glEvalPoint.3G man page
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 ⋅ Δ u + u 1 );
where Δ u = u 2 - u 1 n
and n, u 1, and u 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 ⋅ Δ u + u 1 is exactly u 2.
In the two-dimensional case, glEvalPoint2, let
Δ u = u 2 - u 1 n
where n, u 1, u 2, m, v 1, and v 2 are the arguments to the most recent glMapGrid2() command. Then the glEvalPoint2 command is equivalent to calling
glEvalCoord2( i ⋅ Δ u + u 1 , j ⋅ Δ v + v 1 );
The only absolute numeric requirements are that if i = n, then the value computed from i ⋅ Δ u + u 1 is exactly u 2, and if j = m, then the value computed from j ⋅ Δ v + v 1 is exactly v 2.
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
glEvalCoord(), glEvalMesh(), glMap1(), glMap2(), glMapGrid()
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.
glEvalPoint1.3G(3) and glEvalPoint2.3G(3) are aliases of glEvalPoint.3G(3).