GLEVALPOINT(3G)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 )
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 ALSOglEvalCoord(3G), glEvalMesh(3G), glMap1(3G), glMap2(3G), glMapGrid(3G)
March 1, 2011