LineOfSightViewModel

AMD: require(["esri/widgets/LineOfSight/LineOfSightViewModel"], (LineOfSightViewModel) => { /* code goes here */ });
ESM: import LineOfSightViewModel from "@arcgis/core/widgets/LineOfSight/LineOfSightViewModel";
Class: esri/widgets/LineOfSight/LineOfSightViewModel
Inheritance: LineOfSightViewModel Accessor
Since: ArcGIS Maps SDK for JavaScript 4.14

Provides the logic for the LineOfSight widget. Use it to create your own widget or to get access to the observer, targets and intersections.

Using the LineOfSightViewModel you can programmatically set the observer and targets for a line of sight analysis.

// instantiate a new view model
const losViewModel = new LineOfSightViewModel({
 view: view
});

// set an observer
losViewModel.observer = new Point({
  latitude: 42.3521,
  longitude: -71.0559,
  z: 147.139
});

// set a target by passing in a LineOfSightTarget to the targets collection
losViewModel.targets = [new LineOfSightTarget({
   location: new Point({
     latitude: 42.352,
     longitude: -71.051,
     z: 0
   })
})];

// when using JavaScript LineOfSightTarget can be autocast
losViewModel.targets = [{
   location: {
     latitude: 42.352,
     longitude: -71.051,
     z: 0
   }
}];

The view model can also be used to control the different states of the analysis: start() enters the creation state where the user can add the observer and targets. stop() enters the created state where the user can't add new targets but they can still move the observer and existing target.

viewModel.start();

The LineOfSightViewModel also allows you to watch for changes (for example when the user moves the observer or the targets) and gives you access to the intersected graphic and the location where the intersection occurred. The observer is just a Point, so you can simply watch the observer property on the view model to know when an observer gets added or moved.

losViewModel.watch("observer", function(value) {
 // do something with the value
});

// watch when a target is added or removed
viewModel.targets.on("change", function(event) {
  // for each target watch when the intersected location changes
  event.added.forEach((target) => {
    target.watch("intersectedLocation", function() {
      // get access to intersected graphic and location
      if (target.intersectedGraphic) {
        // highlight the graphic
        lyrView.highlight(target.intersectedGraphic);
      }
      // get access to intersected location
      console.log(target.intersectedLocation);
    });
  });
});

A target contains information about the location of the target, whether it's visible or not, which graphic it intersects and the location where it intersects that graphic, an integrated mesh or the ground. The LineOfSightTarget class is used to represent a target.

See also

Constructors

new LineOfSightViewModel(properties)
Parameter
properties Object
optional

See the properties for a list of all the properties that may be passed into the constructor.

Property Overview

Any properties can be set, retrieved or listened to. See the Working with Properties topic.
Show inherited properties Hide inherited properties
Name Type Summary Class
LineOfSightAnalysis

The line of sight analysis object being created or modified by the view model.

more details
LineOfSightViewModel
String

The name of the class.

more details
Accessor
Point

The observer's viewpoint from which lines of sight will be drawn towards the targets.

more details
LineOfSightViewModel
String

The view model's state.

more details
LineOfSightViewModel
Collection<LineOfSightTarget>

A collection of LineOfSightTarget containing the target location and the analysis results.

more details
LineOfSightViewModel
SceneView

The view from which the widget will operate.

more details
LineOfSightViewModel

Property Details

analysis LineOfSightAnalysisautocastreadonly
Since: ArcGIS Maps SDK for JavaScript 4.23

The line of sight analysis object being created or modified by the view model.

This property can be set during view model construction, to provide an existing analysis to the view model for modification. Properties on the analysis can also be updated once it's assigned to the view model.

If no analysis is provided during view model construction, the view model automatically creates its own analysis and adds it to the view. In this case, the analysis will also be automatically removed from the view when the view model is destroyed.

Example
// Construct a line of sight analysis object outside of the view model
const analysis = new LineOfSightAnalysis({
  observer: {
    type: "point", // autocasts as new Point()
    x: 7.67,
    y: 45.981,
    z: 3435.765
  },
  targets: [{
    location: {
      type: "point",
      x: 7.659,
      y: 45.976,
      z: 4437
    }
  }]
});

// Ensure that the analysis is added to the view
view.analyses.add(analysis);

// Frame the analysis in the view
view.goTo(analysis.extent);

// Pass the analysis object as a constructor parameter to modify it using the view model
const viewModel = new LineOfSightViewModel({
  analysis: analysis,
  view: view
});
declaredClass Stringreadonly inherited

The name of the class. The declared class name is formatted as esri.folder.className.

observer Point

The observer's viewpoint from which lines of sight will be drawn towards the targets.

state Stringreadonly

The view model's state.

Value Description
disabled not ready yet
ready ready for analysis
creating observer/target points are being placed
created finished analysis

Possible Values:"disabled"|"ready"|"creating"|"created"

Default Value:disabled

A collection of LineOfSightTarget containing the target location and the analysis results.

view SceneView

The view from which the widget will operate.

Method Overview

Show inherited methods Hide inherited methods
Name Return Type Summary Class

Adds one or more handles which are to be tied to the lifecycle of the object.

more details
Accessor

Clears the current analysis results.

more details
LineOfSightViewModel

If stopped, this method continues the line of sight analysis and the user can add more targets.

more details
LineOfSightViewModel
Boolean

Returns true if a named group of handles exist.

more details
Accessor

Removes a group of handles owned by the object.

more details
Accessor

Starts a new line of sight analysis.

more details
LineOfSightViewModel

Stops the current line of sight analysis, keeping the results in the view.

more details
LineOfSightViewModel

Method Details

addHandles(handleOrHandles, groupKey)inherited
Since: ArcGIS Maps SDK for JavaScript 4.25

Adds one or more handles which are to be tied to the lifecycle of the object. The handles will be removed when the object is destroyed.

// Manually manage handles
const handle = reactiveUtils.when(
  () => !view.updating,
  () => {
    wkidSelect.disabled = false;
  },
  { once: true }
);

// Handle gets removed when the object is destroyed.
this.addHandles(handle);
Parameters
handleOrHandles WatchHandle|WatchHandle[]

Handles marked for removal once the object is destroyed.

groupKey *
optional

Key identifying the group to which the handles should be added. All the handles in the group can later be removed with Accessor.removeHandles(). If no key is provided the handles are added to a default group.

clear()

Clears the current analysis results. After calling this method, the user can set a new observer and targets.

continue()

If stopped, this method continues the line of sight analysis and the user can add more targets.

hasHandles(groupKey){Boolean}inherited
Since: ArcGIS Maps SDK for JavaScript 4.25

Returns true if a named group of handles exist.

Parameter
groupKey *
optional

A group key.

Returns
Type Description
Boolean Returns true if a named group of handles exist.
Example
// Remove a named group of handles if they exist.
if (obj.hasHandles("watch-view-updates")) {
  obj.removeHandles("watch-view-updates");
}
removeHandles(groupKey)inherited
Since: ArcGIS Maps SDK for JavaScript 4.25

Removes a group of handles owned by the object.

Parameter
groupKey *
optional

A group key or an array or collection of group keys to remove.

Example
obj.removeHandles(); // removes handles from default group

obj.removeHandles("handle-group");
obj.removeHandles("other-handle-group");
start()

Starts a new line of sight analysis.

stop()

Stops the current line of sight analysis, keeping the results in the view. Users can still interact with existing targets and the observer but they can't place new target points.

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