glevalPoint生成及求解一个网格中的单点
glevalPoint生成及求解一个网格中的单点
glevalPoint1, glevalPoint2 - generate and evaluate a single point in a mesh
C SPECIFICATION
void glevalPoint1( GLint i )
void glevalPoint2( GLint i, GLint j )
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 ?Δu + u1);
where
Δu = (u2 - u1 ) / n
and n, u1, and u2 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 ?Δu + u1 is exactly u2.
In the two-dimensional case, glevalPoint2, let
Δu = (u2 - u1 )/n
Δv = (v2 - v1 )/m
where n, u1, u2, m, v1, and v2 are the arguments to the most recent glMapGrid2 command. Then the glevalPoint2 command is equivalent to calling
glevalCoord2(i ?Δu + u1, j ?Δv + v1);
The only absolute numeric requirements are that if i = n, then the value computed from i ?Δu + u1 is exactly u2, and if j = m, then the value computed from j ?Δv + v1 is exactly v2.
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"
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