NAME
glGetLightfv, glGetLightiv
- return light source parameter values
C SPECIFICATION
void ggllGGeettLLiigghhttffvv(
GLenum _l_i_g_h_t,
GLenum _p_n_a_m_e,
GLfloat _*_p_a_r_a_m_s )
void ggllGGeettLLiigghhttiivv(
GLenum _l_i_g_h_t,
GLenum _p_n_a_m_e,
GLint _*_p_a_r_a_m_s )
delim $$
PARAMETERS
-
_l_i_g_h_t
-
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 GGLL__LLIIGGHHTT$i$
where 0 <= $ i $ < GGLL__MMAAXX__LLIIGGHHTTSS.
-
_p_n_a_m_e
-
Specifies a light source parameter for _l_i_g_h_t.
Accepted symbolic names are
GGLL__AAMMBBIIEENNTT,
GGLL__DDIIFFFFUUSSEE,
GGLL__SSPPEECCUULLAARR,
GGLL__PPOOSSIITTIIOONN,
GGLL__SSPPOOTT__DDIIRREECCTTIIOONN,
GGLL__SSPPOOTT__EEXXPPOONNEENNTT,
GGLL__SSPPOOTT__CCUUTTOOFFFF,
GGLL__CCOONNSSTTAANNTT__AATTTTEENNUUAATTIIOONN,
GGLL__LLIINNEEAARR__AATTTTEENNUUAATTIIOONN, and
GGLL__QQUUAADDRRAATTIICC__AATTTTEENNUUAATTIIOONN.
-
_p_a_r_a_m_s
-
Returns the requested data.
DESCRIPTION
ggllGGeettLLiigghhtt returns in _p_a_r_a_m_s the value or values of a light source parameter.
_l_i_g_h_t names the light and is a symbolic name of the form GGLL__LLIIGGHHTT$i$
for 0 <= $i$ < GGLL__MMAAXX__LLIIGGHHTTSS,
where GGLL__MMAAXX__LLIIGGHHTTSS is an implementation dependent constant that is
greater than or equal to eight.
_p_n_a_m_e specifies one of ten light source parameters,
again by symbolic name.
The following parameters are defined:
-
GGLL__AAMMBBIIEENNTT
-
_p_a_r_a_m_s 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).
-
GGLL__DDIIFFFFUUSSEE
-
_p_a_r_a_m_s 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 GGLL__LLIIGGHHTT00 is (1, 1, 1, 1); for other lights, the
initial value is (0, 0, 0, 0).
-
GGLL__SSPPEECCUULLAARR
-
_p_a_r_a_m_s 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 GGLL__LLIIGGHHTT00 is (1, 1, 1, 1); for other lights, the
initial value is (0, 0, 0, 0).
-
GGLL__PPOOSSIITTIIOONN
-
_p_a_r_a_m_s 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 ggllLLiigghhtt,
unless the modelview matrix was identity at the time ggllLLiigghhtt was
called. The initial value is (0, 0, 1, 0).
-
GGLL__SSPPOOTT__DDIIRREECCTTIIOONN
-
_p_a_r_a_m_s 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 ggllLLiigghhtt,
unless the modelview matrix was identity at the time ggllLLiigghhtt 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).
-
GGLL__SSPPOOTT__EEXXPPOONNEENNTT
-
_p_a_r_a_m_s 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.
-
GGLL__SSPPOOTT__CCUUTTOOFFFF
-
_p_a_r_a_m_s 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.
-
GGLL__CCOONNSSTTAANNTT__AATTTTEENNUUAATTIIOONN
-
_p_a_r_a_m_s 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.
-
GGLL__LLIINNEEAARR__AATTTTEENNUUAATTIIOONN
-
_p_a_r_a_m_s 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.
-
GGLL__QQUUAADDRRAATTIICC__AATTTTEENNUUAATTIIOONN
-
_p_a_r_a_m_s 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 GGLL__LLIIGGHHTT$i$ = GGLL__LLIIGGHHTT00 + $i$.
If an error is generated,
no change is made to the contents of _p_a_r_a_m_s.
ERRORS
GGLL__IINNVVAALLIIDD__EENNUUMM is generated if _l_i_g_h_t or _p_n_a_m_e is not an
accepted value.
GGLL__IINNVVAALLIIDD__OOPPEERRAATTIIOONN is generated if ggllGGeettLLiigghhtt
is executed between the execution of ggllBBeeggiinn
and the corresponding execution of ggllEEnndd.
SEE ALSO
ggllLLiigghhtt((33GG))