[fixed] Ticket #4001 - Sketcher trimming issue with arcs

[uwestoehr]

I noticed random behavior when trimming arcs in a sketch and think this is a bug.

When trimming 2 intersecting arcs the trimming fails when the endpoint of one arc is coincident with the second arc. Moreover the trimming cannot be undone.

To reproduce open the attached file:

Sketch-cut-problem.FCStd

(3.75 KiB) Downloaded 34 times

and trim the upper ends of the arcs so that only one arc segment would be left. The interesting thing is that the result cannot be foreseen and that in all cases the trimming cannot be undone.
Here is one try:

icmL0Omf4U.gif (507.31 KiB) Viewed 1341 times

but sometimes I end up with 2 arc segments not intersecting each other but being connected in one point.

So am I doing something wrong or is it a bug?

OS: Windows 7
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16110 (Git)
Build type: Release
Branch: (HEAD detached at upstream/releases/FreeCAD-0-18)
Hash: f7dccfaa909e5b9da26bf50c4a22ccca9bb10c40
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: German/Germany (de_DE)

[chrisb]

ping

[abdullah]

So am I doing something wrong or is it a bug?

Of course, it is a bug. I confirm the repeatability.

Please make a ticket in the tracker with a link to the thread so that the file does not get lost.

Trimming relies on a buggy OCCT function. It has been reported to OCCT, but not fixed yet.

There is some code in FreeCAD that tries to compensate for this OCCT bug. Maybe it can be improved to handle this case.

[uwestoehr]

Please make a ticket in the tracker with a link to the thread so that the file does not get lost.

I created now issue #4001.
Many thanks for having a look. Let's cross fingers that the next OCCT release comes soon.

[chrisb]

From my point of view we could well wait for OCC, but it would be great if FreeCAD can handle the undo.

[uwestoehr]

Many thanks abdullah. I can confirm that undo works now fine.

[uwestoehr]

This issue seems to be fixed in OCC 7.4. At least I cannot reproduce the bug anymore.