glGetLight(3G) OpenGL Reference glGetLight(3G)
NAME
glGetLightfv, glGetLightiv - 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 GLLIGHTi where
0 < i < GLMAXLIGHTS.
pname Specifies a light source parameter for light. Accepted symbolic
names are GLAMBIENT, GLDIFFUSE, GLSPECULAR, GLPOSITION,
GLSPOTDIRECTION, GLSPOTEXPONENT, GLSPOTCUTOFF,
GLCONSTANTATTENUATION, GLLINEARATTENUATION , and
GLQUADRATICATTENUATION.
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
GLLIGHTi for 0<i<GLMAXLIGHTS, where GLMAXLIGHTS 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:
GLAMBIENT 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).
GLDIFFUSE 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
Page 1
glGetLight(3G) OpenGL Reference glGetLight(3G)
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 GLLIGHT0 is (1, 1, 1, 1); for
other lights, the initial value is (0, 0, 0, 0).
GLSPECULAR 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 GLLIGHT0 is (1, 1, 1, 1); for
other lights, the initial value is (0, 0, 0, 0).
GLPOSITION 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).
GLSPOTDIRECTION 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).
GLSPOTEXPONENT 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.
GLSPOTCUTOFF params returns a single integer or floating-point
value representing the spot cutoff angle of the
light. An integer value, when requested, is computed
Page 2
glGetLight(3G) OpenGL Reference glGetLight(3G)
by rounding the internal floating-point
representation to the nearest integer. The initial
value is 180.
GLCONSTANTATTENUATION
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.
GLLINEARATTENUATION
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.
GLQUADRATICATTENUATION
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 GLLIGHTi = GLLIGHT0 + i.
If an error is generated, no change is made to the contents of params.
ERRORS
GLINVALIDENUM is generated if light or pname is not an accepted value.
GLINVALIDOPERATION is generated if glGetLight is executed between the
execution of glBegin and the corresponding execution of glEnd.
SEE ALSO
glLight
Page 3