Display scenes in tabletop AR

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// Copyright 2020 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.

using ArcGISRuntime;
using ARKit;
using Esri.ArcGISRuntime.ARToolkit;
using Esri.ArcGISRuntime.Mapping;
using Foundation;
using System;
using UIKit;

namespace ArcGISRuntimeXamarin.Samples.DisplayScenesInTabletopAR
{
    [Register("DisplayScenesInTabletopAR")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Display scenes in tabletop AR",
        category: "Augmented reality",
        description: "Use augmented reality (AR) to pin a scene to a table or desk for easy exploration.",
        instructions: "You'll see a feed from the camera when you open the sample. Tap on any flat, horizontal surface (like a desk or table) to place the scene. With the scene placed, you can move the camera around the scene to explore. You can also pan and zoom with touch to adjust the position of the scene.",
        tags: new[] { "augmented reality", "drop", "mixed reality", "model", "pin", "place", "table-top", "tabletop" })]
    public class DisplayScenesInTabletopAR : UIViewController
    {
        // Hold references to UI controls.
        private ARSceneView _arSceneView;
        private UILabel _arKitStatusLabel;
        private UILabel _helpLabel;

        // Scene to be displayed on the tabletop.
        private Scene _tabletopScene;

        public DisplayScenesInTabletopAR()
        {
            Title = "Display scenes in tabletop AR";
        }

        public override void LoadView()
        {
            // Create the views.
            View = new UIView() { BackgroundColor = ApplicationTheme.BackgroundColor };

            _arSceneView = new ARSceneView();
            _arSceneView.TranslatesAutoresizingMaskIntoConstraints = false;

            _arKitStatusLabel = new UILabel();
            _arKitStatusLabel.TranslatesAutoresizingMaskIntoConstraints = false;
            _arKitStatusLabel.TextAlignment = UITextAlignment.Center;
            _arKitStatusLabel.TextColor = UIColor.Black;
            _arKitStatusLabel.BackgroundColor = UIColor.FromWhiteAlpha(1.0f, 0.6f);
            _arKitStatusLabel.Text = "Setting up ARKit";

            _helpLabel = new UILabel();
            _helpLabel.TranslatesAutoresizingMaskIntoConstraints = false;
            _helpLabel.TextAlignment = UITextAlignment.Center;
            _helpLabel.TextColor = UIColor.White;
            _helpLabel.BackgroundColor = UIColor.FromWhiteAlpha(0f, 0.6f);
            _helpLabel.Text = "Tap to place scene";
            _helpLabel.Hidden = true;

            // Add the views.
            View.AddSubviews(_arSceneView, _arKitStatusLabel, _helpLabel);

            // Lay out the views.
            NSLayoutConstraint.ActivateConstraints(new[]
            {
                _arSceneView.TopAnchor.ConstraintEqualTo(View.TopAnchor),
                _arSceneView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor),
                _arSceneView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _arSceneView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _arKitStatusLabel.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _arKitStatusLabel.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _arKitStatusLabel.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _arKitStatusLabel.HeightAnchor.ConstraintEqualTo(40),
                _helpLabel.BottomAnchor.ConstraintEqualTo(_arSceneView.SafeAreaLayoutGuide.BottomAnchor),
                _helpLabel.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _helpLabel.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _helpLabel.HeightAnchor.ConstraintEqualTo(40)
            });

            // Listen for tracking status changes and provide feedback to the user.
            _arSceneView.ARSCNViewCameraDidChangeTrackingState += ARSceneView_TrackingStateChanged;
        }

        private void Initialize()
        {
            // Display an empty scene to enable tap-to-place.
            _arSceneView.Scene = new Scene(SceneViewTilingScheme.WebMercator);

            // Render the scene invisible to start.
            _arSceneView.Scene.BaseSurface.Opacity = 0;

            // Get notification when planes are detected
            _arSceneView.PlanesDetectedChanged += ARSceneView_PlanesDetectedChanged;

