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¶
Defined in¶
src/data/dem_data.ts:45
