Someone Reverse-Engineered Bambu's Per-Face Color Format. The Fix Is a Free Browser Tool.

If you’ve ever exported a multi-color 3MF from Bambu Studio and watched the per-face paint assignments disappear when another slicer opens it, this solves that problem.

What Was Broken

Bambu Studio stores per-face color assignments using a proprietary extension to the 3MF format — the paint_color field. This metadata is not part of the Standard 3MF Materials and Properties Extension that OrcaSlicer, PrusaSlicer, and other tools read. When you export a painted model from Bambu Studio and try to open it anywhere else, the color assignments either disappear or cause errors.

This has been a friction point for multi-color 3MF workflows: the community has converged on Bambu hardware and AMS for multi-material printing, but the tooling ecosystem that exists around 3MF (remixing models, sharing on Printables, passing files between slicers) doesn’t preserve the paint work.

What Was Built

A community developer on r/BambuLab has reverse-engineered the paint_color format and published a free browser tool that reads Bambu Studio’s per-face color data and writes it as a Standard 3MF Materials and Properties Extension — the format that Bambu Studio, OrcaSlicer, and PrusaSlicer all read natively.

The tool runs in the browser with no install required, preserves all per-face assignments, and produces an output 3MF that round-trips correctly into any of the major slicers. The conversion is bidirectional: existing Standard 3MF files with color data also import correctly.

For multi-color workflows, this matters in practice: you can now share a painted 3MF with another maker running OrcaSlicer and have the colors survive the exchange. Remixed models that derive from painted originals preserve the intent of the color assignments.

The Broader Context

Bambu’s extension approach is not malicious — it was faster to implement feature-specific metadata this way during rapid development. But as the community has grown and cross-slicer workflows have become common, the proprietary format creates real friction for power users.

The Standard 3MF Consortium’s Materials and Properties Extension provides an interoperable path for exactly this use case. Browser tools like Layerpaint (which adds per-face colors to models for multi-material printing) use the standard extension by default. The community solution here is bringing Bambu’s format into alignment with what the broader ecosystem already supports.

Source: r/BambuLab

Content created with AI assistance and reviewed for accuracy.