glEvalPoint

glEvalPoint

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 ?Δu + u1);

where

Δu = (u2 - u1 ) / n

and n, u1, and u2 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 ?Δu + u1 is exactly u2.

In the two-dimensional case, glEvalPoint2, let

Δu = (u2 - u1 )/n

Δv = (v2 - v1 )/m

where n, u1, u2, m, v1, and v2 are the arguments to the most recent glMapGrid2 command. Then the glEvalPoint2 command is equivalent to calling

glEvalCoord2(i ?Δu + u1, j ?Δv + v1);

The only absolute numeric requirements are that if i = n, then the value computed from i ?Δu + u1 is exactly u2, and if j = m, then the value computed from j ?Δv + v1 is exactly v2.

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"