glGetLight, glGetLightfv, glGetLightiv - return light
source parameter values
void glGetLightfv(
GLenum light,
GLenum pname,
GLfloat *params ); void glGetLightiv(
GLenum light,
GLenum pname,
GLint *params );
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. 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. Returns the requested data.
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: 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 floatingpoint
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). params returns four integer or floatingpoint
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).
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). 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 floatingpoint
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 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). params returns a single integer or floatingpoint
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. 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. 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 floatingpoint
representation to the nearest integer. The initial
value is 1. params returns a single integer or floatingpoint
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. 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 floatingpoint
representation to the nearest integer. The initial
value is 0.
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.
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().
glLight(3)
glGetLight(3G)
[ Back ] |
