CAD export / import bad quality in polygons

Hi guys,

i want to render my PCBs with Keyshot. Therefore i have following work flow:

  1. Using KiCad to create my layouts
  2. Using FreeCad and KiCad StepUp to import the files
  3. Exporting the CAD with tracks as an *.obj
  4. Importing with Keyshot the above mentioned

My problem lies between step 1 and 2. When i import the created layouts i unfortunately get an insufficient result regarding the quality of i.e. the via polygons. This of course results also in a bad result of my renderings. Is there any adjustment which helps me to improve the results so the polygons are much smoother and less edgy?


Best Regards


you may have to ask at FreeCAD forum how to increase obj exporting tesselation.

Sorry i have to correct myself i export it in step

I ran a couple of test and I noticed that StepUp reduces the quality of the copper features in comparison to fcad_kicad (maybe for speed, it definitely runs faster)

fcad running “makeCoppers”


fcad running “make(copper_thickness=0.035, board_thickness=1.53, combo=False)”


StepUp using “AddTracks”

07:20:47  FreeCAD build date: 2021/03/11
07:20:47  STEP UseAppPart available
07:20:52  kicad_parser_version 1.1.7
07:20:52  FC Version 019-24276
07:20:52  tracks version: 1.1
07:20:56  py3
07:20:56  kicad_parser_version 1.1.7
07:37:40  KiCadStepUpWB.Activated(v 10.2.1)

This is exactly my issue but what‘s the solution? I mean i need stepup to import the tracks right? Or how do i use „makeCoppers“?

Fcad_pcb is a FreeCad macro that you can use to import the KiCad pcb directly into FreeCAD. It was initially developed for milling pcbs but has been extended to generate solid modelling of copper features for FEM modelling. You run if from within FreeCAD and it imports the KiCad board file directly.

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Adding to what @John_Pateman said, fcad_kicad only imports the board and models the tracks and vias, without any 3D models for the components on it, the StepUp from @maui uses it internally (AFAIK) to import the copper geometries from the board (tracks, vias, etc.), my assumption is that in order to improve performance, the copper geometry is being simplified by StepUp but I don’t really know it to be true, here maui (the author of StepUp) is the one that knows best.

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great thank you. @maui can you help?

@der.ule if there is no solution for StepUp i installed fcad.

.makeCoppers works perfect but i get an issue if i try the same function as you did. Any idea how to solve this?


First things to take note of:
• Tessellation means different things to the different FreeCad Workbench programmers - not a constant implementation across Workbenches. It changes and evolves with every release version.

• Preferences (FreeCad) are settable once a Workbench is loaded. You’ll need to try different settings to Understand what they do and to dial-in what outcome is best for you…

At present, various pref’s for handling Arcs, Ellipses and Polylines can influence what you see (Graphically and what gets exported for various formats). Multiple settings and panels… Explore them and make a Table for testing them out…

Currently (for me) the best approach when I need smooth Arc’s and Circles is to Plot DXF in Kicad and import into FreeCad. Then, I can ‘Make Face From Wires in the Part workbench (if I want them filled).

Screenshots below
Pads, Via and Traces: Notice the difference in quantity of Line Segments…

I have little access to a PC to check this issue ATM.
An other route could be to export your pcb as vrml and from there export it to obj (both are tesselated sw)

Hi @maui ! Have you had the time to check if somehow the resolution of the copper features is being reduced by KSU? is it something that can be changed in the configuration ?

Hi @der.ule
the code for tracks is based on an early release of fcad_pcb which used polygon instead of arcs.
I have then modified the code to speed up the building process and to reduce the file size…
ATM it is not a simply task to align my code to the latest fcad_pcb release.
I will have a deeper look but it won’t be an immediate solution.

Thanks a lot for the response, that explains the discrepancies. Do not worry, it has zero priority for me, I was just wondering about the differences.

Thanks again for KSU and your continuous push to extend it and improve it! Hands down one of the most useful and feature rich plugin for KiCAD!

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it should be fixed now… (I ported some of the fcad_pcb code)
I also added support for arc tracks and cutting external shape on castellated pads
It shouldn’t be much heavier in file size.


That is great news, thanks a lot!! This seems to me pretty immediate, almost instant! :blush::ok_hand:

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