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glEvalPoint1, glEvalPoint2 - generate and evaluate a single point
in a mesh
void glEvalPoint1( GLint i )
void glEvalPoint2( GLint i,
GLint j )
eqn not supported
- i
- Specifies the integer value for grid domain
variable $i$.
- j
- Specifies the integer value for grid domain variable $j$
(glEvalPoint2 only).
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
$v sub 2$.
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
glEvalCoord(3G)
, glEvalMesh(3G)
,
glMap1(3G)
, glMap2(3G)
, glMapGrid(3G)
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