GLEVALPOINT() MachTen Programmer’s Manual GLEVALPOINT()

NAME
glEvalPoint1, glEvalPoint2 - generate and evaluate a sin-
gle point in a mesh

C SPECIFICATION
void glEvalPoint1( GLint i )
void glEvalPoint2( GLint i,
GLint j )

delim $$

PARAMETERS
i Specifies the integer value for grid domain variable
$i$.

j Specifies the integer value for grid domain variable
$j$ (glEvalPoint2 only).

DESCRIPTION
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 glE-
valMesh. Calling glEvalPoint1 is equivalent to calling

glEvalCoord1(i . DELTA u + u );
1
where

DELTA u = (u - u ) / n
2 1

and n, u , and u
1 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 is exactly u .
1 2

In the two-dimensional case, glEvalPoint2, let
DELTA u = (u - u )/n
2 1

DELTA v = (v - v )/m
2 1

where n, u , u , m, v , and v
1 2 1 2

are the arguments to the most recent glMapGrid2 command.
Then the glEvalPoint2 command is equivalent to calling

glEvalCoord2(i . DELTA u + u , j . DELTA v + v );
1 1

The only absolute numeric requirements are that if
$i~=~n$, then the value computed from

i . DELTA u + u is exactly u ,
1 2
and if $j~=~m$, then the value computed from

j cdot DELTA v + v is exactly v .
1 2

ASSOCIATED GETS
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

SEE ALSO
glEvalCoord, glEvalMesh, glMap1, glMap2, glMapGrid

MachTen 2