Walk the PRC product tree into placed, coloured tessellations.
- PrcFile::placements / placements_with(StyleAlpha, EntityOverrides):
every drawable tessellation reached from the model file's roots, placed
by its occurrence path's locations and then the representation item's
local coordinate systems (a 4x4 Matrix) [WD 7.3.10.1, 7.6.3.2].
- Colours: styles and materials from the file structure globals, the
father/son inheritance bits [WD 7.2.4.2], style transparency combined
with material alpha by StyleAlpha, per-face styles and topology
references via Placement::triangle_colours. A prototype's part is
coloured by its own structure's styles. A colour index counts the colour
array's doubles (pdf-issues #816).
- Occurrences' entity references: colour, hide or relocate the entity
they name, in the occurrence's subtree, everywhere, or not at all.
- PrcFile::model_tree: the assembly tree as a model-tree panel lists it,
with name sources, visibility and each node's placement range.
- TriangleMesh::transformed applies a Matrix: positions, cofactor-mapped
normals, winding flipped under a mirror.
Never panics: occurrence and prototype cycles are Malformed; depth 64,
2^20 visits, MAX_PLACEMENTS and a face-override ceiling bound the walk;
counts are checked against the remaining data before allocating.
Markups, views, scene lights and clipping planes are Unsupported;
textures are read past.
Field orders the working draft leaves open follow prc-rs (MIT); each is
marked `// prc-rs:`, as are the step-1 container, Double and schema
choices that did.
Adapted from pdfcer (MIT, same author), crates/pdfcer-3d/src/tree and
vec3.rs at 0c9742b5936232af89cd707138ef149dc1f4a660.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SqmHYx8FiWM5PcsoiErgp9
