glEvalPoint1,
glEvalPoint2
[New
- Windows 95, OEM Service Release 2]
The glEvalPoint1
and glEvalPoint2 functions generate and evaluate a single point in a
mesh.
void glEvalPoint1(
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GLint i |
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); |
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void glEvalPoint2(
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GLint i, |
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|
GLint j |
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); |
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Parameters
i
The integer
value for grid domain variable i.
j
The integer
value for grid domain variable j (glEvalPoint2 only).
Remarks
The glMapGrid and glEvalMesh functions are used in
tandem to efficiently generate and evaluate a series of evenly spaced map
domain values. You can use glEvalPoint to evaluate a single grid point
in the same gridspace that is traversed by glEvalMesh. Calling glEvalPoint1
is equivalent to calling
glEvalCoord1(i Du + u (1) );
where
Du = (u (2) - u (1) ) / n
and n,
u (1) , and u
(2) are the arguments to the most recent glMapGrid1
function. The one absolute numeric requirement is that if i = n,
then the value computed from i D u + u (1) is exactly u (2) .
In the
two-dimensional case, glEvalPoint2, let
Du = (u (2) - u (1) )/n
Dv = (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
function. Then the glEvalPoint2 function is equivalent to calling
glEvalCoord2(i Du + u (1) , j Dv + v (1) );
The only
absolute numeric requirements are that if i = n, then the value
computed from i Du + u (1) is exactly u (2) , and if j
= m, then the value computed from j Dv + v (1) is exactly v (2) .
The following
functions retrieve information relating to glEvalPoint1 and glEvalPoint2:
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