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*du+u1);

where

du = (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*du+u1 is exactly u2.

In the two-dimensional case, glEvalPoint2, let

du = (u2-u1)/n

dv = (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*du+u1, j*dv+v1);

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

ASSOCIATED GETS