glGetLight man page on RedHat
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GLGETLIGHT(3G) OpenGL Manual GLGETLIGHT(3G)
NAME
glGetLight - return light source parameter values
C SPECIFICATION
void glGetLightfv(GLenum light, GLenum pname, GLfloat * params);
void glGetLightiv(GLenum light, GLenum pname, GLint * params);
PARAMETERS
light
Specifies a light source. The number of possible lights depends on
the implementation, but at least eight lights are supported. They
are identified by symbolic names of the form GL_LIGHT i where i
ranges from 0 to the value of GL_MAX_LIGHTS - 1.
pname
Specifies a light source parameter for light. Accepted symbolic
names are GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR, GL_POSITION,
GL_SPOT_DIRECTION, GL_SPOT_EXPONENT, GL_SPOT_CUTOFF,
GL_CONSTANT_ATTENUATION, GL_LINEAR_ATTENUATION, and
GL_QUADRATIC_ATTENUATION.
params
Returns the requested data.
DESCRIPTION
glGetLight returns in params the value or values of a light source
parameter. light names the light and is a symbolic name of the form
GL_LIGHT i where i ranges from 0 to the value of GL_MAX_LIGHTS - 1.
GL_MAX_LIGHTS is an implementation dependent constant that is greater
than or equal to eight. pname specifies one of ten light source
parameters, again by symbolic name.
The following parameters are defined:
GL_AMBIENT
params returns four integer or floating-point values representing
the ambient intensity of the light source. Integer values, when
requested, are linearly mapped from the internal floating-point
representation such that 1.0 maps to the most positive
representable integer value, and -1.0 maps to the most negative
representable integer value. If the internal value is outside the
range -1 1, the corresponding integer return value is undefined.
The initial value is (0, 0, 0, 1).
GL_DIFFUSE
params returns four integer or floating-point values representing
the diffuse intensity of the light source. Integer values, when
requested, are linearly mapped from the internal floating-point
representation such that 1.0 maps to the most positive
representable integer value, and -1.0 maps to the most negative
representable integer value. If the internal value is outside the
range -1 1, the corresponding integer return value is undefined.
The initial value for GL_LIGHT0 is (1, 1, 1, 1); for other lights,
the initial value is (0, 0, 0, 0).
GL_SPECULAR
params returns four integer or floating-point values representing
the specular intensity of the light source. Integer values, when
requested, are linearly mapped from the internal floating-point
representation such that 1.0 maps to the most positive
representable integer value, and -1.0 maps to the most negative
representable integer value. If the internal value is outside the
range -1 1, the corresponding integer return value is undefined.
The initial value for GL_LIGHT0 is (1, 1, 1, 1); for other lights,
the initial value is (0, 0, 0, 0).
GL_POSITION
params returns four integer or floating-point values representing
the position of the light source. Integer values, when requested,
are computed by rounding the internal floating-point values to the
nearest integer value. The returned values are those maintained in
eye coordinates. They will not be equal to the values specified
using glLight(), unless the modelview matrix was identity at the
time glLight() was called. The initial value is (0, 0, 1, 0).
GL_SPOT_DIRECTION
params returns three integer or floating-point values representing
the direction of the light source. Integer values, when requested,
are computed by rounding the internal floating-point values to the
nearest integer value. The returned values are those maintained in
eye coordinates. They will not be equal to the values specified
using glLight(), unless the modelview matrix was identity at the
time glLight() was called. Although spot direction is normalized
before being used in the lighting equation, the returned values are
the transformed versions of the specified values prior to
normalization. The initial value is 0 0 -1.
GL_SPOT_EXPONENT
params returns a single integer or floating-point value
representing the spot exponent of the light. An integer value, when
requested, is computed by rounding the internal floating-point
representation to the nearest integer. The initial value is 0.
GL_SPOT_CUTOFF
params returns a single integer or floating-point value
representing the spot cutoff angle of the light. An integer value,
when requested, is computed by rounding the internal floating-point
representation to the nearest integer. The initial value is 180.
GL_CONSTANT_ATTENUATION
params returns a single integer or floating-point value
representing the constant (not distance-related) attenuation of the
light. An integer value, when requested, is computed by rounding
the internal floating-point representation to the nearest integer.
The initial value is 1.
GL_LINEAR_ATTENUATION
params returns a single integer or floating-point value
representing the linear attenuation of the light. An integer value,
when requested, is computed by rounding the internal floating-point
representation to the nearest integer. The initial value is 0.
GL_QUADRATIC_ATTENUATION
params returns a single integer or floating-point value
representing the quadratic attenuation of the light. An integer
value, when requested, is computed by rounding the internal
floating-point representation to the nearest integer. The initial
value is 0.
NOTES
It is always the case that GL_LIGHT i = GL_LIGHT0 + i.
If an error is generated, no change is made to the contents of params.
ERRORS
GL_INVALID_ENUM is generated if light or pname is not an accepted
value.
GL_INVALID_OPERATION is generated if glGetLight is executed between the
execution of glBegin() and the corresponding execution of glEnd().
SEE ALSO
glLight()
COPYRIGHT
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
under the SGI Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLGETLIGHT(3G)
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