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2.13.2 Lighting Parameter SpecificationLighting parameters are divided into three categories: material parameters, light source parameters, and lighting model parameters (see Table 2.7). Sets of lighting parameters are specified with
void Material[if] ( enum face, enum pname, T param ) ;
pname is a symbolic constant indicating
which parameter is to be set (see Table 2.8).
In the vector versions of the commands,
params is a pointer to a group of values to which to set the indicated
parameter.
The number of values pointed to depends on the parameter being set.
In the non-vector versions, param is a value to which to set
a single-valued parameter.
(If param corresponds to a multi-valued parameter,
the error INVALID_ENUM results.)
For the Material command,
face must be one of FRONT,
BACK, or FRONT_AND_BACK,
indicating that the property name of the front or back material,
or both,
respectively,
should be set.
In the case of Light ,
light is a symbolic constant of the form LIGHTi,
indicating that light i is to have the specified parameter set.
The constants obey
Table 2.8
gives,
for each of the three parameter groups,
the correspondence between the pre-defined constant names and
their names in the lighting equations,
along with
the number of values that must be specified with each.
Color parameters specified with Material and Light
are converted to floating-point values (if specified as integers)
as indicated in Table 2.6 for signed integers.
The error INVALID_VALUE occurs if a specified lighting
parameter lies outside the allowable range given in Table 2.7.
(The symbol ``
The current model-view matrix is applied to the position parameter indicated with Light for a particular light source when that position is specified. These transformed values are the values used in the lighting equation.
The spotlight direction is transformed when it is specified
using only the upper leftmost 3x3 portion of the model-view
matrix. That is, if is transformed to
An individual light is enabled or disabled by calling Enable or Disable with the symbolic value LIGHTi (i is in the range 0 to n-1, where n is the implementation-dependent number of lights). If light i is disabled, the ith term in the lighting equation is effectively removed from the summation.
![]() ![]() ![]() ![]() ![]() Next: 2.13.3 ColorMaterial Up: 2.13 Colors and Coloring Previous: Lighting Operation David Blythe Sat Mar 29 02:23:21 PST 1997
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