otherwise, specular reflections are computed from the
72 origin of the eye coordinate system. The initial value is 0.
73 GL_LIGHT_MODEL_TWO_SIDE
75 params is a single integer or floating-point value that spec‐
76 ifies whether one- or two-sided lighting calculations are
77 done for polygons. It has no effect on the lighting calcula‐
78 tions for points, lines, or bitmaps. If params is 0 (or
79 0.0), one-sided lighting is specified, and only the front
80 material parameters are used in the lighting equation. Oth‐
81 erwise, two-sided lighting is specified. In this case, ver‐
82 tices of back-facing polygons are lighted using the back
83 material parameters, and have their normals reversed before
84 the lighting equation is evaluated. Vertices of front-facing
85 polygons are always lighted using the front material parame‐
86 ters, with no change to their normals. The initial value is
87 0.
88 In RGBA mode, the lighted color of a vertex is the sum of the material
90 emission intensity, the product of the material ambient reflectance and
91 the lighting model full-scene ambient intensity, and the contribution
92 of each enabled light source. Each light source contributes the sum of
93 three terms: ambient, diffuse, and specular. The ambient light source
94 contribution is the product of the material ambient reflectance and the
95 light's ambient intensity. The diffuse light source contribution is
96 the product of the material diffuse reflectance, the light's diffuse
97 intensity, and the dot product of the vertex's normal with the normal‐
98 ized vector from the vertex to the light source. The specular light
99 source contribution is the product of the material specular
100 reflectance, the light's specular intensity, and the dot product of the
101 normalized vertex-to-eye and vertex-to-light vectors, raised to the
102 power of the shininess of the material. All three light source contri‐
103 butions are attenuated equally based on the distance from the vertex to
104 the light source and on light source direction, spread exponent, and
105 spread cutoff angle. All dot products are replaced with 0 if they
106 evaluate to a negative value.
107 The alpha component of the resulting lighted color is set to the alpha
109 value of the material diffuse reflectance.
110 In color index mode, the value of the lighted index of a vertex ranges
112 from the ambient to the specular values passed to glMaterial using
113 GL_COLOR_INDEXES. Diffuse and specular coefficients, computed with a
114 (.30, .59, .11) weighting of the lights' colors, the shininess of the
115 material, and the same reflection and attenuation equations as in the
116 RGBA case, determine how much above ambient the resulting index is.
117
119 GL_LIGHT_MODEL_COLOR_CONTROL is available only if the GL version is 1.2
120 or greater.
121
123 GL_INVALID_ENUM is generated if pname is not an accepted value.
124 GL_INVALID_ENUM is generated if pname is GL_LIGHT_MODEL_COLOR_CONTROL
126 and params is not one of GL_SINGLE_COLOR or GL_SEPARATE_SPECULAR_COLOR.
127 GL_INVALID_OPERATION is generated if glLightModel is executed between
129 the execution of glBegin and the corresponding execution of glEnd.
130
132 glGet with argument GL_LIGHT_MODEL_AMBIENT
133 glGet with argument GL_LIGHT_MODEL_COLOR_CONTROL
134 glGet with argument GL_LIGHT_MODEL_LOCAL_VIEWER
135 glGet with argument GL_LIGHT_MODEL_TWO_SIDE
136 glIsEnabled with argument GL_LIGHTING
137
139 glLight(3G), glMaterial(3G)
140 GLLIGHTMODEL(3G)