Part - create solid, alternative that doesn't increase the tolerance?

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MRx
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Part - create solid, alternative that doesn't increase the tolerance?

Post by MRx »

Hi,

I somewhat suspect that Part - create solid is increasing the tolerance of an object whenever it is needed in order to sew a shell together.
Is there any better way to do that?
Increasing the tolerance of various items (edges, vertices) is potentially harmful to an object - and I ran into that several times in the past.
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Vincent B
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Re: Part - create solid, alternative that doesn't increase the tolerance?

Post by Vincent B »

There are a tool to increase tolerance:
https://wiki.freecadweb.org/OpenSCAD_In ... nceFeature
but I afraid we can't decrease it anymore.
MRx
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Re: Part - create solid, alternative that doesn't increase the tolerance?

Post by MRx »

The question is how to keep the tolerance low instead of increasing it ... increasing it too much is calling for problems sooner or later.
There's the python method fixTolerance which someone can run, with checkgeometry violating edges / vertexes can be found.

I fixed the particular object myself by duplicating edges at the joints and removing the so called "generated" edge which was responsible for increasing the tolerance.
Maybe I should have a closer look at the drafts operations if there's an issue.

It's an opencascade topic.
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onekk
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Re: Part - create solid, alternative that doesn't increase the tolerance?

Post by onekk »

MRx wrote: Sun Nov 27, 2022 9:28 pm Hi,

I somewhat suspect that Part -...
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GeneFC
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Re: Part - create solid, alternative that doesn't increase the tolerance?

Post by GeneFC »

MRx wrote: Sun Nov 27, 2022 9:28 pm increasing the tolerance of an object whenever it is needed
Are you suggesting that the tolerance is increased when it is not needed?

Seems like the alternative to this behavior is that the process fails. Is that what you want?

Your "fix" is a patch-up that only you can decide. It would be hard for a program to know what edges to duplicate without making a larger mess.

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MRx
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Re: Part - create solid, alternative that doesn't increase the tolerance?

Post by MRx »

Well this is something for opencascade, the best case would be to stay within a given tolerance and tie the vertexes together (copy the same values -- if wanted).
I isolated the part where the tolerance went high again and re-designed that part in a new project, the redesigned Part does not show any issues.
A feature that would be definitely nice would be to re-create an object and alter the coordinates according to some given parameters, the opencascade options within the draft workbench are good but still not enough for that.

A too high tolerance just leads to many problems, I start to think that my object went bad due to a bug within an older freecad version (the object has a long history).
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Re: Part - create solid, alternative that doesn't increase the tolerance?

Post by GeneFC »

MRx wrote: Tue Nov 29, 2022 6:44 am Well this is something for opencascade, the best case would be to stay within a given tolerance and tie the vertexes together
This sounds completely unworkable. You are now requiring two tolerances settings, one for the "tolerance" and one for the emergency "tie the vertexes together".

Hint: Not all close vertices should be tied together. :?

The old computer adage GIGO would seem to apply here. Supply quality input and the problem does not arise.

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Re: Part - create solid, alternative that doesn't increase the tolerance?

Post by MRx »

Hint: Not all close vertices should be tied together. :?
I agree, I have seen all the issues that can happen with tolerance issues.

Visually the object looks okay - so in that case all the vertices which look like as if they're joining should be able to join by copying either vertex coordinate A, B or interpolate both of them.
I will have have a closer look at that within the next days and try to iterate through the object to see if something like that is possible.

Please correct me if my assumption is wrong, or if I'm missing something.
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