Different object amount in same layer using FreeCAD and LibreDWG

[giedrius-N]

Hello,

I encountered an issue where the number of objects read from a DWG file using LibreDWG does not match the number of objects visible in FreeCAD. Specifically, when I open the same DWG file in FreeCAD, I get fewer objects than what LibreDWG reads in that particular layer. My application reads extra objects, which I suspect are unwanted lines or polylines.

• In FreeCAD, I see only 14 objects in a particular layer, which is correct.
• When I use LibreDWG to parse the same file, I get 26 objects in the same layer, which includes 12 extra simple lines and polylines that should not exist.

These extra objects appear in specific layers and show up in the left corner of the drawing. This behavior is incorrect because they are not present in FreeCAD, and they should not be there according to the original file.

Things I’ve tried:

• I’ve confirmed that all layers are visible in FreeCAD, and nothing is hidden. So, the extra objects are definitely not on hidden layers.
• I checked for blocks or nested elements in the DWG file that could contain these extra lines/polylines, but nothing seems out of place in FreeCAD.
• I attempted to clean up the file and remove any redundant objects, but this did not change the outcome when opening the file in LibreDWG.

Questions

• Why might LibreDWG be interpreting these extra lines and polylines, while FreeCAD does not show them?
• How can I reliably filter out or ignore these unwanted objects in my program? Are there any specific flags or properties in DWG objects that LibreDWG is reading, which FreeCAD might be ignoring?
• Could this be related to block definitions or some kind of auxiliary geometry that FreeCAD hides by default? If so, how should I handle these cases programmatically?

Those above in red rectangle are unwanted objects.
In second image there is what I see in FreeCAD

Any help or guidance would be greatly appreciated! Thanks in advance!

[michal-josef-spacek]

As I understand, FreeCAD uses different approaches to read DWG files (libredwg dwg2dxf or ODA converter or qcad) to convert to DXF.

Some hints:

1. Test on DXF file.
2. Check which one of the converters is used.