Image recognition

Description

We will take advantage of arkit's built in ability to identify pre identified images in the scene.

This gives as another way of interacting with the real world environment.

Video

Code

using ARKit;
using SceneKit;
using System;
using UIKit;

namespace XamarinArkitSample
{
    public partial class ViewController : UIViewController
    {
        private readonly ARSCNView sceneView;

        public ViewController(IntPtr handle) : base(handle)
        {
            this.sceneView = new ARSCNView
            {
                AutoenablesDefaultLighting = true,
                Delegate = new SceneViewDelegate()
            };

            this.View.AddSubview(this.sceneView);
        }

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

            this.sceneView.Frame = this.View.Frame;
        }

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

            var detectionImages = ARReferenceImage.GetReferenceImagesInGroup("AR Resources", null);

            this.sceneView.Session.Run(new ARWorldTrackingConfiguration
            {
                AutoFocusEnabled = true,
                PlaneDetection = ARPlaneDetection.Horizontal | ARPlaneDetection.Vertical,
                LightEstimationEnabled = true,
                WorldAlignment = ARWorldAlignment.GravityAndHeading,
                DetectionImages = detectionImages,
                MaximumNumberOfTrackedImages = 1

            }, ARSessionRunOptions.ResetTracking | ARSessionRunOptions.RemoveExistingAnchors);
        }

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

            this.sceneView.Session.Pause();
        }

        public override void DidReceiveMemoryWarning()
        {
            base.DidReceiveMemoryWarning();
        }
    }

    public class SceneViewDelegate : ARSCNViewDelegate
    {
        public override void DidAddNode(ISCNSceneRenderer renderer, SCNNode node, ARAnchor anchor)
        {
            if (anchor is ARImageAnchor imageAnchor)
            {
                var detectedImage = imageAnchor.ReferenceImage;

                var width = detectedImage.PhysicalSize.Width;
                var length = detectedImage.PhysicalSize.Height;
                var planeNode = new PlaneNode(width, length, new SCNVector3(0, 0, 0), UIColor.Blue);

                float angle = (float)(-Math.PI / 2);
                planeNode.EulerAngles = new SCNVector3(angle, 0, 0);

                node.AddChildNode(planeNode);
            }
        }

        public override void DidRemoveNode(ISCNSceneRenderer renderer, SCNNode node, ARAnchor anchor)
        {
            if (anchor is ARPlaneAnchor planeAnchor)
            {
            }
        }

        public override void DidUpdateNode(ISCNSceneRenderer renderer, SCNNode node, ARAnchor anchor)
        {
            if (anchor is ARPlaneAnchor planeAnchor)
            {
            }
        }
    }

    public class PlaneNode : SCNNode
    {
        public PlaneNode(nfloat width, nfloat length, SCNVector3 position, UIColor colour)
        {
            var rootNode = new SCNNode
            {
                Geometry = CreateGeometry(width, length, colour),
                Position = position
            };

            AddChildNode(rootNode);
        }

        private static SCNGeometry CreateGeometry(nfloat width, nfloat length, UIColor colour)
        {
            var material = new SCNMaterial();
            material.Diffuse.Contents = colour;
            material.DoubleSided = false;

            var geometry = SCNPlane.Create(width, length);
            geometry.Materials = new[] { material };

            return geometry;
        }
    }
}