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 + u1);
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 Δ v = v 2 - v 1 m 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 + u1, j · Δ v + v1);
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.
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/.
glEvalPoint: man2/glEvalPoint.xml
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
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 Δ v = v 2 - v 1 m 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
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.