A shape with scene3d and sp3d but no bevelT was drawn in its flat fill
colour. PowerPoint lights the front face from the light rig whether or
not there is a bevel, so a plain 3-D rotated rectangle is lighter than
its fill. Model the face with the same threePt approximation as the
bevel (no rim), for solid fills.
Wild 3-D slides: s8 6.35 -> 4.26, s9 19.74 -> 17.68. Corpus unchanged
except lo tdf114848 s4 2.13 -> 1.94.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>