Round Roof hole creates hollow body and causes 'Not manifold' error

[danyvanimpe-lab]

I may have found a bug related to the Round Roof shape when it is used as a hole.

Steps to reproduce:

Create a solid rectangular block (for example 70 × 50 × 15 mm).
Add some holes or other features (not sure if this is required).
Place a Round Roof on the bottom face.
Set the Round Roof as a hole.
Lower it into the block by only about 1 mm.
Group the objects.

Expected result:

The block remains solid with only a shallow cavity created by the Round Roof.

Actual result:

Section View shows the entire block as hollow.
Split View fails with:
Could not split Group.
Kernel error: Not manifold

Before adding the Round Roof hole, Section View shows the block as a normal solid body. As soon as the Round Roof hole is grouped, the model appears hollow and becomes non-manifold.

I have attached screenshots showing the issue.

Thanks!


Untitled design 32 (2026-10-20 16.39) (2026-10-20 16.37)-bug-report.zip

[henmedia]

@danyvanimpe-lab thank you for the clear steps and the file, it showed the cause. It was not the Round Roof: the third fillet on the pocket (1 mm on five edges) left the block with a mesh that had small gaps at one corner. The body itself was fine, only its triangles did not close. That is why the section view showed it hollow and why the next cut and Split stopped with "Not manifold".

I fixed it: after a fillet or chamfer the mesh is now checked, and one with gaps is rebuilt closed, with the same shape. It comes with the next release. Your saved design keeps the old mesh, so after the update undo that fillet and set it again, then the Round Roof hole and Split work.

[henmedia]

@danyvanimpe-lab the fix for the fillet that left gaps in the mesh is out in 1.95.0: https://github.com/henmedia/layerling/releases/tag/v1.95.0 – a reload of the page brings it. Section view and split should work on your design again.

[danyvanimpe-lab]

Hi Stefan,

Thank you very much for looking into this so quickly.

I tested version 1.95.0 and can confirm that the problem is fixed. Section View and Split now work correctly on my design.

Thank you also for explaining the real cause. I was convinced the Round Roof operation was responsible, so it was interesting to learn that the issue was actually caused by a small mesh gap created by the fillet.

I really appreciate the time you invested in tracking it down and implementing a fix so quickly.

Thanks again for the great support and for all the work you put into Layerling!

[henmedia]

@danyvanimpe-lab thanks for testing it and for the kind words. Your steps and the file made it easy to find, so thank you for that too.