NAME¶
glGetMap - return evaluator parameters
C SPECIFICATION¶
void glGetMapdv(GLenum target,
GLenum query,
GLdouble * v);
void glGetMapfv(GLenum target,
GLenum query,
GLfloat * v);
void glGetMapiv(GLenum target,
GLenum query,
GLint * v);
PARAMETERS¶
target
Specifies the symbolic name of a map. Accepted values are
GL_MAP1_COLOR_4, GL_MAP1_INDEX, GL_MAP1_NORMAL,
GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2,
GL_MAP1_TEXTURE_COORD_3, GL_MAP1_TEXTURE_COORD_4,
GL_MAP1_VERTEX_3, GL_MAP1_VERTEX_4, GL_MAP2_COLOR_4,
GL_MAP2_INDEX, GL_MAP2_NORMAL, GL_MAP2_TEXTURE_COORD_1,
GL_MAP2_TEXTURE_COORD_2, GL_MAP2_TEXTURE_COORD_3,
GL_MAP2_TEXTURE_COORD_4, GL_MAP2_VERTEX_3, and
GL_MAP2_VERTEX_4.
query
Specifies which parameter to return. Symbolic names
GL_COEFF, GL_ORDER, and GL_DOMAIN are accepted.
v
Returns the requested data.
DESCRIPTION¶
glMap1() and glMap2() define evaluators.
glGetMap returns evaluator parameters. target chooses a map,
query selects a specific parameter, and v points to storage
where the values will be returned.
The acceptable values for the target parameter are
described in the glMap1() and glMap2() reference pages.
query can assume the following values:
GL_COEFF
v returns the control points for the evaluator
function. One-dimensional evaluators return order control points, and
two-dimensional evaluators return uorder × vorder control points. Each
control point consists of one, two, three, or four integer, single-precision
floating-point, or double-precision floating-point values, depending on the
type of the evaluator. The GL returns two-dimensional control points in
row-major order, incrementing the uorder index quickly and the vorder index
after each row. Integer values, when requested, are computed by rounding the
internal floating-point values to the nearest integer values.
GL_ORDER
v returns the order of the evaluator function.
One-dimensional evaluators return a single value, order. The initial value is
1. Two-dimensional evaluators return two values, uorder and vorder. The
initial value is 1,1.
GL_DOMAIN
v returns the linear u and v mapping parameters.
One-dimensional evaluators return two values, u1 and u2, as specified by
glMap1(). Two-dimensional evaluators return four values (u1, u2, v1,
and v2) as specified by glMap2(). 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 contents of
v.
ERRORS¶
GL_INVALID_ENUM is generated if either target or
query is not an accepted value.
GL_INVALID_OPERATION is generated if glGetMap is
executed between the execution of glBegin() and the corresponding
execution of glEnd().
SEE ALSO¶
glEvalCoord(), glMap1(), glMap2()