Resolving Missing Surfaces in FreeCAD

Linux Ubuntu 12.04.1
FreeCAD 0.13 rev 1830 (GR)
OpenCASCADE: libopencascade-ocaf-6.5.0 6.5.0.dsfg-2build1
libopencascade-ocaf-lite-6.5.0 6.5.0.dsfg-2build1

FreeCAD is using the two files listed above. Above an unknown level of complexity, the Boolean operations leave missing surfaces. I'd like to create a bug for bug tracker, but as no one in this forum uses FreeCAD, I'll have to phrase the bug report in a way the OpenCASCADE community will recognize.

The problem occurs when I attempt to perform an operation like this;
1. Select Object A (the part you want to keep)
2. Select Object B (the part you don't want to keep)
3. Subtract Object B from Object A

How do I phrase these operations so the OCC community will recognize them?

Forum supervisor's picture

Dear fester,
Normally you would ask FreeCAD developers to trace the problem down to OCCT and make a fix or at least register the issue in OCCT bug tracker.

On your own, you can try to save (export?) objects A and B to files in BREP format (native to OCCT), and either check the Boolean operation directly in OCCT (if you have it installed) or submit the shapes here for someone else to check.
If the problem is reproduced, and the shapes are valid, then bug on OCCT can be created.
If shapes are bad, you will have to trace back the way how they have been created to identify the root cause.

Note that since OCCT 6.6.0, you can take advantage of automatic check / generation of data for bug reports on BOP.
For that, define environment variable CSF_DEBUG_BOP pointing to some empty directory, and check this directory for the files (BREP shapes and DRAW scripts) which will appear if the algorithm detects a problem.

fester's picture

Have you ever tried the export to BREP?

I selected the two objects in question, then attempted to export to BREP. It didn't work.

There doesn't appear to be any help available for using the Export to Brep command. Do you have any suggestions?

Forum supervisor's picture

Dear fester,
We have tried FreeCAD 0.13 on Windows,
and it seems makes export to BREP quite well (at least a single object).