Facebinder faces changes randomly

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paullee
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Facebinder faces changes randomly

Postby paullee » Thu Feb 23, 2017 5:40 pm

Hi, I am further exploring new commit for adding/editing faces which is terrific! Thanks Yorik!

I find a problem which I am not sure if it is a bug or not.

The faces of the facebinder change randomly when I change some parameters of the underlying object for facebinder - even I do not change the topology of the underlining object.

For example, I have a cube, 'thickness' it, select some faces in facebinder. Now, I change the length - then different faces come up!?

I have a fcstd attached below, slightly more complicated only
- one with 'thickness' of cube in arc
- one with 'thickness' of exactly the same cube in 'intersection' (i.e. not fillet in edge): this rectangular object seem slightly more stable
[ however, when I try in my building facade model, a facebinder come up with random faces after some changes in underlying object]



Screenshot from 2017-02-24 01-21-41.png
Screenshot from 2017-02-24 01-21-41.png (223.84 KiB) Viewed 354 times


Screenshot from 2017-02-24 01-17-13.png
Screenshot from 2017-02-24 01-17-13.png (229.14 KiB) Viewed 354 times

Screenshot from 2017-02-24 01-19-36.png
Screenshot from 2017-02-24 01-19-36.png (236.49 KiB) Viewed 354 times

Screenshot from 2017-02-24 01-18-33.png
Screenshot from 2017-02-24 01-18-33.png (236.76 KiB) Viewed 354 times


Test_ Facebinder & Envelope _ Add Face _OK.fcstd
(117.35 KiB) Downloaded 6 times




(Also tested with same result in FreeCAD-0.17.git201701202112.glibc2.17-x86_64.AppImage]

[ freecad-0.17_pre-10236.x86_64 - przemof-FreeCAD.repo ]

OS: Linux
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.10236 (Git)
Build type: Unknown
Branch: master
Hash: dd20ba3d068c4a0903417d93144f8ac7fed068e9
Python version: 2.7.13
Qt version: 4.8.7
Coin version: 3.1.3
OCC version: 6.8.0.oce-0.17
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yorik
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Re: Facebinder faces changes randomly

Postby yorik » Sat Feb 25, 2017 4:21 pm

This is an inherent problem of OpenCasCade, FreeCAD's geometry engine. Each time a shape is generated, the order of faces is unpredictable. So when the facebinder uses for ex. face n°1 of underlying shape, the face n°1 can be another when the underlying shape will be recomputed. Several areas of FreeCAD suffer from that problem.

Unfortunately it is an extremely difficult problem to solve. Many tried already, but with no success so far...
paullee
Posts: 88
Joined: Wed May 04, 2016 3:58 pm

Re: Facebinder faces changes randomly

Postby paullee » Sun Feb 26, 2017 12:57 am

yorik wrote:This is an inherent problem of OpenCasCade, FreeCAD's geometry engine. Each time a shape is generated, the order of faces is unpredictable. So when the facebinder uses for ex. face n°1 of underlying shape, the face n°1 can be another when the underlying shape will be recomputed. Several areas of FreeCAD suffer from that problem.

Unfortunately it is an extremely difficult problem to solve. Many tried already, but with no success so far...


I see....

So anybody has an idea how Part Thickness is able to work with that? It needs to pick 1 or more faces to create a hollow / pipe like object.

I think ... so far I had explored about it ... the resulted objects did not change the face it was originally picked.

Thanks.
paullee
Posts: 88
Joined: Wed May 04, 2016 3:58 pm

Re: Facebinder faces changes randomly

Postby paullee » Sun Feb 26, 2017 3:58 am

I mean Part Thickness seems do not have problem when the underlying object change e.g. in its width, length, height etc.
Joyas
Posts: 287
Joined: Sat Jul 12, 2014 8:39 pm

Re: Facebinder faces changes randomly

Postby Joyas » Sun Feb 26, 2017 5:09 pm

paullee wrote:
yorik wrote:This is an inherent problem of OpenCasCade, FreeCAD's geometry engine. Each time a shape is generated, the order of faces is unpredictable. So when the facebinder uses for ex. face n°1 of underlying shape, the face n°1 can be another when the underlying shape will be recomputed. Several areas of FreeCAD suffer from that problem.

Unfortunately it is an extremely difficult problem to solve. Many tried already, but with no success so far...


I see....

So anybody has an idea how Part Thickness is able to work with that? It needs to pick 1 or more faces to create a hollow / pipe like object.

I think ... so far I had explored about it ... the resulted objects did not change the face it was originally picked.

Thanks.

It depends on many things: order of operations, number of faces...
I prefer JavaScript, I don't like Python indentation.
HoWil
Posts: 371
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Location: Austria

Re: Facebinder faces changes randomly

Postby HoWil » Thu Mar 09, 2017 7:54 am

Hello,
The related keyword.... Topological naming is discussed here https://forum.freecadweb.org/viewtopic. ... opological

Maybe a tool to get faces and solid at specific coordinates could solve the problem.

BR,
Howil
paullee
Posts: 88
Joined: Wed May 04, 2016 3:58 pm

Re: Facebinder faces changes randomly

Postby paullee » Fri Mar 10, 2017 12:08 am

HoWil wrote:Hello,
The related keyword.... Topological naming is discussed here https://forum.freecadweb.org/viewtopic. ... opological



I hope it can be resolved in facebinder since I have some trials and thought it would be helpful on architectural modeling ^^

I had used, as i mentioned Thickness, which seem do not suffer from this problem - but the models itself is much complicated and larger than a solution with facebinder!
HoWil
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Location: Austria

Re: Facebinder faces changes randomly

Postby HoWil » Fri Mar 10, 2017 6:58 am

Dear paullee,

I opended your model and it was not entirely sure that I do understand what you want to achieve.

I see two times the use of thickness/wall and several Facebinder objects.

Do you have some picture about the piece you want to draw. Did you consider using Part-Design-Next .... there you have a more structured model-tree so it is (for me) easier to understand what is done first and how the "production" steps are arranged.

BR,
HoWil
paullee
Posts: 88
Joined: Wed May 04, 2016 3:58 pm

Re: Facebinder faces changes randomly

Postby paullee » Fri Mar 10, 2017 11:46 am

HoWil wrote:Dear paullee,

I opended your model and it was not entirely sure that I do understand what you want to achieve.

I see two times the use of thickness/wall and several Facebinder objects.

Do you have some picture about the piece you want to draw. Did you consider using Part-Design-Next .... there you have a more structured model-tree so it is (for me) easier to understand what is done first and how the "production" steps are arranged.



Thanks!

The file I produced here originally is intended to test how facebinder works (after Yorik recently add features to it). [ But I find it is not stable somehow as discussed above somehow ... ]

The original idea is originated from modeling building, trying to build external surfaces / faces or cladding on the building facades. I was originally testing Thickness which works somehow. You may have a look at discussion and problem, models and images I posted after discussion between Rockn and Yorik on Architectural Cladding - https://forum.freecadweb.org/viewtopic.php?f=23&t=5023.

In short, I want to render a building. Usually, different surface of a building may come with different colour, cladding, texture even it may be same wall in the model (or internal face of a wall be plaster and paint, whilst external be tiles or cladding etc etc.) So the intention is to model a building in solid, then single out those wall surfaces from the model, and group them according to their materials and texture type.

Then, it may help for export to Blender for rendering. I am testing if this procedures works but it seem facebinder has problem if I need to update the underlying model.