Global-only top surface detection breaks functional planar surfaces #945

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MrUnknownDE · 2026-04-05T16:36:56+02:00

MrUnknownDE commented

2026-04-05 16:36:56 +02:00

Originally created by @Diavolo73 on 1/28/2026

Is there an existing issue for this feature request?

I have searched the existing issues

Description

Bambu Studio (and OrcaSlicer) only detect top surfaces globally per Z-layer.
If any geometry exists above a given layer, no area of that layer is treated as a top surface.

This causes large planar, visible, and functionally critical surfaces to be sliced as internal skin instead of top surfaces.

Why this is a problem

This behavior leads to:

open extrusion line ends

missing surface finishing logic

poor layer fusion

leakage on sealing surfaces

This is not a cosmetic issue but a functional failure for parts requiring airtight or fluid-tight surfaces (e.g. filter housings).

Reproducibility

Geometry is valid and dimensionally correct

Large planar surface exists

Small features (pins, bosses) extend above the same Z-layer

Slicer refuses to apply top-surface logic to any part of the layer

Comparison

Ultimaker Cura correctly handles this case using local top-surface detection, allowing different surface types within the same layer.

This demonstrates that the limitation is architectural, not geometrical.

Expected behavior

Local top surfaces should be detected independently

A layer may contain both top surfaces and non-top surfaces

Surface classification should be visibility-based, not global

Impact

This limitation makes Bambu Studio unsuitable for printing functional parts with sealing or flow-critical surfaces, despite excellent hardware quality.

Conclusion

Please consider implementing local top-surface segmentation.
This is a critical feature for professional and functional use cases.

Which printers will be beneficial to this feature?

All

Describe the solution you'd like

Please consider implementing local top-surface segmentation.
This is a critical feature for professional and functional use cases.

Describe alternatives you've considered

Cura

Additional context

*Originally created by @Diavolo73 on 1/28/2026* ### Is there an existing issue for this feature request? - [x] I have searched the existing issues ### Is your feature request related to a problem? Description Bambu Studio (and OrcaSlicer) only detect top surfaces globally per Z-layer. If any geometry exists above a given layer, no area of that layer is treated as a top surface. This causes large planar, visible, and functionally critical surfaces to be sliced as internal skin instead of top surfaces. Why this is a problem This behavior leads to: open extrusion line ends missing surface finishing logic poor layer fusion leakage on sealing surfaces This is not a cosmetic issue but a functional failure for parts requiring airtight or fluid-tight surfaces (e.g. filter housings). Reproducibility Geometry is valid and dimensionally correct Large planar surface exists Small features (pins, bosses) extend above the same Z-layer Slicer refuses to apply top-surface logic to any part of the layer Comparison Ultimaker Cura correctly handles this case using local top-surface detection, allowing different surface types within the same layer. This demonstrates that the limitation is architectural, not geometrical. Expected behavior Local top surfaces should be detected independently A layer may contain both top surfaces and non-top surfaces Surface classification should be visibility-based, not global Impact This limitation makes Bambu Studio unsuitable for printing functional parts with sealing or flow-critical surfaces, despite excellent hardware quality. Conclusion Please consider implementing local top-surface segmentation. This is a critical feature for professional and functional use cases. ### Which printers will be beneficial to this feature? All ### Describe the solution you'd like Please consider implementing local top-surface segmentation. This is a critical feature for professional and functional use cases. ### Describe alternatives you've considered Cura ### Additional context ![Image](https://github.com/user-attachments/assets/169666a5-1e25-415b-b6de-f1f4ec1261c0)

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Reference: github/OrcaSlicer#945