- Bodies carry a Paint for export (opacity, per-face colours), set by
Document::painted from the appearance model. The paint comes from a
face appearance, a body/component appearance's opacity or a material
look (Glass), and falls back to the paint the body was imported with.
- STEP: faces with colours of their own get a STYLED_ITEM on their
ADVANCED_FACE. See-through looks add SURFACE_STYLE_TRANSPARENT.
Differently coloured pieces are not merged into one face.
- STEP import reads face styles and transparency. The reader tracks the
file face of each kernel face (bands split in two keep it), so imported
face colours land on the right faces; the design shows them through
face_colors.
- 3MF: per-triangle colours (pid/p1 into the base materials, carried
through welding) and the object's alpha (#RRGGBBAA).
- Tests: a blue half-transparent cube with a red top exports, re-imports
with its opacity and the red top face, and keeps it when opened and
exported again. 3MF writes the alpha and the face entry.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL
