Builds a synthetic child QuantizedMeshTile for child quadrant (dx, dy)
of a parent surface, by clipping the parent triangles to that quadrant. dx is
0 (west) or 1 (east); dy is 0 (north) or 1 (south) — matching the engine's
north-down tile-y convention, where v=0 is the south edge so the north child
(dy=0) takes the parent's upper-v half.
The returned tile's header carries only the (re-derived) child height range and
zeroed bounding/center fields — the terrain builder reads just min/max height,
and the tileset supplies the child's bounds from its rectangle. No water mask or
normals are produced (the builder computes geodetic normals; water doesn't
upsample).
Builds a synthetic child QuantizedMeshTile for child quadrant
(dx, dy)of a parent surface, by clipping the parent triangles to that quadrant.dxis 0 (west) or 1 (east);dyis 0 (north) or 1 (south) — matching the engine's north-down tile-y convention, where v=0 is the south edge so the north child (dy=0) takes the parent's upper-v half.The returned tile's header carries only the (re-derived) child height range and zeroed bounding/center fields — the terrain builder reads just min/max height, and the tileset supplies the child's bounds from its rectangle. No water mask or normals are produced (the builder computes geodetic normals; water doesn't upsample).