WorldPicker.Pick previously had no occlusion test — any entity along
the click ray within maxDistance was a candidate, including ones
behind walls. Adds the CellBspRayOccluder static helper that
Möller-Trumbore-tests the click ray against every polygon in every
currently-cached EnvCell BSP, returning the nearest wall-hit `t`.
Both Pick overloads gate candidate selection by that wall-t (legacy
ray-sphere via world-space `t`, screen-rect via camera-space clip.W
depth — matching ScreenProjection.TryProjectSphereToScreenRect's
convention).
PhysicsDataCache exposes a new CellStructIds snapshot accessor so the
caller can iterate without needing the private cache dictionary.
CellPhysics.BSP/PhysicsPolygons/Vertices relaxed from required to
nullable so test fixtures can construct a CellPhysics from Resolved
alone without a real DAT BSP object. GameWindow snapshots the loaded
cell physics on each Pick call and passes the occluder callback.
Closes#86.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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