Reads a 3MF package into the crate's Scene: mesh objects, component
objects and build items with their transforms (as a node hierarchy; an
object placed several times is one mesh), the unit, base materials,
colour groups, texture coordinate groups and their textures.
The package is opened with craft-opc (3MF is an OPC package) and the model
part is read with craft-xml's pull reader, so a large part never becomes a
tree. read_model_part reads a model part on its own.
Ported from storytold/deckcraft#743 (crates/mesh/src/threemf.rs). What
that reader did for DeckCraft and stays there: baking placements into
world-space triangles, the turn to Y-up, scaling to metres, and decoding
the textures. Here placements stay nodes, positions stay in the file's
unit and axes (Model::unit says which), and a texture is its bytes.
Co-authored-by: uvxszi <uvxszi@gmail.com>
Dylan M. Tayloranduvxszi
9e9c044fab