Add `GlbScene` — the viewer that renders a baked GLB artifact with no
parametric scene graph, and finish the phase-1 export contract it consumes.
Viewer (packages/viewer):
- GlbScene: loads the artifact, drives a building → level → zone → node drill
hierarchy on useViewer.selection. Room/zone picking resolves from the floor
plane (ray ∩ floor + point-in-polygon), node picking uses a footprint test,
so walls/ceilings/zone-helpers never skew or block selection. Level modes
(stacked/exploded/solo), dollhouse (hide a focused floor's ceilings + roof so
rooms are visible and pickable), reconstructed zone floor fills + gradient
edge borders + room labels (faded, hover-brightened), baked door/window
open clips, click-outside / empty-space deselect, and the shared outline
post-FX. Exported as GlbScene/GlbLevel/GlbIdentity/GlbHover.
- post-processing: composite the zone-pass tint into the base scene so rooms
show whether or not SSGI is enabled (previously only added in the SSGI branch).
Export contract (packages/editor/src/lib/glb-export.ts):
- Convert WebGPU NodeMaterials to classic glTF-standard materials; decompress
KTX2 maps via WebGPUTextureUtils so GLTFExporter can embed them.
- Stamp name + extras identity (pascalId/kind/label/openable/clips), bake
door/window open clips (loop:false), strip editor overlays (off-layer +
invisible-material hitboxes) so cutouts aren't plugged.
- Fix opaque-but-flagged-transparent materials (no spurious alphaMode=BLEND)
and BackSide → FrontSide + winding flip (glTF has no back-face-only).
- Force levels + zones visible and stamp level display names + zone polygons so
every floor bakes and /viewer can reconstruct rooms and label the breadcrumb.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
