GridLayer

The GridLayer renders a grid heatmap based on an array of inputs. It takes the constant cell size and aggregates input objects into cells. The color and height of a cell are determined based on the objects it contains.

This layer renders either a GPUGridLayer or a CPUGridLayer, depending on its props and whether GPU aggregation is supported. For more details check the GPU Aggregation section below.

GridLayer is a CompositeLayer.

import DeckGL from '@deck.gl/react';
import {GridLayer} from '@deck.gl/aggregation-layers';

function App({data, viewState}) {
  /**
   * Data format:
   * [
   *   {COORDINATES: [-122.42177834, 37.78346622]},
   *   ...
   * ]
   */
  const layer = new GridLayer({
    id: 'new-grid-layer',
    data,
    pickable: true,
    extruded: true,
    cellSize: 200,
    elevationScale: 4,
    getPosition: d => d.COORDINATES
  });

  return <DeckGL viewState={viewState}
    layers={[layer]}
    getTooltip={({object}) => object && `${object.position.join(', ')}\nCount: ${object.count}`} />;
}

Note: The GridLayer at the moment only works with COORDINATE_SYSTEM.LNGLAT.

Installation

To install the dependencies from NPM:

npm install deck.gl
# or
npm install @deck.gl/core @deck.gl/layers @deck.gl/aggregation-layers

import {GridLayer} from '@deck.gl/aggregation-layers';
new GridLayer({});

To use pre-bundled scripts:

<script src="https://unpkg.com/deck.gl@^8.0.0/dist.min.js"></script>
<!-- or -->
<script src="https://unpkg.com/@deck.gl/core@^8.0.0/dist.min.js"></script>
<script src="https://unpkg.com/@deck.gl/layers@^8.0.0/dist.min.js"></script>
<script src="https://unpkg.com/@deck.gl/aggregation-layers@^8.0.0/dist.min.js"></script>

new deck.GridLayer({});

Properties

Inherits from all Base Layer and CompositeLayer properties.

Render Options

cellSize (Number, optional)

• Default: 1000

Size of each cell in meters

colorDomain (Array, optional)

• Default: [min(colorWeight), max(colorWeight)]

Color scale domain, default is set to the extent of aggregated weights in each cell. You can control how the colors of cells are mapped to weights by passing in an arbitrary color domain. This is useful when you want to render different data input with the same color mapping for comparison.

colorRange (Array, optional)

• Default: colorbrewer 6-class YlOrRd

Specified as an array of colors [color1, color2, ...]. Each color is an array of 3 or 4 values [R, G, B] or [R, G, B, A], representing intensities of Red, Green, Blue and Alpha channels. Each intensity is a value between 0 and 255. When Alpha not provided a value of 255 is used.

colorDomain is divided into colorRange.length equal segments, each mapped to one color in colorRange.

coverage (Number, optional)

• Default: 1

Cell size multiplier, clamped between 0 - 1. The displayed size of cell is calculated by coverage * cellSize. Note: coverage does not affect how objects are binned.

elevationDomain (Array, optional)

• Default: [0, max(elevationWeight)]

Elevation scale input domain, default is set to between 0 and the max of aggregated weights in each cell. You can control how the elevations of cells are mapped to weights by passing in an arbitrary elevation domain. This is useful when you want to render different data input with the same elevation scale for comparison.

elevationRange (Array, optional)

• Default: [0, 1000]

Elevation scale output range

elevationScale (Number, optional)

• Default: 1

Cell elevation multiplier. This is a handy property to scale all cells without updating the data.

extruded (Boolean, optional)

• Default: true

Whether to enable cell elevation.If set to false, all cell will be flat.

upperPercentile (Number, optional)

• Default: 100

Filter cells and re-calculate color by upperPercentile. Cells with value larger than the upperPercentile will be hidden.

lowerPercentile (Number, optional)

• Default: 0

Filter cells and re-calculate color by lowerPercentile. Cells with value smaller than the lowerPercentile will be hidden.

