# glEvalPoint

generate and evaluate a single point in a mesh

## Signature

glEvalPoint( )->
glEvalPoint1( GLint ( i ) )-> void
glEvalPoint1( )
glEvalPoint2( GLint ( i ) , GLint ( j ) )-> void
glEvalPoint2( i , )

## Parameters

VariablesDescription
i
Specifies the integer value for grid domain variable $\mathit{i}$ .
j
Specifies the integer value for grid domain variable $\mathit{j}$ ( 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( $i\mathit{u}+{\mathit{u}}_{1}$ ); );
where
$\mathit{u}=\frac{\left({\mathit{u}}_{2}-{\mathit{u}}_{1}\right)}{\mathit{n}}$
and $\mathit{n}$ , ${\mathit{u}}_{1}$ , and ${\mathit{u}}_{2}$ are the arguments to the most recent glMapGrid1 command. The one absolute numeric requirement is that if $\mathit{i}=\mathit{n}$ , then the value computed from $\mathit{i}\mathit{u}+{\mathit{u}}_{1}$ is exactly ${\mathit{u}}_{2}$ .
In the two-dimensional case, glEvalPoint2 , let
$\mathit{u}=\frac{\left({\mathit{u}}_{2}-{\mathit{u}}_{1}\right)}{\mathit{n}}$
$\mathit{v}=\frac{\left({\mathit{v}}_{2}-{\mathit{v}}_{1}\right)}{\mathit{m}}$
where $\mathit{n}$ , ${\mathit{u}}_{1}$ , ${\mathit{u}}_{2}$ , $\mathit{m}$ , ${\mathit{v}}_{1}$ , and ${\mathit{v}}_{2}$ are the arguments to the most recent glMapGrid2 command. Then the glEvalPoint2 command is equivalent to calling
glEvalCoord2( $i\mathit{u}+{\mathit{u}}_{1},j\mathit{v}+{\mathit{v}}_{1}$ ); );
The only absolute numeric requirements are that if $\mathit{i}=\mathit{n}$ , then the value computed from $\mathit{i}\mathit{u}+{\mathit{u}}_{1}$ is exactly ${\mathit{u}}_{2}$ , and if $\mathit{j}=\mathit{m}$ , then the value computed from $\mathit{j}\mathit{v}+{\mathit{v}}_{1}$ is exactly ${\mathit{v}}_{2}$ .

## 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