Name
glEvalPoint — 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
·
Δ
u
+
u
1
);
where
Δ
u
=
u
2
-
u
1
n
and
n,
u
1
,
and
u
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
·
Δ
u
+
u
1
is exactly
u
2
.
In the two-dimensional case, glEvalPoint2, let
Δ
u
=
u
2
-
u
1
n
Δ
v
=
v
2
-
v
1
m
where
n,
u
1
,
u
2
,
m,
v
1
,
and
v
2
are the arguments to the most recent glMapGrid2 command.
Then the glEvalPoint2 command is equivalent to calling
glEvalCoord2(
i
·
Δ
u
+
u
1
,
j
·
Δ
v
+
v
1
);
The only absolute numeric requirements are that if
i
=
n
,
then the value computed from
i
·
Δ
u
+
u
1
is exactly
u
2
,
and if
j
=
m
,
then the value computed from
j
·
Δ
v
+
v
1
is exactly
v
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
Copyright
Copyright © 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.