GLGETLIGHT(3G) 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 GL_LIGHTi 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_LIGHTi 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 nor-
malization. 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 inte-
ger 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_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(3G)
GLGETLIGHT(3G)