glevalpoint2(3) - Linux man page

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

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