Approximate retained byte footprint, for the cache budget.
True when this tile is entirely water (the whole-tile flag, set). Lets the mesh builder emit a single quad instead of probing the grid per cell.
True when this tile is entirely land (no water anywhere) — skip building any water geometry for it.
True when (lon, lat) in radians falls within this tile's rectangle.
Water at a u/v fraction in [0,1] (u west→east, v south→north).
Water at (lon, lat) in radians, or null when the point is outside the tile.
Land/water lookup for one tile, from the quantized-mesh
watermaskextension. A whole-tile flag (size === 1) answers the same for the entire rectangle; a 256×256 grid (size === 256) is sampled at the query's u/v fraction. Rows run south→north, columns west→east (matching the tile's u/v), and a byte ≥ 128 counts as water (the coastline ramp straddles 128). Retained on TerrainContent so TerrainTileset.waterAt can answer per point.