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 0 < $ i $ < GL_MAX_LIGHTS.
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$i$
for 0 < $i$ < GL_MAX_LIGHTS,
where 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.
