mvt-layer.md

import {MVTLayerDemo} from 'website-components/doc-demos/geo-layers';

MVTLayer

MVTLayer is a derived TileLayer that makes it possible to visualize very large datasets through MVTs (Mapbox Vector Tiles). Behaving like TileLayer, it will only load, decode and render MVTs containing features that are visible within the current viewport.

Data is loaded from URL templates in the data property.

This layer also handles feature clipping so that there are no features divided by tile divisions.

import DeckGL from '@deck.gl/react';
import {MVTLayer} from '@deck.gl/geo-layers';

function App({viewState}) {
  const layer = new MVTLayer({
    data: `https://a.tiles.mapbox.com/v4/mapbox.mapbox-streets-v7/{z}/{x}/{y}.vector.pbf?access_token=${MAPBOX_TOKEN}`,

    minZoom: 0,
    maxZoom: 23,
    getLineColor: [192, 192, 192],
    getFillColor: [140, 170, 180],

    getLineWidth: f => {
      switch (f.properties.class) {
        case 'street':
          return 6;
        case 'motorway':
          return 10;
        default:
          return 1;
      }
    },
    lineWidthMinPixels: 1
  });

  return <DeckGL viewState={viewState} layers={[layer]} />;
}

Installation

To install the dependencies from NPM:

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

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

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/geo-layers@^8.0.0/dist.min.js"></script>

new deck.MVTLayer({});

Properties

Inherits all properties from TileLayer and base Layer, with exceptions indicated below.

If using the default renderSubLayers, supports all GeoJSONLayer properties to style features.

data (String | Array | JSON)

Required. It defines the remote data for the MVT layer.

• String: Either a URL template or a TileJSON URL.

• Array: an array of URL templates. It allows to balance the requests across different tile endpoints. For example, if you define an array with 4 urls and 16 tiles need to be loaded, each endpoint is responsible to server 16/4 tiles.

• JSON: A valid TileJSON object.

See TileLayer's data prop documentation for the URL template syntax.

The getTileData prop from the TileLayer class will not be called.

uniqueIdProperty (String)

Optional. Needed for highlighting a feature split across two or more tiles if no feature id is provided.

An string pointing to a tile attribute containing a unique identifier for features across tiles.

highlightedFeatureId (Number | String)

• Default: null

Optional. When provided, a feature with ID corresponding to the supplied value will be highlighted with highlightColor.

If uniqueIdProperty is provided, value within that feature property will be used for ID comparison. If not, feature id will be used.

loadOptions (Object, optional)

On top of the default options, also accepts options for the following loaders:

• MVTLoader

Note that by default, the MVTLoader parses data using web workers, with code loaded from a CDN. To change this behavior, see loaders and workers.

binary (Boolean, optional)

• Default: false

Use tile data in binary format to improve performance (2-3x faster on large datasets). It removes the need for serialization and deserialization of data transferred by the worker back to the main process.

Remarks:

• It requires using GeoJsonLayer in the renderSubLayers callback.

Callbacks

onDataLoad (Function, optional)

Called if data is a TileJSON URL when it is successfully fetched

Receives arguments:

• tileJSON (Object) - the loaded TileJSON

Methods

getRenderedFeatures (Function)

Get the rendered features in the current viewport.

If a uniqueIdProperty is provided only unique properties are returned.

Requires pickable prop to be true.

Parameters:

• maxFeatures (Number, optional): Max number of features to retrieve when getRenderedFeatures is called. Default to null.

Returns:

• An array with geometries in GeoJSON format.

Remarks:

• As it's an expensive operation, it's not recommended to call getRenderedFeatures every time onViewStateChange is executed, use a debounce function instead.
• In most of the cases you probably want to use it attached to onViewStateChange and onViewportLoad.

Tile

Aside from all members of the Tile class, tile instances from the MVTLayer also include the following fields:

dataInWGS84 (Array)

A list of features in world coordinates (WGS84).

Usage example:

const onViewportLoad = tiles => {
  tiles.forEach(tile => {
    // data in world coordinates (WGS84)
    const dataInWGS84 = tile.dataInWGS84;
  });
};
new MVTLayer({
  id: "..."
  data: "..."
  onViewportLoad
})

Source

modules/geo-layers/src/mvt-layer/mvt-layer.js