elevationUpperPercentile (Number, optional)

• Default: 100

Filter cells and re-calculate elevation by elevationUpperPercentile. Cells with elevation value larger than the elevationUpperPercentile will be hidden.

elevationLowerPercentile (Number, optional)

• Default: 100

Filter cells and re-calculate elevation by elevationLowerPercentile. Cells with elevation value smaller than the elevationLowerPercentile will be hidden.

colorScaleType (String, optional)

• Default: 'quantize'

Scaling function used to determine the color of the grid cell, default value is 'quantize'. Supported Values are 'quantize', 'linear', 'quantile' and 'ordinal'.

fp64 (Boolean, optional)

• Default: false

Whether the aggregation should be performed in high-precision 64-bit mode. Note that since deck.gl v6.1, the default 32-bit projection uses a hybrid mode that matches 64-bit precision with significantly better performance.

gpuAggregation (bool, optional)

• Default: false

When set to true, aggregation is performed on GPU, provided other conditions are met, for more details check the GPU Aggregation section below. GPU aggregation can be a lot faster than CPU depending upon the number of objects and number of cells.

Note: GPU Aggregation is faster only when using large data sets. For smaller data sets GPU Aggregation could be potentially slower than CPU Aggregation.

material (Object, optional)

• Default: true

This is an object that contains material props for lighting effect applied on extruded polygons. Check the lighting guide for configurable settings.

colorAggregation (String, optional)

• Default: 'SUM'

Defines the operation used to aggregate all data object weights to calculate a cell's color value. Valid values are 'SUM', 'MEAN', 'MIN' and 'MAX'. 'SUM' is used when an invalid value is provided.

getColorWeight and colorAggregation together determine the elevation value of each cell. If the getColorValue prop is supplied, they will be ignored. Note that supplying getColorValue disables GPU aggregation.

Example 1 : Using count of data elements that fall into a cell to encode the its color

• Using getColorValue

...
const layer = new CPUGridLayer({
  id: 'my-grid-layer',
  ...
  getColorValue: points => points.length,
  ...
});

• Using getColorWeight and colorAggregation

...
const layer = new CPUGridLayer({
  id: 'my-grid-layer',
  ...
  getColorWeight: point => 1,
  colorAggregation: 'SUM'
  ...
});

Example 2 : Using mean value of 'SPACES' field of data elements to encode the color of the cell

• Using getColorValue

function getMean(points) {
  return points.reduce((sum, p) => sum += p.SPACES, 0) / points.length;
}
...
const layer = new CPUGridLayer({
  id: 'my-grid-layer',
  ...
  getColorValue: getMean,
  ...
});

• Using getColorWeight and colorAggregation

...
const layer = new CPUGridLayer({
  id: 'my-grid-layer',
  ...
  getColorWeight: point => point.SPACES,
  colorAggregation: 'SUM'
  ...
});

If your use case requires aggregating using an operation that is not one of 'SUM', 'MEAN', 'MAX' and 'MIN', getColorValue should be used to define such custom aggregation function. In those cases GPU aggregation is not supported.

elevationAggregation (String, optional)

• Default: 'SUM'

Defines the operation used to aggregate all data object weights to calculate a cell's elevation value. Valid values are 'SUM', 'MEAN', 'MIN' and 'MAX'. 'SUM' is used when an invalid value is provided.

getElevationWeight and elevationAggregation together determine the elevation value of each cell. If the getElevationValue prop is supplied, they will be ignored. Note that supplying getElevationValue disables GPU aggregation.

