Class LoadSpatially

This strategy ensures that only the data which is in the visible extent of the Map is retrieved from the model. It can only be used on FeatureLayers whose model has a spatial-query capability. See Store.spatialQuery for more information about this capability. If you attempt to use this strategy with a model that does not support spatial queries, an error will be thrown.

Additionally, you can configure a QueryProvider on this loading strategy to further refine the amount of data to load from the FeatureModel.

Note: QueryProvider by defining a WFS query object with the WFSQueryOptions.maxFeatures property. For the given visible extent of the Map this maximum number of features can be loaded. When this happens, the LoadSpatially strategy re-queries when zooming in or out, so that a new set of data is requested for the new view extent.

In a 3D scene it is possible that the visible extent of the Map covers multiple areas with different scales. For example, if the camera is tilted, data on the horizon is visualized at a lower scale than data closer to the camera. To that end, LuciadRIA divides the map in multiple zones that correspond with scale levels that are defined by the QueryProvider. The loading strategy queries the underlying model by passing the bounds and the query object for each visible scale level zone, and combines the data in each zone for a consistent visualization. This approach allows you to visualize large data sets in 3D, while you can still apply data specific business rules when loading and visualizing the data.
Please note that you can suppress this behavior by setting LoadSpatiallyStrategyConstructorOptions.singleQueryLevel to true.

In order to take advantage of this loading capability the QueryProvider should define scale levels and their query objects to limit the number of features for smaller scales, or even to prevent from loading data at all for the least detailed scale (level 0) (QueryProvider.QUERY_NONE). Additionally, you can also define layer's minimum scale or maximum scale at which features should be rendered. LuciadRIA will query the underlying model by passing the bounds computed for the area with scales within layer's scale limits.

  const townQueryFilter = {
    filter: eq(property("class"), literal("town"))
  };

  class CityQueryProvider extends QueryProvider {
    getQueryForLevel(level: number) {
      // no data requested for least detailed level
      if (level === 0) {
        return QueryProvider.QUERY_NONE;
      }
      // data matching the specific filter is only loaded
      if (level === 1) {
        return townQueryFilter;
      }
      // everything is loaded otherwise
      return null;
    }

    // The query provider defines 3 scale levels:
    // The scale level 0 denotes an area with scales smaller than 1 / 50000,
    // The scale level 1 that represents area with scales between than 1 / 50000 and 1 / 1000,
    // The scale level 2 that represents area with scales greater than 1 / 1000 (closer to the observer).
    getQueryLevelScales(layer?: FeatureLayer, map?: Map) {
      return [ 1/50000, 1/1000 ];
    }
  }

  // the cityModel must support spatial queries
  const cityLayer = new FeatureLayer(cityModel, {
    loadingStrategy: new LoadSpatially({queryProvider: new CityQueryProvider()})
  });

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Since

2015.0 load spatially strategy

Since

2018.1 3D multi-scale capability