            // Configure the AR scene view to render detected planes.
            _arSceneView.RenderPlanes = true;
        }

        private void ARSceneView_PlanesDetectedChanged(object sender, bool planeDetected)
        {
            if (planeDetected)
            {
                BeginInvokeOnMainThread(EnableTapToPlace);
                _arSceneView.PlanesDetectedChanged -= ARSceneView_PlanesDetectedChanged;
            }
        }

        private void EnableTapToPlace()
        {
            // Show the help label.
            _helpLabel.Hidden = false;
            _helpLabel.Text = "Tap to place the scene.";

            // Wait for the user to tap.
            _arSceneView.GeoViewTapped += _arSceneView_GeoViewTapped;
        }

        private void _arSceneView_GeoViewTapped(object sender, Esri.ArcGISRuntime.UI.Controls.GeoViewInputEventArgs e)
        {
            if (_arSceneView.SetInitialTransformation(e.Position))
            {
                DisplayScene();
                _arKitStatusLabel.Hidden = true;
            }
        }

        private async void DisplayScene()
        {
            // Hide the help label.
            _helpLabel.Hidden = true;

            if (_tabletopScene == null)
            {
                // Load a scene from ArcGIS Online.
                _tabletopScene = new Scene(new Uri("https://www.arcgis.com/home/item.html?id=31874da8a16d45bfbc1273422f772270"));
                await _tabletopScene.LoadAsync();

                // Set the clipping distance for the scene.
                _arSceneView.ClippingDistance = 400;

                // Enable subsurface navigation. This allows you to look at the scene from below.
                _tabletopScene.BaseSurface.NavigationConstraint = NavigationConstraint.None;

                _arSceneView.Scene = _tabletopScene;
            }

            // Create a camera at the bottom and center of the scene.
            //    This camera is the point at which the scene is pinned to the real-world surface.
            Camera originCamera = new Camera(52.52083, 13.40944, 8.813445091247559, 0, 90, 0);

            // Set the origin camera.
            _arSceneView.OriginCamera = originCamera;

            // The width of the scene content is about 800 meters.
            double geographicContentWidth = 800;

            // The desired physical width of the scene is 1 meter.
            double tableContainerWidth = 1;

            // Set the translation factor based on the scene content width and desired physical size.
            _arSceneView.TranslationFactor = geographicContentWidth / tableContainerWidth;
        }

        private void ARSceneView_TrackingStateChanged(object sender, ARSCNViewCameraTrackingStateEventArgs e)
        {
            // Provide clear feedback to the user in terms they will understand.
            switch (e.Camera.TrackingState)
            {
                case ARTrackingState.Normal:
                    _arKitStatusLabel.Hidden = true;
                    break;

                case ARTrackingState.NotAvailable:
                    _arKitStatusLabel.Hidden = false;
                    _arKitStatusLabel.Text = "ARKit location not available";
                    break;

                case ARTrackingState.Limited:
                    _arKitStatusLabel.Hidden = false;
                    switch (e.Camera.TrackingStateReason)
                    {
                        case ARTrackingStateReason.ExcessiveMotion:
                            _arKitStatusLabel.Text = "Try moving your device more slowly.";
                            break;

                        case ARTrackingStateReason.Initializing:
                            _arKitStatusLabel.Text = "Keep moving your device.";
                            break;

                        case ARTrackingStateReason.InsufficientFeatures:
                            _arKitStatusLabel.Text = "Try turning on more lights and moving around.";
                            break;

                        case ARTrackingStateReason.Relocalizing:
                            // This won't happen as this sample doesn't use relocalization.
                            break;
                    }

                    break;
            }
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            Initialize();
        }

        public override void ViewDidAppear(bool animated)
        {
            base.ViewDidAppear(animated);
            _arSceneView.StartTrackingAsync();
        }

        public override async void ViewDidDisappear(bool animated)
        {
            base.ViewDidDisappear(animated);

            if (_arSceneView != null)
            {
                _arSceneView.PlanesDetectedChanged -= ARSceneView_PlanesDetectedChanged;
                await _arSceneView.StopTrackingAsync();
            }
        }
    }
}