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Class: DEMData

DEMData is a data structure for decoding, backfilling, and storing elevation data for processing in the hillshade shaders data can be populated either from a pngraw image tile or from serliazed data sent back from a worker. When data is initially loaded from a image tile, we decode the pixel values using the appropriate decoding formula, but we store the elevation data as an Int32 value. we add 65536 (2^16) to eliminate negative values and enable the use of integer overflow when creating the texture used in the hillshadePrepare step.

DEMData also handles the backfilling of data from a tile's neighboring tiles. This is necessary because we use a pixel's 8 surrounding pixel values to compute the slope at that pixel, and we cannot accurately calculate the slope at pixels on a tile's edge without backfilling from neighboring tiles.

Constructors

constructor

new DEMData(uid, data, encoding, redFactor?, greenFactor?, blueFactor?, baseShift?): DEMData

Constructs a DEMData object

Parameters

Name Type Default value Description
uid string | number undefined the tile's unique id
data ImageData | RGBAImage undefined RGBAImage data has uniform 1px padding on all sides: square tile edge size defines stride // and dim is calculated as stride - 2.
encoding DEMEncoding undefined the encoding type of the data
redFactor number 1.0 the red channel factor used to unpack the data, used for custom encoding only
greenFactor number 1.0 the green channel factor used to unpack the data, used for custom encoding only
blueFactor number 1.0 the blue channel factor used to unpack the data, used for custom encoding only
baseShift number 0.0 the base shift used to unpack the data, used for custom encoding only

Returns

DEMData

Defined in

src/data/dem_data.ts:45