Name
gl.EvalPoint -- generate and evaluate a single point in a mesh
Synopsis
gl.EvalPoint(i[, j])
Function
gl.MapGrid() and gl.EvalMesh() are used in tandem to efficiently generate and evaluate a series of evenly spaced map domain values. gl.EvalPoint() can be used to evaluate a single grid point in the same gridspace that is traversed by gl.EvalMesh(). Calling gl.EvalPoint() with a single argument is equivalent to calling

 
gl.EvalCoord(i*du+u1)

where

 
du = (u2-u1)/n

and n, u1, and u2 are the arguments to the most recent gl.MapGrid() command. The one absolute numeric requirement is that if i = n, then the value computed from i*du+u1 is exactly u2.

In the two-dimensional case, gl.EvalPoint(), let

 
du = (u2-u1)/n
dv = (v2-v1)/m

where n, u1, u2, m, v1, and v2 are the arguments to the most recent gl.MapGrid() command. Then the gl.EvalPoint() command is equivalent to calling

 
gl.EvalCoord(i*du+u1, j*dv+v1)

The only absolute numeric requirements are that if i = n, then the value computed from i*du+u1 is exactly u2, and if j = m, then the value computed from j*dv+v1 is exactly v2.

Please consult an OpenGL reference manual for more information.

Inputs
i
specifies the integer value for grid domain variable i
j
optional: specifies the integer value for grid domain variable j
Associated gets
gl.Get() with argument #GL_MAP1_GRID_DOMAIN

gl.Get() with argument #GL_MAP2_GRID_DOMAIN

gl.Get() with argument #GL_MAP1_GRID_SEGMENTS

gl.Get() with argument #GL_MAP2_GRID_SEGMENTS


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