CGAL users discussion list

[Alexander Teibrich <>]

Hi,

I'm looking for a way to enlarge/thicken a non-convex Polyhedron_3 or Nef_polyhedron_3 A by a certain distance x to get B. Basically something like the outset function of inkscape [1]. Scaling alone is not an option, since I have to ensure that B is strictly contained in A.

My current approach is to iterate through all vertices and shift each vertices by x along the vertex normal, that is the average of the normals of all adjoining faces. This works with simple geometries, but quickly leads to self-intersecting faces and invalid Polyhedron_3 / Nef_polyhedron_3 with more complex geometries. Intersecting or overlapping geometries are not strictly a problem, but the geometry has to valid and manifold to be used for future CSG operations.

Shifting A into all possible directions (in 90° or 45° steps) and doing a union operation over all translations would work, but is horribly slow.

Is there a better way to do this?

Thanks!

Alex

[1] https://inkscape.org/en/doc/advanced/tutorial-advanced.html

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Alexander Teibrich

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