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## 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