yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

A bit off-topic, but I'd like to suggest another question : why compute 
non-overlapping volume? It may be justified if you want to compute the 
volume of a cluster, but it is perhaps not relevant if you compute the 
porosity of a confined sphere packing.

Bruno


Václav Šmilauer a écrit :
>  > (1) For tetrahedral elements, I wonder it might be good to use the
>  > polygon boolean operations (there are some example cases in CGAL, 3D
>  > boolean operations, Nef_3), but for spheres I don't have any idea
>
> You can check in trunk:extra/tetra/Tetra.cpp:226 etc, it is exact 4hedra
> intersection code which returns the intersection as union of a number of
> 4hedra (0, 1, or more); I used it a bit and I am reasonably sure that it
> is correct... But the algo is by its nature slow.
>
>
>  > (2) I wonder if opengl has any embedded methods, since it supports
>  > selection the object...
>
> AFAIK core openGL just gives you ray corresponding to the click (i.e.
> ray that is projected as the point you clicked on the screen) and you
> have to find by yourself what objects it intersects. It is drawing lib,
> not geometry lib.
>
>  > (3) More complicated algorithms like ray tracing, etc, but those
>  > algorithms are beyond my area of knowledge.
>  > The reason I think of those methods, is the sampling method (grid
>  > method) is still an approximate method, while polygon boolean
>  > operation is an accurate method..., I might be too critical at this:)
>
> Approximate alogs are tricky in that you have to code also some
> sufficient precision criterion. Otherwise you will have to hardcode very
> fine grid resolution to be reasonable for all corner cases.
>
> Please keep me (us?) posted on what you find out about this. You could
> make a page on wiki on that, too :-)
>
> Vaclav
>
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>   


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Chareyre Bruno
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