glEvalPoint — generate and evaluate a single point in a mesh
void glEvalPoint1 (GLint i);
void glEvalPoint2 (GLint i,
GLint j);
Specifies the integer value for grid domain variable i.
Specifies the integer value for grid domain variable j (glEvalPoint2 only).
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, v2 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.
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