CGAL users discussion list

[rong tian <>]

I have asked this question one week before but no get answered yet. 

May I post the question here again?

The question is about to find the intersection (polyhedrons) of a cuboid or a cube and a tetrahedron.

I googled and found two most relevant threads discussing the polyhedron intersection. 

One is https://sympa.inria.fr/sympa/arc/cgal-discuss/2012-04/msg00117.html

and the other is http://www.gamedev.net/topic/621717-intersection-of-two-3d-polyhedrons/.

I followed the suggestion by ochyomdu < >, who suggested that

"The easiest way to calculate intersection of two polyhedrons is using of
class Nef_Polyhedron_3.

If You need to use some functions from Polyhedron_3 You can just convert
Polyhedron_3 into Nef_Polyhedron_3 (using constructor), calculate
intersection of polyhedrons and convert the resulting Nef_Polyhedron_3 into
Polyhedron_3 back (using function convert_to_polyhedron()).

Intersection is calculated with operation *
N1*N2
"

I have followed.  The issue is: it works and coding is simple. The only issue is it is slow, and it is VERY slow in my case. I have billions of tetrahedrons to do the intersection test and operation.

My question is since this kind of intersection is sort of special: one is a cuboid and the other is a tetrahedron that is convex. How can I take advantage of those specific geometric features to speed up the intersection? 

Thank you very much for your reading.

Your any hint will be highly appreciated.

Rong

2013/5/5 liudaisuda <>

Linking the dual points of two neighbor incident cells of a vertex is pretty much the same as getting the dual of the corresponding incident edge of that vertex.  Do you have any idea why my approach didn't work ?

On Sun, May 5, 2013 at 10:36 PM, 杨成林 [via cgal-discuss] <[hidden email]> wrote:

Why not just link the dual points of the incident cells?

2013/5/5 liudaisuda <[hidden email]>

I test the code, and for each vertex, it only collected two segments of the
power cell. Therefore, it is clearly incorrect. Anyone has any suggestion
how to achieve my goal?

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Yang Chenglin

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