- return material parameters
C SPECIFICATION
PARAMETERS
_param1 Specifies which of the two materials is being
queried. GL_FRONT or GL_BACK are accepted, rep-
resenting the front and back materials, respec-
tively.
_param2 Specifies the material parameter to return.
GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR, GL_EMISSION,
GL_SHININESS, and GL_COLOR_INDEXES are accepted.
_param3 Returns the requested data.
DESCRIPTION
glGetMaterial returns in _param3 the value or values of
parameter _param2 of material _param1. Six parameters are
defined:
GL_AMBIENT _param3 returns four integer or
floating-point values representing
the ambient reflectance of the mate-
rial. Integer values, when
requested, are linearly mapped from
the internal floating-point repre-
sentation 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 cor-
responding integer return value is
undefined. The initial value is
(0.2, 0.2, 0.2, 1.0)
GL_DIFFUSE _param3 returns four integer or
floating-point values representing
the diffuse reflectance of the mate-
rial. Integer values, when
requested, are linearly mapped from
the internal floating-point repre-
sentation 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 cor-
responding integer return value is
undefined. The initial value is
(0.8, 0.8, 0.8, 1.0).
undefined. The initial value is (0,
0, 0, 1).
GL_EMISSION _param3 returns four integer or
floating-point values representing
the emitted light intensity of the
material. Integer values, when
requested, are linearly mapped from
the internal floating-point repre-
sentation 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, 1.0], the
corresponding integer return value
is undefined. The initial value is
(0, 0, 0, 1).
GL_SHININESS _param3 returns one integer or
floating-point value representing
the specular exponent of the mate-
rial. Integer values, when
requested, are computed by rounding
the internal floating-point value to
the nearest integer value. The ini-
tial value is 0.
GL_COLOR_INDEXES _param3 returns three integer or
floating-point values representing
the ambient, diffuse, and specular
indices of the material. These
indices are used only for color
index lighting. (All the other
parameters are used only for RGBA
lighting.) Integer values, when
requested, are computed by rounding
the internal floating-point values
to the nearest integer values.
NOTES
If an error is generated, no change is made to the con-
tents of _param3.
ERRORS
GL_INVALID_ENUM is generated if _param1 or _param2 is not
an accepted value.
GL_INVALID_OPERATION is generated if glGetMaterial is exe-
cuted between the execution of glBegin and the correspond-
ing execution of glEnd.