1GLGETLIGHT(3G) OpenGL Manual GLGETLIGHT(3G)
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6 glGetLight - return light source parameter values
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9 void glGetLightfv(GLenum light, GLenum pname, GLfloat * params);
10 void glGetLightiv(GLenum light, GLenum pname, GLint * params);
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14 light
15 Specifies a light source. The number of possible lights depends on
16 the implementation, but at least eight lights are supported. They
17 are identified by symbolic names of the form GL_LIGHT i where i
18 ranges from 0 to the value of GL_MAX_LIGHTS - 1.
19 pname
21 Specifies a light source parameter for light. Accepted symbolic
22 names are GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR, GL_POSITION,
23 GL_SPOT_DIRECTION, GL_SPOT_EXPONENT, GL_SPOT_CUTOFF,
24 GL_CONSTANT_ATTENUATION, GL_LINEAR_ATTENUATION, and
25 GL_QUADRATIC_ATTENUATION.
26 params
28 Returns the requested data.
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31 glGetLight returns in params the value or values of a light source
32 parameter. light names the light and is a symbolic name of the form
33 GL_LIGHT i where i ranges from 0 to the value of GL_MAX_LIGHTS - 1.
34 GL_MAX_LIGHTS is an implementation dependent constant that is greater
35 than or equal to eight. pname specifies one of ten light source
36 parameters, again by symbolic name.
37 The following parameters are defined:
39 GL_AMBIENT
41 params returns four integer or floating-point values representing
42 the ambient intensity of the light source. Integer values, when
43 requested, are linearly mapped from the internal floating-point
44 representation such that 1.0 maps to the most positive
45 representable integer value, and -1.0 maps to the most negative
46 representable integer value. If the internal value is outside the
47 range -1 1, the corresponding integer return value is undefined.
48 The initial value is (0, 0, 0, 1).
49 GL_DIFFUSE
51 params returns four integer or floating-point values representing
52 the diffuse intensity of the light source. Integer values, when
53 requested, are linearly mapped from the internal floating-point
54 representation such that 1.0 maps to the most positive
55 representable integer value, and -1.0 maps to the most negative
56 representable integer value. If the internal value is outside the
57 range -1 1, the corresponding integer return value is undefined.
58 The initial value for GL_LIGHT0 is (1, 1, 1, 1); for other lights,
59 the initial value is (0, 0, 0, 0).
60 GL_SPECULAR
62 params returns four integer or floating-point values representing
63 the specular intensity of the light source. Integer values, when
64 requested, are linearly mapped from the internal floating-point
65 representation such that 1.0 maps to the most positive
66 representable integer value, and -1.0 maps to the most negative
67 representable integer value. If the internal value is outside the
68 range -1 1, the corresponding integer return value is undefined.
69 The initial value for GL_LIGHT0 is (1, 1, 1, 1); for other lights,
70 the initial value is (0, 0, 0, 0).
71 GL_POSITION
73 params returns four integer or floating-point values representing
74 the position of the light source. Integer values, when requested,
75 are computed by rounding the internal floating-point values to the
76 nearest integer value. The returned values are those maintained in
77 eye coordinates. They will not be equal to the values specified
78 using glLight(), unless the modelview matrix was identity at the
79 time glLight() was called. The initial value is (0, 0, 1, 0).
80 GL_SPOT_DIRECTION
82 params returns three integer or floating-point values representing
83 the direction of the light source. Integer values, when requested,
84 are computed by rounding the internal floating-point values to the
85 nearest integer value. The returned values are those maintained in
86 eye coordinates. They will not be equal to the values specified
87 using glLight(), unless the modelview matrix was identity at the
88 time glLight() was called. Although spot direction is normalized
89 before being used in the lighting equation, the returned values are
90 the transformed versions of the specified values prior to
91 normalization. The initial value is 0 0 -1.
92 GL_SPOT_EXPONENT
94 params returns a single integer or floating-point value
95 representing the spot exponent of the light. An integer value, when
96 requested, is computed by rounding the internal floating-point
97 representation to the nearest integer. The initial value is 0.
98 GL_SPOT_CUTOFF
100 params returns a single integer or floating-point value
101 representing the spot cutoff angle of the light. An integer value,
102 when requested, is computed by rounding the internal floating-point
103 representation to the nearest integer. The initial value is 180.
104 GL_CONSTANT_ATTENUATION
106 params returns a single integer or floating-point value
107 representing the constant (not distance-related) attenuation of the
108 light. An integer value, when requested, is computed by rounding
109 the internal floating-point representation to the nearest integer.
110 The initial value is 1.
111 GL_LINEAR_ATTENUATION
113 params returns a single integer or floating-point value
114 representing the linear attenuation of the light. An integer value,
115 when requested, is computed by rounding the internal floating-point
116 representation to the nearest integer. The initial value is 0.
117 GL_QUADRATIC_ATTENUATION
119 params returns a single integer or floating-point value
120 representing the quadratic attenuation of the light. An integer
121 value, when requested, is computed by rounding the internal
122 floating-point representation to the nearest integer. The initial
123 value is 0.
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126 It is always the case that GL_LIGHT i = GL_LIGHT0 + i.
127 If an error is generated, no change is made to the contents of params.
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131 GL_INVALID_ENUM is generated if light or pname is not an accepted
132 value.
133 GL_INVALID_OPERATION is generated if glGetLight is executed between the
135 execution of glBegin() and the corresponding execution of glEnd().
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138 glLight()
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141 Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
142 under the SGI Free Software B License. For details, see
143 http://oss.sgi.com/projects/FreeB/.
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146 opengl.org
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