glGetLight(3G)glGetLight(3G)NAME
glGetLight, glGetLightfv, glGetLightiv - return light source parameter
values
SYNOPSIS
void glGetLightfv(
GLenum light,
GLenum pname,
GLfloat *params ); void glGetLightiv(
GLenum light,
GLenum pname,
GLint *params );
PARAMETERS
Specifies a light source. The number of possible lights depends on the
implementation, but at least eight lights are supported. They are iden‐
tified by symbolic names of the form GL_LIGHTi where 0 <= i <
GL_MAX_LIGHTS. 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_ATTEN‐
UATION, GL_LINEAR_ATTENUATION, and GL_QUADRATIC_ATTENUATION. Returns
the requested data.
DESCRIPTIONglGetLight() 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 imple‐
mentation 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: 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 nega‐
tive 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). params returns four integer or float‐
ing-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 nega‐
tive 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 ini‐
tial value is (0, 0, 0, 0). 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 repre‐
sentable 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). 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).
params returns three integer or floating-point values representing the
direction of the light source. Integer values, when requested, are com‐
puted by rounding the internal floating-point values to the nearest
integer value. The returned values are those maintained in eye coordi‐
nates. 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). params returns a single integer or floating-point value repre‐
senting the spot exponent of the light. An integer value, when
requested, is computed by rounding the internal floating-point repre‐
sentation to the nearest integer. The initial value is 0. params
returns a single integer or floating-point value representing the spot
cutoff angle of the light. An integer value, when requested, is com‐
puted by rounding the internal floating-point representation to the
nearest integer. The initial value is 180. params returns a single
integer or floating-point value representing the constant (not dis‐
tance-related) attenuation of the light. An integer value, when
requested, is computed by rounding the internal floating-point repre‐
sentation to the nearest integer. The initial value is 1. params
returns a single integer or floating-point value representing the lin‐
ear attenuation of the light. An integer value, when requested, is com‐
puted by rounding the internal floating-point representation to the
nearest integer. The initial value is 0. params returns a single inte‐
ger 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_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 ALSOglLight(3)glGetLight(3G)