raycastAt method
Attempts to pick a model at normalized device coordinates ndc
(x/y in [-1, 1], y up), used by tap picking (jsr.scene3d.onTap).
Returns {modelId, point: [x, y, z]} for the nearest hit, or null on a
miss or when the host does not support raycasting.
Implementation
Map<String, dynamic>? raycastAt(Offset ndc) => null;