Painted 3MF Export — Blender add-on

Converts a painted 3D model (image texture or vertex colors) into a multicolor .3mf whose colors map to separate filaments / AMS slots in Bambu Studio and OrcaSlicer (e.g. Bambu Lab H2C with AMS).

It reduces the model's colors to a chosen number of filaments (k‑means), assigns each face one of those colors, runs optional print‑prep, and writes a 3MF.

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Install

1. In Blender 4.2+ / 5.x: Edit ▸ Preferences ▸ Get Extensions ▸ ▾ ▸ Install from Disk… and pick painted_3mf_export-1.0.0.zip (or just drag the zip into the Blender window).
2. Enable it if it isn't already.

Builds with no external dependencies (uses Blender's bundled numpy).

Use

1. Select your painted mesh (make it the active object).
2. Open the N‑panel in the 3D Viewport → "Paint→3MF" tab (or use File ▸ Export ▸ Painted Multicolor (.3mf)).
3. Set the number of Filaments (colors) and any print‑prep options.
4. Click Export 3MF and choose a path.
5. Open the .3mf in Bambu Studio / OrcaSlicer → each color appears as its own filament; assign them to your AMS slots and slice.

You can export from Object or Vertex/Texture‑Paint/Sculpt/Edit mode — it switches to Object mode internally and restores your mode afterward. Your scene object is never modified (all work happens on a throwaway copy).

Settings

Setting	Meaning
Color Source	Auto‑detect (image texture → color attribute → flat material), or force one
Filaments (colors)	Target color count (1–16). Fewer are emitted if the model has fewer distinct colors
Quantize In	Perceptual (Lab) (best), Linear, or sRGB clustering space
Seed	k‑means determinism
Validate / Repair Mesh	Weld doubles, remove degenerates, fill holes, recalc normals (watertight)
Scale to Size (mm)	Scale longest dimension to the target mm
Remesh for Color Detail	Voxel‑remesh for crisper color borders (color is sampled before remesh and re‑transferred)
Split Into Parts by Color	Export each color as its own co‑located part instead of one painted mesh (see below)
Write Fallback Materials	Also emit <basematerials> for materials‑aware non‑Bambu slicers

How the colors reach Bambu (important)

Bambu Studio / OrcaSlicer's model loader (bbs_3mf.cpp) ignores the 3MF core <basematerials> block. It only reads the Materials‑extension color group — <m:colorgroup> / <m:color> with per‑triangle pid + p1=p2=p3 — mapping each unique color to its own filament. So this add‑on writes the colors as an m:colorgroup (and keeps <basematerials> only as an inert, non‑Bambu‑relevant extra). It also keeps the Application metadata generic — setting it to BambuStudio-*/OrcaSlicer-* would switch the loader into native project mode and disable this color‑import path.

Split into parts by color

By default the export is one painted mesh — Bambu paints the surface and you remap colors→filaments if needed. With Split Into Parts by Color enabled, the 3MF instead contains one object made of N co-located parts, one per color (a 3MF assembly with a <component> per color at the identity transform).

In the slicer each part shows up separately, so you can assign each part to any filament / AMS slot by hand — handy when your quantized colors don't match the filaments actually loaded in the printer. All parts stay perfectly aligned (same location), so together they reproduce the model.

Each part's open color-seam boundaries are capped into a closed, watertight shell, so the slicer treats it as a real solid — supports go on the outside and nothing renders inside-out. The parts are hollow (sealed outer shell with no solid interior); set wall/infill per part in the slicer as usual. If a part's seam can't be fully sealed it's reported as a warning rather than silently exported broken.

Bambu Studio tip: you may not need this at all. If you import the normal (non-split) export, Bambu Studio 2.5+ shows a "Standard 3mf Import color" dialog that lets you remap each model color to any loaded filament — same goal, no geometry split. Splitting is mainly useful for OrcaSlicer (which ignores per-triangle 3MF colors) or when you want separately re-colorable parts.

Pipeline

work copy → triangulate → sample per‑face sRGB color (image UV / color attr / flat)
→ k‑means quantize to K → bake palette index into a CORNER color attribute
→ [validate/repair] → [scale to mm] → [voxel remesh + BVH color transfer]
→ re‑read labels (snap to palette) → drop degenerate faces
→ write m:colorgroup 3MF (atomic write)

Limitations / notes

• Exports the active object only; other selected meshes are skipped (with a warning).
• Image‑texture path assumes the texture feeds Principled Base Color via the active UV map; sRGB vs. linear is handled per the image's color space/bit depth.
• Voxel remesh produces uniform, blocky color borders — use it only when the source mesh is too low‑poly for clean color edges; it lowers detail otherwise.
• Color count emitted can be less than requested if the model has fewer distinct colors (no phantom filler colors).

Files

__init__.py (register) · props.py (settings) · ui.py (panel/menu) · operator.py (pipeline + operator) · color_sample.py (detect/sample) · quantize.py (k‑means + color spaces) · prep.py (repair/scale/remesh) · threemf.py (3MF writer).