glEvalPoint1, glEvalPoint2 - generate and evaluate a single point in a mesh
void glEvalPoint1( GLint i ) void glEvalPoint2( GLint i, GLint j )
i Specifies the integer value for grid domain variable i.
j 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·du + u );
1
where
du = (u -u )/n
2 1
and n, u , and u are the arguments to the most recent glMapGrid1 command.
1 2
The one absolute numeric requirement is that if i = n, then the value
computed from i·du + u is exactly u .
1 2
In the two-dimensional case, glEvalPoint2, let
du=(u -u )/n
2 1
dv=(v -v )/m
2 1
where n, u , u , m, v , and v are the arguments to the most recent
1 2 1 2
glMapGrid2 command. Then the glEvalPoint2 command is equivalent to calling
glEvalCoord2(i·du + u , j·dv + v );
1 1
The only absolute numeric requirements are that if i = n, then the value
computed from i·du + u is exactly u , and if j = m, then the value
1 2
computed from j·dv + v is exactly v .
1 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, glEvalMesh, glMap1, glMap2, glMapGrid
Introduction | Alphabetic | Specification
Last Edited: Mon, May 22, 1995