[Possible bug] FreeCAD reports multiple solids for single solid body.

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tadeuszd
Posts: 20
Joined: Wed Nov 02, 2022 9:23 pm

[Possible bug] FreeCAD reports multiple solids for single solid body.

Post by tadeuszd »

Hi,
I encountered strange FreeCAD behavior for body with elliptical curves.
I created simple body - just 2 revolutions and 1 pad, all mirrored. All features keeps solid body. The yellow ellipse is the Sketch001. This is the base sketch for Pad. To create correct element, this sketch should be shifted to x = -50,00 mm. But for this value the body disappears and FreeCad throws warning message:
"Transformed: Result has multiple solids. Only keeping the first."
If you set x = -49,99 mm, FreeCAD throws error:
"Recompute failed! Please check report view."
But if you shift Sketch001 to x = -49,90 mm or x = 50,10 mm FreeCAD doesn't reports any errors and the body looks correct (except incorrect shift).

First time I encountered described behavior in my project. To eliminate any problems with my project, I redraw whole body from the scrratch, but the problem appears again.

Can anybody explain me, what is wrong?

Code: Select all

OS: Windows 7 Version 6.1 (Build 7601: SP 1)
Word size of FreeCAD: 64-bit
Version: 0.21.31097 (Git)
Build type: Release
Branch: master
Hash: ccf074008774f1bdfed8fec09ed60e2c0fe77cae
Python 3.8.15, Qt 5.15.4, Coin 4.0.0, Vtk 9.1.0, OCC 7.6.3
Locale: Polish/Poland (pl_PL)
Attachments
Test-ellipses.FCStd
(326.95 KiB) Downloaded 13 times
Test-ellipses2.png
Test-ellipses2.png (63.49 KiB) Viewed 703 times
Test-ellipses1.png
Test-ellipses1.png (102.17 KiB) Viewed 703 times
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Shalmeneser
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Location: Fr

Re: [Possible bug] FreeCAD reports multiple solids for single solid body.

Post by Shalmeneser »

:idea:
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Test-ellipses_SHALM.FCStd
(22.64 KiB) Downloaded 13 times
Capture du 2022-11-25 22-21-35.png
Capture du 2022-11-25 22-21-35.png (57.74 KiB) Viewed 665 times
chrisb
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Re: [Possible bug] FreeCAD reports multiple solids for single solid body.

Post by chrisb »

It is probably one of these coplanar issues, where Part workbench fails with an invalid object. There is not much you can do different from what you already did. Some rounding errors depend on the orientation, sou you can try to build this based on one of the other main planes.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
chrisb
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Re: [Possible bug] FreeCAD reports multiple solids for single solid body.

Post by chrisb »

Shalmeneser wrote: Fri Nov 25, 2022 9:22 pm:idea:
I had also playd with this approach, but I could not create the elliptical part of the tube.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
tadeuszd
Posts: 20
Joined: Wed Nov 02, 2022 9:23 pm

Re: [Possible bug] FreeCAD reports multiple solids for single solid body.

Post by tadeuszd »

Shalmeneser wrote: Fri Nov 25, 2022 9:22 pm:idea:
Thanks a lot, but it is not solution. Some fragments in my body are ellipstical. :roll:
chrisb wrote: Fri Nov 25, 2022 9:27 pm It is probably one of these coplanar issues, where Part workbench fails with an invalid object. There is not much you can do different from what you already did. Some rounding errors depend on the orientation, sou you can try to build this based on one of the other main planes.
I tested today many configurations and I am almost sure that problem lies in elliptical fragments in sketches. I have also significant problems with element presented in post https://forum.freecadweb.org/viewtopic. ... 25#p643525 . I also used many ellipses to create it and FreeCAD crashes when I try to expand this element with other features - simple pads, for example.

For now I replaced all ellipses in sketches with sets of arcs (ellipse emulation). And now everything works fine! I didn't change anything else.
It means, if the problem lies in "rounding errors", it affects the elliptical curves in extremely significant way.

Tadeusz
Attachments
Test-ellipses-good.png
Test-ellipses-good.png (80.63 KiB) Viewed 539 times
Test-ellipses-good2.png
Test-ellipses-good2.png (23.37 KiB) Viewed 539 times
chrisb
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Re: [Possible bug] FreeCAD reports multiple solids for single solid body.

Post by chrisb »

Just for your information: I created an ellipse from two elliptical arcs, so that the seam didn't coincide with one of the others. It didn't work either.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
tadeuszd
Posts: 20
Joined: Wed Nov 02, 2022 9:23 pm

Re: [Possible bug] FreeCAD reports multiple solids for single solid body.

Post by tadeuszd »

chrisb wrote: Sun Nov 27, 2022 8:55 am...It didn't work either.
Hi,
Please look at completely messed up structure of vertices and edges in body created using ellipses (upper model). For comparison - nice mesh of body created only with arcs (lower model).
Similar structure (but not so messed up) is created by complex transformations like lofts and pipes. It suggest, that FreeCAD doesn't recognise ellipse as basic/elementary shape. Is it true?
Attachments
Test-ellipses-3.FCStd
(116.84 KiB) Downloaded 8 times
Test-ellipses-3.png
Test-ellipses-3.png (77.8 KiB) Viewed 419 times
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