Extrude graphics

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//
// Copyright 2016 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 ExtrudeGraphicsViewController: UIViewController {
    @IBOutlet var sceneView: AGSSceneView!

    private let graphicsOverlay = AGSGraphicsOverlay()

    private let cameraStartingPoint = AGSPoint(x: 83, y: 28.4, z: 20000, spatialReference: .wgs84())
    private let squareSize: Double = 0.01
    private let spacing: Double = 0.01
    private let maxHeight = 10000

    override func viewDidLoad() {
        super.viewDidLoad()

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

        // Initialize scene with topographic basemap style.
        let scene = AGSScene(basemapStyle: .arcGISTopographic)
        // assign scene to the scene view
        self.sceneView.scene = scene

        // set the viewpoint camera
        let camera = AGSCamera(location: self.cameraStartingPoint, heading: 10, pitch: 70, roll: 0)
        self.sceneView.setViewpointCamera(camera)

        // add graphics overlay
        graphicsOverlay.sceneProperties?.surfacePlacement = .drapedBillboarded
        self.sceneView.graphicsOverlays.add(graphicsOverlay)

        // simple renderer with extrusion property
        let renderer = AGSSimpleRenderer()
        let lineSymbol = AGSSimpleLineSymbol(style: .solid, color: .white, width: 1)
        renderer.symbol = AGSSimpleFillSymbol(style: .solid, color: .accentColor, outline: lineSymbol)
        renderer.sceneProperties?.extrusionMode = .baseHeight
        renderer.sceneProperties?.extrusionExpression = "[height]"
        self.graphicsOverlay.renderer = renderer

        // add base surface for elevation data
        let surface = AGSSurface()
        /// The url of the Terrain 3D ArcGIS REST Service.
        let worldElevationServiceURL = URL(string: "https://elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer")!
        let elevationSource = AGSArcGISTiledElevationSource(url: worldElevationServiceURL)
        surface.elevationSources.append(elevationSource)
        scene.baseSurface = surface

        // add the graphics
        self.addGraphics()
    }

    private func addGraphics() {
        // starting point
        let x = cameraStartingPoint.x - 0.01
        let y = cameraStartingPoint.y + 0.25

        // creating a grid of polygon graphics
        for column in stride(from: 0.0, through: 6.0, by: 1.0) {
            for row in stride(from: 0.0, through: 4.0, by: 1.0) {
                let startingX = x + column * (squareSize + spacing)
                let startingY = y + row * (squareSize + spacing)
                let startingPoint = AGSPoint(x: startingX, y: startingY, spatialReference: nil)
                let polygon = polygonForStartingPoint(startingPoint)
                addGraphicForPolygon(polygon)
            }
        }
    }

    // the function returns a polygon starting at the given point
    // with size equal to squareSize
    private func polygonForStartingPoint(_ point: AGSPoint) -> AGSPolygon {
        let polygon = AGSPolygonBuilder(spatialReference: .wgs84())
        polygon.addPointWith(x: point.x, y: point.y)
        polygon.addPointWith(x: point.x, y: point.y + squareSize)
        polygon.addPointWith(x: point.x + squareSize, y: point.y + squareSize)
        polygon.addPointWith(x: point.x + squareSize, y: point.y)
        return polygon.toGeometry()
    }

    // add a graphic to the graphics overlay for the given polygon
    private func addGraphicForPolygon(_ polygon: AGSPolygon) {
        let rand = Int.random(in: 0...maxHeight)

        let graphic = AGSGraphic(geometry: polygon, symbol: nil, attributes: nil)
        graphic.attributes.setValue(rand, forKey: "height")
        self.graphicsOverlay.graphics.add(graphic)
    }
}