
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_LIGHTi 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_LIGHTi 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 floatingpoint values representing the ambient
intensity of the light source. Integer values, when requested, are linearly mapped
from the internal floatingpoint 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 floatingpoint values representing the diffuse
intensity of the light source. Integer values, when requested, are linearly mapped
from the internal floatingpoint 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 floatingpoint values representing the specular
intensity of the light source. Integer values, when requested, are linearly mapped
from the internal floatingpoint 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 floatingpoint values representing the position of the
light source. Integer values, when requested, are computed by rounding the internal
floatingpoint 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 floatingpoint values representing the direction of
the light source. Integer values, when requested, are computed by rounding the
internal floatingpoint 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 floatingpoint value representing the spot exponent
of the light. An integer value, when requested, is computed by rounding the internal
floatingpoint representation to the nearest integer. The initial value is 0.
GL_SPOT_CUTOFF
params returns a single integer or floatingpoint value representing the spot cutoff
angle of the light. An integer value, when requested, is computed by rounding the
internal floatingpoint representation to the nearest integer. The initial value is
180.
GL_CONSTANT_ATTENUATION
params returns a single integer or floatingpoint value representing the constant (not
distancerelated) attenuation of the light. An integer value, when requested, is
computed by rounding the internal floatingpoint representation to the nearest
integer. The initial value is 1.
GL_LINEAR_ATTENUATION
params returns a single integer or floatingpoint value representing the linear
attenuation of the light. An integer value, when requested, is computed by rounding
the internal floatingpoint representation to the nearest integer. The initial value
is 0.
GL_QUADRATIC_ATTENUATION
params returns a single integer or floatingpoint value representing the quadratic
attenuation of the light. An integer value, when requested, is computed by rounding
the internal floatingpoint representation to the nearest integer. The initial value
is 0.
NOTES
It is always the case that GL_LIGHTi = 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 (C) 19912006 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 06/10/2014 GLGETLIGHT(3G) 
