Problem with intersection

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barnacle
Posts: 12
Joined: Sat Feb 28, 2015 1:51 pm

Problem with intersection

Post by barnacle »

Dear GiD-Team,

I am having some problems with the intersection function. I am programming a TCl script that uses the intersect function. Unfortunately the intersect function is not very reliable. Sometimes after intersecting the two volumes involved are simply gone. This case is however easy to intercept by checking the number of volumes present in the layers involved, slightly changing one of the volumes and repeating the intersection until it works. Just recently, however, another error occured. After intersecting an info window pops up saying: "Volume not closed, surfaces: xxx, xxx". I also want to intercept this error in my tcl script and somehow need a return value from the intersect function I can use.

Thanks for your help,

barnacle
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escolano
Posts: 1918
Joined: Sun Sep 05, 1982 10:51 pm

Re: Problem with intersection

Post by escolano »

You are right, intersections (curve/curve, curve/surface, surface/surface) are a non very robust operation (depending of tolerances and based on numerical algorithms that could non converge).
And it seems that you are trying to do volume boolean operations, that hightly rely in intersection operations, and classification as inside/outside of a point related to a volume.

It is not possible to get a return value of 'GiD_Process' funcions, the stream of words are processed by GiD in a 'unasyncronous' way.

Then I think that there is no easy solution to your question.
I recommend you to avoid the use of this intersection operations when possible (e.g. for particular cases maybe you can calculate this intersection analitically, or do it with another CAD if they are very complicated)

If do you want you can send us simple cases where the intersection fail, in order to improve next GiD Versions.
barnacle
Posts: 12
Joined: Sat Feb 28, 2015 1:51 pm

Re: Problem with intersection

Post by barnacle »

Unfortunate..

However fyi I found a work around. I now check the number of surfaces inside the involved layers before and after the intersection. If the intersection fails due to not closed volumes additional surfaces are created. This way I can capture the error and redo the intersection with slightly changed volumes. Works for me.

Greetings,

barnacle
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