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glEvalPoint.3gl

NAME

glEvalPoint1, glEvalPoint2 - generate and evaluate a single point in a mesh

C SPECIFICATION

void glEvalPoint1( GLint i )

void glEvalPoint2( GLint i,

 
                      GLint j )
 

delim $$

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)