glGetLight(3) glGetLight(3)
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 sym-
bolic 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 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:
GL_AMBIENT params returns four integer or floating-point val-
ues representing the ambient intensity of the light
source. Integer values, when requested, are lin-
early mapped from the internal floating-point rep-
resentation 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 val-
ues representing the diffuse intensity of the light
source. Integer values, when requested, are lin-
early mapped from the internal floating-point rep-
resentation 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 val-
ues 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 posi-
tive 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 unde-
fined. 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 val-
ues 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 val-
ues 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 normal-
ization. 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 com-
puted by rounding the internal floating-point rep-
resentation 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 near-
est 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 com-
puted by rounding the internal floating-point rep-
resentation 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 com-
puted by rounding the internal floating-point rep-
resentation 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(3)
glGetLight(3)
Mac OS X 10.6 - Generated Thu Sep 17 20:20:21 CDT 2009