GLEVALPOINT(3G) OpenGL Manual GLEVALPOINT(3G)
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
.
/
u
+
u
1
);
where / 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 . / u + u 1 is exactly u 2.
In the two-dimensional case, glEvalPoint2, let
/ u = u 2 - u 1 n.PP / 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
.
/
u
+
u
1
,
j
.
/
v
+
v
1
);
The only absolute numeric requirements are that if i = n, then the value computed from i . / u + u 1 is exactly u 2, and if j = m, then
the value computed from j . / 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
SEE ALSO
glEvalCoord(), glEvalMesh(), glMap1(), glMap2(), glMapGrid()
COPYRIGHT
Copyright (C) 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/.
AUTHORS
opengl.org
opengl.org 06/10/2014 GLEVALPOINT(3G)