Example 1 : Using count of data elements that fall into a cell to encode the its elevation

• Using getElevationValue

...
const layer = new CPUGridLayer({
  id: 'my-grid-layer',
  ...
  getElevationValue: points => points.length
  ...
});

• Using getElevationWeight and elevationAggregation

...
const layer = new CPUGridLayer({
  id: 'my-grid-layer',
  ...
  getElevationWeight: point => 1,
  elevationAggregation: 'SUM'
  ...
});

Example 2 : Using maximum value of 'SPACES' field of data elements to encode the elevation of the cell

• Using getElevationValue

function getMax(points) {
  return points.reduce((max, p) => p.SPACES > max ? p.SPACES : max, -Infinity);
}
...
const layer = new CPUGridLayer({
  id: 'my-grid-layer',
  ...
  getElevationValue: getMax,
  ...
});

• Using getElevationWeight and elevationAggregation

...
const layer = new CPUGridLayer({
  id: 'my-grid-layer',
  ...
  getElevationWeight: point => point.SPACES,
  elevationAggregation: 'MAX'
  ...
});

If your use case requires aggregating using an operation that is not one of 'SUM', 'MEAN', 'MAX' and 'MIN', getElevationValue should be used to define such custom aggregation function. In those cases GPU aggregation is not supported.

getElevationValue (Function, optional)

• Default: null

After data objects are aggregated into cells, this accessor is called on each cell to get the value that its elevation is based on. If supplied, this will override the effect of getElevationWeight and elevationAggregation props. Note that supplying this prop disables GPU aggregation.

Arguments:

• objects (Array) - a list of objects whose positions fall inside this cell.
• objectInfo (Object) - contains the following fields:
  • indices (Array) - the indices of objects in the original data
  • data - the value of the data prop.

Data Accessors

getPosition (Function, optional)

• Default: object => object.position

Method called to retrieve the position of each object.

getColorWeight (Function, optional)

• Default: 1

The weight of a data object used to calculate the color value for a cell.

• If a number is provided, it is used as the weight for all objects.
• If a function is provided, it is called on each object to retrieve its weight.

getColorValue (Function, optional)

• Default: null

After data objects are aggregated into cells, this accessor is called on each cell to get the value that its color is based on. If supplied, this will override the effect of getColorWeight and colorAggregation props. Note that supplying this prop disables GPU aggregation.

Arguments:

• objects (Array) - a list of objects whose positions fall inside this cell.
• objectInfo (Object) - contains the following fields:
  • indices (Array) - the indices of objects in the original data
  • data - the value of the data prop.

getElevationWeight (Function, optional)

• Default: 1

The weight of a data object used to calculate the elevation value for a cell.

• If a number is provided, it is used as the weight for all objects.
• If a function is provided, it is called on each object to retrieve its weight.

Callbacks

onSetColorDomain (Function, optional)

• Default: ([min, max]) => {}

This callback will be called when cell color domain has been calculated.

onSetElevationDomain (Function, optional)

• Default: ([min, max]) => {}

This callback will be called when cell elevation domain has been calculated.

GPU Aggregation

Performance Metrics

The following table compares the performance between CPU and GPU aggregations using random data:

Numbers are collected on a 2016 15-inch Macbook Pro (CPU: 2.8 GHz Intel Core i7 and GPU: AMD Radeon R9 M370X 2 GB)

Fallback Cases

This layer performs aggregation on GPU when the browser is using WebGL2 and the gpuAggregation prop is set to true, but will fallback to CPU in the following cases:

Percentile Props

When following percentile props are set, it requires sorting of aggregated values, which cannot be supported when aggregating on GPU.

• lowerPercentile, upperPercentile, elevationLowerPercentile and elevationUpperPercentile.

Color and Elevation Props

When colorScaleType props is set to a 'quantile' or 'ordinal', aggregation will fallback to CPU. For GPU Aggregation, use 'quantize', 'linear'.

Color Scale Type Props

When following percentile props are set, it requires sorting of aggregated values, which cannot be supported when aggregating on GPU.

• lowerPercentile, upperPercentile, elevationLowerPercentile and elevationUpperPercentile.

Domain setting callbacks

When using GPU Aggregation, onSetColorDomain and onSetElevationDomain are not fired.

Sub Layers

The GridLayer renders the following sublayers:

• CPU - a CPUGridLayer when using CPU aggregation.

• GPU - a GPUGridLayer when using GPU aggregation.

Source

modules/aggregation-layers/src/grid-layer