MSFContourTileDataSource

Constructs a ContourTileDataSource object.

Constructs a ContourTileDataSource object, inferring the elevation decoder from the data source ‘encoding’ metadata (defaults to terrarium).

Returns the name of the generated vector tile layer.

Sets the name of the generated vector tile layer. This must match the layer id used in the CartoCSS style.

Returns the base contour interval in meters.

Sets the base contour interval in meters. This is the FINEST interval generated; coarser tile zooms generate a multiple of it, see setIntervalMultiplier.

Sets the interval multiplier used at tile zooms up to (and including) maxZoom. A tile carries every elevation that is a multiple of BaseInterval x multiplier, and each contour carries ‘div’ so the style picks per camera zoom which of them to draw.

The default table is (9, 50), (11, 10), (13, 5), (any, 1): 500m, 100m, 50m, 10m for a 10m base.

TWO RULES when changing it:

• the multipliers must NEST - each one a multiple of the finer ones - or a line stops dead at the border between tiles of different zoom (200 and 500 share no elevation);
• cost tracks the number of contours emitted, so a multiplier twice as fine is about twice the tracing, the geometry and the draw. Make it no finer than what the style actually draws at the camera zoom where tiles of that zoom are used.

Returns the interval multiplier that applies at the given tile zoom.

Removes every interval multiplier entry, so BaseInterval is used at every zoom.

Returns the target grid resolution used for contour tracing.

Sets the target grid resolution used for contour tracing. The DEM is subsampled so that the traced grid is at most this many samples per side. Lower values produce coarser but much cheaper geometry (fewer vertices to trace, simplify, upload and drape over terrain). Over 3D TERRAIN use 0 (the DEM’s own resolution): the surface is displaced by every texel of the same tile, so a line traced on a subsampled grid follows a height field the ground does not have and cuts through everything between its samples.

Sets the tracing grid resolution used at tile zooms up to (and including) maxZoom, overriding Resolution there. Tracing cost is roughly quadratic in this, and a low zoom tile covers so much ground that a fine grid buys nothing, so this is the cheapest knob to turn for zoomed-out frames - but a costly one for QUALITY: a tile is drawn at roughly the same screen size whatever its zoom, so a grid that shrinks with zoom puts contour vertices hundreds of metres apart and the lines read as straight chords. Empty by default for that reason: Resolution applies at every zoom, and low zoom saves through the interval instead.

Returns the tracing grid resolution that applies at the given tile zoom.

Removes every per-zoom resolution entry, so Resolution is used at every zoom.

Returns the minimum zoom at which contour geometry is generated.

Sets the minimum zoom at which contour geometry is generated. Below this zoom loadTile returns an empty (but valid) tile without fetching or tracing the DEM. Note: in CartoCSS ‘zoom’ means the TILE zoom, so the style must also draw the desired zoom range for contours to actually appear.

Returns whether seamless tile edges are enabled.

Sets whether to generate seamless tile edges. When enabled, the east/north/north-east neighbour DEM tiles are fetched so that a tile’s east and north edges use the exact same elevation samples as the adjacent tiles, removing the small gaps where contour lines meet at tile boundaries. This costs up to three extra DEM tile fetches/decodes per tile (they are usually cached).

Returns the terrain options whose elevation manager the label stubs read.

Sets the terrain options whose ELEVATION MANAGER the label stubs are generated from. With it, a stub tile costs no tile of its own: the seeds are walked over the elevation grid the 3D terrain has already fetched and decoded for that tile, which is how tangram generates contour labels (core/src/style/contourTextStyle.cpp reads the tile’s own elevation raster). Without it, the source loads and decodes the DEM tile a second time - measured at 44% of a tile decode thread, half of it in the image decode alone.

The terrain options must be driven by the SAME elevation data source this tile source wraps, or the labels state heights the map does not show. Only the stubs use it; traced contour geometry keeps reading the DEM at its own resolution, which the terrain’s mesh-capped elevation level cannot supply.

Returns whether only short label stubs are generated instead of full contour lines.

Sets whether to generate short label stubs instead of full contour lines. A stub is a ~20 point polyline lying ON a contour, long enough to lay the elevation text along and nothing more: a grid of 4x4 seeds per tile is walked down the elevation gradient onto the nearest contour level and then along it. The tile then carries a handful of tiny features instead of the full traced geometry, which is what makes the labels affordable when the contour LINES are drawn by the terrain shader (HillshadeRasterTileLayer.setContourEnabled) rather than from this geometry.

The features keep the same layer name and the same ‘ele’/‘div’ attributes, so the existing text rules style them unchanged; they additionally carry ‘stub’ = 1, so a style that also draws contour LINES from this layer can exclude them with a [stub=0] filter.

The stub levels must match the levels the shader draws, or the labels sit between the lines: set LabelInterval to the layer’s ContourInterval (or leave both at their zoom defaults).

Returns the contour interval used for label stubs.

Sets the contour interval used for label stubs, in meters. Use 0 to follow the same zoom-dependent interval the traced geometry uses.

Returns the simplification tolerance in tile pixels.

Sets the simplification tolerance in tile pixels. Use 0.0 to disable simplification.

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