# Method GL.glEvalPoint()

Method glEvalPoint

  `void glEvalPoint(int|array(int) i, int|void j)`

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 glEvalPoint is equivalent to calling .nf

  glEvalCoord1(i . DELTA u + u ); 1 where

  DELTA u = (u - u ) / n 2 1

  and n, u , and u 1 2

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

  .fi

  In the two-dimensional case, glEvalPoint, let .nf DELTA u = (u - u )/n 2 1

  DELTA v = (v - v )/m 2 1

  where n, u , u , m, v , and v 1 2 1 2

  .fi are the arguments to the most recent glMapGrid2 command. Then the glEvalPoint command is equivalent to calling .nf

  glEvalCoord2(i . DELTA u + u , j . DELTA v + v ); 1 1

  .fi The only absolute numeric requirements are that if i~=~n, then the value computed from .nf

  i . DELTA u + u is exactly u , 1 2 .fi and if j~=~m, then the value computed from .nf

  j cdot DELTA v + v is exactly v . 1 2

Parameter `i`

  Specifies the integer value for grid domain variable i.

Parameter `j`

  Specifies the integer value for grid domain variable j (glEvalPoint only).