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GLEVALPOINT(3G)			 OpenGL Manual		       GLEVALPOINT(3G)

NAME
       glEvalPoint - 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
				       ⋅
				       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.PP 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

				 +

				     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.

ASSOCIATED GETS
       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

SEE ALSO
       glEvalCoord(), glEvalMesh(), glMap1(), glMap2(), glMapGrid()

COPYRIGHT
       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/.

AUTHORS
       opengl.org

opengl.org			  04/29/2014		       GLEVALPOINT(3G)

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