Opacity

Description

We can control how transparent or opaque an element in our scene is using the .Opacity property where 0.1f is 10% opaque and 1f is 100% opaque.

Opacity is a float and by default is 1f (100% opaque).

Video

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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
            };

            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);

            this.sceneView.Session.Run(new ARWorldTrackingConfiguration
            {
                AutoFocusEnabled = true,
                PlaneDetection = ARPlaneDetection.Horizontal,
                LightEstimationEnabled = true,
                WorldAlignment = ARWorldAlignment.GravityAndHeading
            }, ARSessionRunOptions.ResetTracking | ARSessionRunOptions.RemoveExistingAnchors);

            var size = 0.09f;
            var colour = UIColor.Purple;
            var topRowY = 0.1f;
            var bottomRowY = 0f;

            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(-0.2f, topRowY, 0), 1.0f));
            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(-0.1f, topRowY, 0), 0.9f));
            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(0, topRowY, 0), 0.8f));
            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(0.1f, topRowY, 0), 0.7f));
            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(0.2f, topRowY, 0), 0.6f));

            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(-0.2f, bottomRowY, 0), 0.5f));
            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(-0.1f, bottomRowY, 0), 0.4f));
            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(0f, bottomRowY, 0), 0.3f));
            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(0.1f, bottomRowY, 0), 0.2f));
            this.sceneView.Scene.RootNode.AddChildNode(new PlaneNode(size, colour, new SCNVector3(0.2f, bottomRowY, 0), 0.1f));
        }

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

            this.sceneView.Session.Pause();
        }

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

    public class PlaneNode : SCNNode
    {
        public PlaneNode(float size, UIColor color, SCNVector3 position, float opacity)
        {
            var rootNode = new SCNNode
            {
                Geometry = CreateGeometry(size, color),
                Position = position,
                Opacity = opacity
            };

            AddChildNode(rootNode);
        }

        private static SCNGeometry CreateGeometry(float size, UIColor color)
        {
            var material = new SCNMaterial();
            material.Diffuse.Contents = color;

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

            return geometry;
        }
    }
}