CGAL users discussion list

[khaldon hmesheh <>]

thank you for reply

From: Henrik Zimmer <>
To:
Sent: Tuesday, October 8, 2013 9:15 PM
Subject: Re: [cgal-discuss] 3D Identity

>The actual 1mm test could be quite costly to compute if you have fine
>tessellations. But it could be possible to use a two-sided hausdorff
>distance as already suggested.
What is meant hier with two-sided hausdorff distance? (any papers, Websites etc..)


>Now, even if a 3d shape descriptor does not completely solve your
>problem, you could still use some (efficient) descriptor as a pre-test,
>and only if the shapes are "similar enough" you switch to the actual
>test for the 1mm distance.
Which (effecient) descriptors did you mean?
I have used for example Shape distribution which is quite easy to implement, but the result itself is not quite descriptive and discriminative

>By the way, does "identical" include orientation and scale?
No, I want to decide just if the two parts are geometric identical. (one to one independent from the position in space)
The parts may lie freely in the 3d space and I search some ways not to tackle with such problems

>One suggestion could be to use the concavity-based descriptors in [1]
>which are "invariant" to tessellation, orientation and scale.
>(and the scale-invariance could be disabled by removing the
>normalization)
>There is source code available, which is already partly implemented
>using CGAL.
very nice job, is that result quite satisfactory? I mean the result is 100% precise

Hope it helps

[1] http://www.rwth-graphics.de/software/spc


On Do, 2013-10-03 at 02:48 -0700, khaldon hmesheh wrote:
> Thanks for reply
>       
>        ______________________________________________________________
>        From: Laurent Rineau (CGAL/GeometryFactory)
>        <>
>        To: "" <>
>        Sent: Thursday, October 3, 2013 10:55 AM
>        Subject: Re: [cgal-discuss] 3D Identity
>       
>       
>        Le jeudi 03 octobre 2013 01:43:37 khaldon hmesheh a écrit :
>        > Hello,
>        >
>        > I am searching for some algorithms to check if two 3D
>        triangulated Shapes
>        > are identical. See attachement. Any suggestions or help.
>       
>        >Search the web for "3d shape descriptors". There are a lot of
>        articles! On the
>        >other hand, that also means that the subject is not fully
>        solved with a single
>        >solution that fits all needs.
>       
>        I searched for such algorithms but as you said it is not fully
>        solved and my problem is to decide if two parts are identical
>        for tolerances less than 1mm.
>       
>        >Anyway, there is nothing ready to use in CGAL, as far as I
>        know, but you can
>        >use CGAL to implement any algorithm found in one of the
>        articles on the
>        >subject.
>       
>       
>        >With a second though, it seems that your problem may be more
>        simple that the
>        >general shape recognition. You could use the AABB Tree from
>        CGAL to compute
>        >the Haussdorf between your two surfaces, and decide that they
>        are sufficiently
>        >similar if that distance is lower that a given bound.
>       
>        I have applied Fréchet distance  for 2D shapes and it returned
>        a very satisfactory result.
>        But I never used for 3D shapes.  You mean that Hausdorff
>        Distance is also applicable for 3D surfaces.
>       
>        --
>        Laurent Rineau, PhD
>        R&D Engineer at GeometryFactory
>        http://www.geometryfactory.com/
>        Release Manager of the CGAL Project      http://www.cgal.org/
>       
>       
>        --
>        You are currently subscribed to cgal-discuss.
>        To unsubscribe or access the archives, go to
>        https://sympa.inria.fr/sympa/info/cgal-discuss
>       
>       
>       
>       
>       



--
You are currently subscribed to cgal-discuss.
To unsubscribe or access the archives, go to
https://sympa.inria.fr/sympa/info/cgal-discuss