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
); |
Python Specification
glGetLightfv
|
( |
light
,
pname
) →
params
|
glGetLightiv
|
( |
light
,
pname
) →
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_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.