This tutorial demonstrates how to extract a curve from a surface.
Extraction of curves from a surface sphere by C. Benoit.
To extract a curve defined by x=c on a given surface,
we use the function
P.isoSurfMC.
If a solution is defined on the input surface, it is also defined
in the resulting curves.
If you want to extract the curves defined by a function of x, y, z,
say for instance, x+y = c, you must first defined an intermediate
variable v = x+y in the surface by: b = C.initVars(a, {v} = {CoordinateX}+{CoordinateY}) and use
v in the extraction.
