Pure function translating Setup -> IReadOnlyList<ShadowShape>. Walks
CylSpheres + Spheres (only when no CylSpheres) + Parts (only when the
GfxObj has a non-null PhysicsBSP), using PlacementFrames in the same
Resting -> Default -> first-available priority as SetupMesh.Flatten.
Six tests pin the behavior: door setup produces 4 shapes (0+1+3), sphere
local offset matches Setup data, parts without BSP are skipped, creature
setups with CylSpheres skip Spheres, scale factor multiplies all radii
and offsets, empty setup returns empty list, null setup throws.
No callers in this commit; RegisterMultiPart + the GameWindow callers
follow.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
