Issues with STEP file import

[bdeimen]

Description of the bug

Some STEP files end up creating faceted faces instead of curves when imported. I'm specifically referring to the large triangular face on the right side of the first image. It is replicated around the model. I haven't been able to identify what causes the difference. It happened between two different version exports of the same model.

Project file & How to reproduce

STEPBugProjects.zip

Checklist of files included above

• Project file
• Screenshot

Version of PrusaSlicer

Version 2.9.0

Operating system

Windows

Printer model

Ender 3 Pro

[bdeimen]

I have re-imported the step file into Fusion and the curves seem to be intact.

[kubispe1]

The way PrusaSlicer handles STEP files is by tessellating the model during import. Tessellation converts the smooth surfaces and curves from the STEP file into a mesh of polygons (typically triangles), which are then used for slicing. This process can sometimes result in faceted faces instead of smooth curves.

[bdeimen]

That may be the case, but this is still clearly a bug in that process. The same model with only slight alterations imports without the extreme faceting that this one is causes. Additionally, converting it to a mesh/tessellating it in Fusion doesn't cause this issue.

[bdeimen]

Here's another image to clarify what I'm taking issue with:

[aknezevi-work]

Yes, it would be extremely beneficial to have an option to choose import parameters.

Bambu Studio, which was original from which STEP format importing was ported, according to Prusa, has options to choose the quality of import: https://wiki.bambulab.com/en/software/bambu-studio/step