Table of Contents

## Name

glEvalPoint1, glEvalPoint2 - generate and evaluate a single point

in a mesh

## C Specification

void glEvalPoint1( GLint i )

void glEvalPoint2( GLint i,

        GLint j )

eqn not supported

## 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$^cdot^DELTA u ~+~ u sub 1$ );where

  $DELTA u ~=~ ( u sub 2 - u sub 1 ) ^/^ n$

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

In the two-dimensional case, glEvalPoint2, let

$DELTA u ~=~ mark ( u sub 2 - u sub 1 ) ^/^ n$$DELTA v ~=~ mark ( v sub 2 - v sub 1 ) ^/^ m,$where $n$, $u sub 1$, $u sub 2$, $m$, $v sub 1$, and $v sub 2$
  are the arguments to the most recent glMapGrid2 command. Then the glEvalPoint2 command is equivalent to calling

  glEvalCoord2( i$^cdot^DELTA u ~+~ u sub 1$, j$^cdot^DELTA v ~+~ v sub 1$ );The only absolute numeric requirements are that if $i~=~n$,
    then the value computed from $i ^cdot^DELTA u ~+~ u sub 1$ is exactly $u sub 2$, and if $j~=~m$, then the value computed from $i ^cdot^DELTA v ~+~ v sub 1$ is exactly $v sub 2$.

  ## 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(3G) , glEvalMesh(3G) , glMap1(3G) , glMap2(3G) , glMapGrid(3G)

  Table of Contents

  - Name
  - C Specification
  - Parameters
  - Description
  - Associated Gets
  - See Also