CGAL users discussion list

[Guillaume Damiand <>]

Le 06/11/2012 18:18, johnzjq a écrit :
> Is there any simpler solution to it, without knowing the global knowledge
> about the polyhedron?

Orientation is a global property.
Indeed, you can build two objects having exactly a same local 
configuration but with two opposite orientations.

To orient correctly a polyhedron, you can take a face with a given 
orientation, compute its normal, take a point in the face, translate it 
along the normal, and test if this point is inside or outside to the 
polyhedron (counting the number of intersections of a half-line starting 
from the point and the polyhedron).
Depending on which orientation you want, you conclude if the initial 
orientation is correct or wrong; then you propagate the correct 
orientation to all the faces of the polyhedron.

Guillaume


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