NAME

glEvalPoint1, glEvalPoint2 - generate and evaluate a single point in a mesh

C SPECIFICATION

void glEvalPoint1( GLint i )

void glEvalPoint2( GLint i,

	GLint j )

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 glEvalMesh. 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