2-manifold slicing

[Petr Felkel]

I need to construct the contours in cross-sections from the input
triangular surface mesh (to slice the surface). It looks like a typical
CAD problem, byt I can't find either literature about this topic either
any publicly available source code.

The mesh is given as an indexFaceSet (in VRML), that means by the list
of points and by the list of tripples of indices, one tripple for one
triangle. The triangles are counter-clockwise oriented (their normal is
directed out from the surface). 

The created contours have to be also oriented - counter-clockwise for
the surface and clockwise for the holes (the inner part of object is on
the left-hand side of the contour.

The original mesh has been created by contour tiling - i.e. the major
number of triangles have one edge parallel to the cutting plane. But
there are mesh nodes (X) between the original cross-sections also, and
they complicate the slicing. 

Simple slicing  between planes which doesn't go through the (X) points
looks simple - I need to compute two intersections of two triangle edges
and then connect the segments into contours. The edge is shared by
exactly two triangles and the segment connectivity computation is
simple. But the singular cases exist, when the cross-section goes
through the (X) mesh node. More triangles complicates the intersection
computations and the problem of detection of the segment connectivity.

I will be grateful for any help

Thank you in advance 

	Petr Felkel
        felkel at sgi.felk.cvut.cz


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