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, the value computed from i * Δu + u₁ is exactly u.

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, the value computed from i * Δu + u₁ is exactly u₂, and if j = m, the value computed from j * Δv + v₁ is exactly v₂.

ASSOCIATED GETS