Building the 64 tiles of the Banc du Vigilant cost about 1.9 s through per-vertex cell_world_position/normal_at_cell calls, leaving the 3 s load budget with too little headroom (2.1-2.9 s measured, one 4.8 s outlier). TerrainHeightField now returns positions and normals of a cell block in one call, with normal_at_cell sharing the same formula; the tile build drops to about 0.5 s. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>