glEvalPoint, glEvalPoint1, glEvalPoint2 - generate and
evaluate a single point in a mesh
void glEvalPoint1(
GLint i ); void glEvalPoint2(
GLint i,
GLint j );
Specifies the integer value for grid domain variable i.
Specifies the integer value for grid domain variable j
(glEvalPoint2() only).
glMapGrid() and glEvalMesh() are used in tandem to efficiently
generate and evaluate a series of evenly spaced
map domain values. glEvalPoint() can be used to evaluate
a single grid point in the same gridspace that is traversed
by glEvalMesh(). Calling glEvalPoint1() is equivalent
to calling
glEvalCoord1( i . DELTA u + u[1] );
where
DELTA u = ( u[2] - u[1] ) / n
and n, u[1], and u[2] are the arguments to the most recent
glMapGrid1() command. The one absolute numeric requirement
is that if i=n, then the value computed from i . DELTA u +
u[1] is exactly u[2].
In the two-dimensional case, glEvalPoint2, let
DELTA u = u[2] - u[1] ) / n
DELTA v = ( v[2] - v[1] ) / m,
where n, u[1], u[2], m, v[1], and v[2] are the arguments
to the most recent glMapGrid2() command. Then the glEvalPoint2()
command is equivalent to calling
glEvalCoord2( i . DELTA u + u[1], j. DELTA v + v[1] );
The only absolute numeric requirements are that if i=n,
then the value computed from i . DELTA u + u[1] is exactly
u[2], and if j=m, then the value computed from i . DELTA v
+ v[1] is exactly v[2].
glGet() with argument GL_MAP1_GRID_DOMAIN
glGet() with argument GL_MAP2_GRID_DOMAIN
glGet() with argument GL_MAP1_GRID_SEGMENTS
glGet() with argument GL_MAP2_GRID_SEGMENTS
glEvalCoord(3), glEvalMesh(3), glMap1(3), glMap2(3),
glMapGrid(3)
glEvalPoint(3G)
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