glEvalPoint.3gl

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·du + u );
                                                1
				    where

				du = (u	-u )/n
				       2  1

  and n, u , and u  are	the arguments to the most recent glMapGrid1 command.
          1       2
  The one absolute numeric requirement is that if i = n, then the value
  computed from	i·du + u  is exactly u .
			1	      2

  In the two-dimensional case, glEvalPoint2, let

				 du=(u -u )/n
				      2	 1
				 dv=(v -v )/m
				      2	 1
  where	n, u , u , m, v	, and v	 are the arguments to the most recent
            1   2      1       2
  glMapGrid2 command.  Then the glEvalPoint2 command is	equivalent to calling

		      glEvalCoord2(i·du	+ u , j·dv + v );
				           1          1

  The only absolute numeric requirements are that if i = n, then the value
  computed from	i·du + u  is exactly u , and if	j = m, then the	value
                        1             2
  computed from	j·dv + v  is exactly v .
			1	      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

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Last Edited: Fri Dec 6 11:18:03 EST 1996 by AFV
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