OptionalonOptional consumer callback fired once per successful tile load.
EPSG:3857 origin subtracted from all mesh positions, because absolute coordinates (~6·10⁶ m)
exceed float32 precision (~0.5 m), making landmark edges tremble while zooming. null
until the first tile with meshes loads.
Source of tiled glTF/GLB models for a ModelsLayer.
Tracks the tiles covering the current viewport, fetches each tile's models once and keeps them in a Three.js Group that the owning layer renders.