GLEVALPOINT(3G)

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
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)