tiles: make the internal tile extent of vector tiles configurable - #595
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cportele wants to merge 2 commits into
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tiles: make the internal tile extent of vector tiles configurable#595cportele wants to merge 2 commits into
cportele wants to merge 2 commits into
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The internal coordinate system of a vector tile was fixed to the tile extent of the tiling scheme, 4096 for WebMercatorQuad. A tileset can now declare its own tile extent, which increases the geometric precision of its tiles and reduces the simplification of their geometries, at the cost of larger tiles. That makes it possible to serve fewer zoom levels and let clients overzoom the last one. The extent of a tileset applies to the encoder, the precision model, the Douglas-Peucker distance, the buffer around a tile and the optimized PostGIS tile generation. A combined tileset encodes with its own extent; a source tileset that uses a different one is rescaled.
The defaults of a tile provider are not merged into its tilesets when the provider is loaded, every use of a tileset has to merge them, and combining did not. A combined tileset that took its tile extent from the tileset defaults was therefore encoded with the tile extent of the tiling scheme, which quantised the coordinates of its source tilesets back down to that extent.
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Closes ldproxy/ldproxy#1723
The extent of a tileset applies to the encoder, the precision model, the Douglas-Peucker distance, the buffer around a tile and the optimized PostGIS tile generation. A combined tileset encodes with its own extent; a source tileset that uses a different one is rescaled.