Some Spherical Boolean Cuts Failing on Cylinder

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akehir
Posts: 1
Joined: Sun May 19, 2019 11:53 am

Some Spherical Boolean Cuts Failing on Cylinder

Postby akehir » Sun May 19, 2019 12:41 pm

Hi,

I'm having some issues making spherical boolean cuts on a cylinder. The problem is, that some cuts seem to be inverted, ie. a wall is being created where it should in fact just make a normal cut.

I found a similar bug / issue here:
https://forum.freecadweb.org/viewtopic.php?t=36090

And one potential workaround, which I will try out next:
https://forum.freecadweb.org/viewtopic.php?t=6814

However, I wanted to ask, what exactly the problem might be, and why some of the boolean cuts work, and others don't (for instance, just re-positioning the sphere seems to sometimes fix the problem).

If I'd understand the root cause, I'd probably be able to avoid the problem. Furthermore, it seems to me that making spherical cuts seems to cause bugs under some conditions?





Freecad Version
OS: macOS 10.14
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16110 (Git)
Build type: Release
Branch: (HEAD detached at 0.18.1)
Hash: f7dccfaa909e5b9da26bf50c4a22ccca9bb10c40
Python version: 3.6.7
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)

(also tried in Windows)


The example files can be found here:
https://akehir.com/cut-operation-1.FCStd
https://akehir.com/cut-operation-2.FCStd

These are how the cuts look for me:

Image
Image
chrisb
Posts: 15624
Joined: Tue Mar 17, 2015 9:14 am

Re: Some Spherical Boolean Cuts Failing on Cylinder

Postby chrisb » Sun May 19, 2019 5:44 pm

I looked at the first file, turning of bottom-ball-hole-003 around the Z-axis solves the problem.

If you face one of these errors, often occurring with coplanar faces, where a tiny move or a rotation fixes a boolean operation there is not much you can do. These are most probably OCC errors. To omit them I only know of the advice to omit coplanar faces.

I would like to add that I hate posts with multiple files attached where I don't know at which file I should look, and which file shows the described behaviour. Less is more.
Attachments
cut-operation-1_cb.FCStd
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Bildschirmfoto 2019-05-19 um 19.43.12.png
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