Show extruded features

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
// Copyright 2023 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
//
//   https://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 SwiftUI
import ArcGIS

struct ShowExtrudedFeaturesView: View {
    /// A scene with a topographic basemap centered on the US.
    @State private var scene: ArcGIS.Scene = makeScene()

    /// The population statistic selection of the picker.
    @State private var statisticSelection = Statistic.totalPopulation

    /// The feature layer on the scene.
    private var featureLayer: FeatureLayer {
        scene.operationalLayers.last as! FeatureLayer
    }

    var body: some View {
        VStack {
            SceneView(scene: scene)

            // Unit system picker.
            Picker("Statistic", selection: $statisticSelection) {
                ForEach(Statistic.allCases, id: \.self) { stat in
                    Text(stat.label)
                }
            }
            .pickerStyle(.segmented)
            .padding()
            .onChange(of: statisticSelection) { newValue in
                featureLayer.renderer?.sceneProperties.extrusionExpression = newValue.extrusionExpression
            }
        }
    }
}

private extension ShowExtrudedFeaturesView {
    /// Creates a scene with a feature layer.
    /// - Returns: A new `ArcGIS.Scene` object.
    private static func makeScene() -> ArcGIS.Scene {
        let scene = Scene(basemapStyle: .arcGISTopographic)

        // Set the scene view's viewpoint specified by the camera position.
        let point = Point(x: -99.659448, y: 20.513652, z: 12_940_924.0, spatialReference: .wgs84)
        let camera = Camera(lookingAt: point, distance: 0, heading: 0, pitch: 15, roll: 0)
        scene.initialViewpoint = Viewpoint(center: point, scale: .nan, camera: camera)

        // Add the extruded feature layer to the scene.
        scene.addOperationalLayer(makeFeatureLayer())
        return scene
    }

    /// Creates a feature layer from the US census feature service.
    /// - Returns: A new `FeatureLayer`
    private static func makeFeatureLayer() -> FeatureLayer {
        let featureTable = ServiceFeatureTable(url: .censusMapStates)
        let featureLayer = FeatureLayer(featureTable: featureTable)

        // Feature layer must be rendered dynamically for extrusion to work.
        featureLayer.renderingMode = .dynamic

        // Set the symbol used to display the features (US states) from the table.
        let fillSymbol = SimpleFillSymbol(
            style: .solid,
            color: .blue,
            outline: SimpleLineSymbol(color: .white.withAlphaComponent(0.5))
        )
        let renderer = SimpleRenderer(symbol: fillSymbol)

        // Set the renderer scene properties.
        renderer.sceneProperties.extrusionMode = .baseHeight
        renderer.sceneProperties.extrusionExpression = Statistic.totalPopulation.extrusionExpression

        // Set the renderer on the layer.
        featureLayer.renderer = renderer
        return featureLayer
    }
}

private extension ShowExtrudedFeaturesView {
    /// A enum for the different population statistics.
    enum Statistic: CaseIterable {
        case totalPopulation
        case populationDensity

        /// A human-readable label for the statistic.
        var label: String {
            switch self {
            case .totalPopulation:
                return "Total Population"
            case .populationDensity:
                return "Population Density"
            }
        }

        /// The extrusion expression for the statistic.
        var extrusionExpression: String {
            switch self {
            case .totalPopulation:
                return "[POP2007] / 10"
            case .populationDensity:
                // The offset makes the extrusion look better over Alaska.
                let offset = 100_000
                return "([POP07_SQMI] * 5000) + \(offset)"
            }
        }
    }
}

private extension URL {
    /// The States layer of the Census Map Service.
    static var censusMapStates: URL {
        URL(string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/3")!
    }
}

#Preview {
    ShowExtrudedFeaturesView()
}