Building Blocks

The API re-exports common modules for custom workflows. These are the same modules used internally by the import/export pipeline.

from io_mesh_3mf.api import colors, types, segmentation, units

Colors

io_mesh_3mf.common.colors — hex/RGB conversion and sRGB/linear transforms.

Function	Signature	Description
`srgb_to_linear`	`(c: float) -> float`	Convert a single sRGB gamma component to linear.
`linear_to_srgb`	`(c: float) -> float`	Convert a single linear component to sRGB gamma.
`hex_to_rgb`	`(hex_str: str) -> Tuple[float, float, float]`	Convert `#RRGGBB` hex string to an `(r, g, b)` tuple of 0-1 floats.
`hex_to_linear_rgb`	`(hex_str: str) -> Tuple[float, float, float]`	Convert `#RRGGBB` hex string to an `(r, g, b)` tuple in linear space.
`rgb_to_hex`	`(r: float, g: float, b: float) -> str`	Convert 0-1 float RGB values to a `#RRGGBB` hex string.
`linear_rgb_to_hex`	`(r: float, g: float, b: float) -> str`	Convert linear RGB (0-1) to a `#RRGGBB` sRGB hex string.

Units

io_mesh_3mf.common.units — unit conversion between 3MF and Blender.

Variable	Description
`threemf_to_metre`	Dict mapping 3MF unit strings to metre scale factors
`blender_to_metre`	Dict mapping Blender unit strings to metre scale factors

Function	Signature	Description
`import_unit_scale`	`(context: bpy.types.Context, root, global_scale: float) -> float`	Compute the import scale factor from 3MF document units to Blender scene units.
`export_unit_scale`	`(context: bpy.types.Context, global_scale: float) -> float`	Compute the export scale factor from Blender scene units to 3MF millimeters.

Types (Dataclasses)

io_mesh_3mf.common.types — internal data structures used throughout the pipeline.

Key dataclasses:

ResourceObject — A parsed <object> element from a 3MF model file.
Component — A <component> reference inside an <object>.
ResourceMaterial — Material properties parsed from 3MF basematerials, colorgroups, or PBR extensions.
ResourceTexture — A <texture2d> element — texture image metadata.
ResourceTextureGroup — A <texture2dgroup> container for texture coordinates.
ResourceComposite — Composite materials (Materials Extension) for round-trip support.
ResourceMultiproperties — Multiproperties (Materials Extension) for round-trip support.
ResourcePBRTextureDisplay — Textured PBR display properties (metallic/specular texture maps).
ResourceColorgroup — Passthrough storage for <colorgroup> elements.
ResourcePBRDisplayProps — Passthrough storage for non-textured PBR display properties.

Segmentation Codec

io_mesh_3mf.common.segmentation — encode/decode hex segmentation strings used for multi-material paint data.

Class	Description
`SegmentationNode`	A node in the triangle subdivision tree.
`SegmentationDecoder`	Decodes PrusaSlicer segmentation strings into subdivision trees.
`TriangleSubdivider`	Subdivides triangles based on segmentation trees.
`SegmentationEncoder`	Encodes subdivision trees back to PrusaSlicer hex strings.

The codec implements the recursive 4-bit nibble encoding used by Orca Slicer and PrusaSlicer, where each nibble xxyy encodes the state (2 bits) and split direction (2 bits) of a triangle subdivision.

Extensions

io_mesh_3mf.common.extensions — extension registry and validation.

Class	Description
`Extension`	Represents a 3MF extension with its metadata and capabilities.
`ExtensionManager`	Manages active extensions for import/export operations.

Metadata

io_mesh_3mf.common.metadata — metadata storage and merging.