Viewshed (GeoElement)

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// Copyright 2017 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import UIKit
import ArcGIS

class ViewshedGeoElementViewController: UIViewController, AGSGeoViewTouchDelegate {
    @IBOutlet var sceneView: AGSSceneView!
    var tank = AGSGraphic()
    var waypoint: AGSPoint?
    var animationTimer: Timer?

    override func viewDidLoad() {
        super.viewDidLoad()

        // Add the source code button item to the right of navigation bar
        (navigationItem.rightBarButtonItem as! SourceCodeBarButtonItem).filenames = ["ViewshedGeoElementViewController"]

        // set the sceneView's touch delegate so we can get user taps
        sceneView.touchDelegate = self

        let graphicsOverlay = makeGraphicsOverlay()
        sceneView.graphicsOverlays.add(graphicsOverlay)

        let analysisOverlay = makeAnalysisOverlay()
        sceneView.analysisOverlays.add(analysisOverlay)

        let cameraController = makeCameraController()
        sceneView.cameraController = cameraController

        sceneView.scene = makeScene()
    }

    private func makeScene() -> AGSScene {
        // create the scene
        let scene = AGSScene(basemapStyle: .arcGISImagery)

        // add base surface for elevation data
        let surface = AGSSurface()
        /// The url of the image service for elevation in Brest, France.
        let brestElevationServiceURL = URL(string: "https://scene.arcgis.com/arcgis/rest/services/BREST_DTM_1M/ImageServer")!
        let elevationSource = AGSArcGISTiledElevationSource(url: brestElevationServiceURL)
        surface.elevationSources.append(elevationSource)
        scene.baseSurface = surface

        /// The url of the scene service for buildings in Brest, France.
        let brestBuildingsServiceURL = URL(string: "https://tiles.arcgis.com/tiles/P3ePLMYs2RVChkJx/arcgis/rest/services/Buildings_Brest/SceneServer/layers/0")!
        // add a scene layer
        let buildings = AGSArcGISSceneLayer(url: brestBuildingsServiceURL)
        scene.operationalLayers.add(buildings)

        return scene
    }

    private func makeGraphicsOverlay() -> AGSGraphicsOverlay {
        // create a graphics overlay for the tank
        let graphicsOverlay = AGSGraphicsOverlay()
        graphicsOverlay.sceneProperties = AGSLayerSceneProperties(surfacePlacement: .relative)

        // set up heading expression for tank
        let renderer3D = AGSSimpleRenderer()
        let sceneProperties = AGSRendererSceneProperties(headingExpression: "[heading] + 90", pitchExpression: "[pitch]", rollExpression: "[roll]")
        sceneProperties.headingExpression = "[HEADING]"
        renderer3D.sceneProperties = sceneProperties
        graphicsOverlay.renderer = renderer3D

        // create a graphic of a tank
        let tankSymbol = AGSModelSceneSymbol(name: "bradle", extension: "3ds", scale: 10.0)
        tankSymbol.heading = 90.0
        tankSymbol.anchorPosition = .bottom
        tank = AGSGraphic(
            geometry: AGSPoint(x: -4.506390,
                               y: 48.385624,
                               spatialReference: .wgs84()),
            symbol: tankSymbol,
            attributes: ["HEADING": 0.0]
        )
        graphicsOverlay.graphics.add(tank)
        return graphicsOverlay
    }

    private func makeAnalysisOverlay() -> AGSAnalysisOverlay {
        // create a viewshed to attach to the tank
        let geoElementViewshed = AGSGeoElementViewshed(
           geoElement: tank,
           horizontalAngle: 90.0,
           verticalAngle: 40.0,
           minDistance: 0.1,
           maxDistance: 250.0,
           headingOffset: 0.0,
           pitchOffset: 0.0
        )

        // offset viewshed observer location to top of tank
        geoElementViewshed.offsetZ = 3.0

        // create an analysis overlay to add the viewshed to the scene view
        let analysisOverlay = AGSAnalysisOverlay()
        analysisOverlay.analyses.add(geoElementViewshed)
        return analysisOverlay
    }

    private func makeCameraController() -> AGSCameraController {
        // set camera controller to follow tank
        let cameraController = AGSOrbitGeoElementCameraController(targetGeoElement: tank, distance: 200.0)
        cameraController.cameraPitchOffset = 45.0
        return cameraController
    }

    func geoView(_ geoView: AGSGeoView, didTapAtScreenPoint screenPoint: CGPoint, mapPoint: AGSPoint) {
        // set the new waypoint
        waypoint = mapPoint

        // start a timer to animate towards the waypoint
        animationTimer = Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true) { [weak self] _ in
            self?.animate()
        }
    }

    private func animate() {
        guard let waypoint = waypoint,
            let location = tank.geometry as? AGSPoint else { return }

        guard let distanceResult = AGSGeometryEngine.geodeticDistanceBetweenPoint1(location,
                                                                                   point2: waypoint,
                                                                                   distanceUnit: AGSLinearUnit.meters(),
                                                                                   azimuthUnit: AGSAngularUnit.degrees(),
                                                                                   curveType: .geodesic) else { return }

        // move toward waypoint a short distance
        let locations = AGSGeometryEngine.geodeticMove([location],
                                                       distance: 1.0,
                                                       distanceUnit: AGSLinearUnit.meters(),
                                                       azimuth: distanceResult.azimuth1,
                                                       azimuthUnit: distanceResult.azimuthUnit ?? AGSAngularUnit.degrees(),
                                                       curveType: .geodesic)

        if let newLocation = locations?.first {
            tank.geometry = newLocation
        }

        if let heading = tank.attributes["HEADING"] as? Double {
            tank.attributes["HEADING"] = heading + ((distanceResult.azimuth1 - heading) / 10)
        }

        // stop the animation when we're within 5 meters of the waypoint
        if distanceResult.distance <= 5 {
            self.waypoint = nil
            animationTimer?.invalidate()
        }
    }
}