// Highlight the node at index 'index' by setting a CI filter
        private void HighlightContact(int index, PresentationViewController presentationViewController)
        {
            // Create a filter
            var glowFilter = new SCGlowFilter();

            glowFilter.Name = "aGlow";
            glowFilter.SetDefaults();

            // Retrieve the node to highlight
            // Scale up and move to front a little
            var contactNode = GroupNode.FindChildNode("contact" + index, true);

            contactNode.Scale    = new SCNVector3(1.2f, 1.2f, 1.2f);
            contactNode.Position = new SCNVector3(contactNode.Position.X, contactNode.Position.Y, contactNode.Position.Z + 50);

            // Compute the screenspace position of this node because the glow filter needs this info
            var worldPosition          = contactNode.ConvertPositionToNode(new SCNVector3(0, 0, 0), null);
            var screenPosition         = ((SCNView)presentationViewController.View).ProjectPoint(worldPosition);
            var screenPositionInPixels = ((SCNView)presentationViewController.View).ConvertPointToBacking(new CGPoint(screenPosition.X, screenPosition.Y));

            glowFilter.CenterX = screenPositionInPixels.X;
            glowFilter.CenterY = screenPositionInPixels.Y;

            glowFilter.InputRadius = new NSNumber(10);

            // Set the filter
            // TODO contactNode.Filters = new CIFilter[] { glowFilter };

            // Animate the radius parameter of the glow filter

            /* TODO CABasicAnimation animation = CABasicAnimation.FromKeyPath ("filters.aGlow.inputRadius");
             * animation.To = new NSNumber (20);
             * animation.From = new NSNumber (10);
             * animation.AutoReverses = true;
             * animation.RepeatCount = float.MaxValue;
             * animation.Duration = 1.0f;
             * animation.TimingFunction = CAMediaTimingFunction.FromName (CAMediaTimingFunction.EaseInEaseOut);
             * contactNode.AddAnimation (animation, new NSString ("filterAnimation"));*/
        }
		// Highlight the node at index 'index' by setting a CI filter
		private void HighlightContact (int index, PresentationViewController presentationViewController)
		{
			// Create a filter
			var glowFilter = new SCGlowFilter ();
			glowFilter.Name = "aGlow";
			glowFilter.SetDefaults ();

			// Retrieve the node to highlight
			// Scale up and move to front a little
			var contactNode = GroupNode.FindChildNode ("contact" + index, true);
			contactNode.Scale = new SCNVector3 (1.2f, 1.2f, 1.2f);
			contactNode.Position = new SCNVector3 (contactNode.Position.X, contactNode.Position.Y, contactNode.Position.Z + 50);

			// Compute the screenspace position of this node because the glow filter needs this info
			var worldPosition = contactNode.ConvertPositionToNode (new SCNVector3 (0, 0, 0), null);
			var screenPosition = ((SCNView)presentationViewController.View).ProjectPoint (worldPosition);
			var screenPositionInPixels = ((SCNView)presentationViewController.View).ConvertPointToBacking (new CGPoint (screenPosition.X, screenPosition.Y));

			glowFilter.CenterX = screenPositionInPixels.X;
			glowFilter.CenterY = screenPositionInPixels.Y;

			glowFilter.InputRadius = new NSNumber (10);

			// Set the filter
			// TODO contactNode.Filters = new CIFilter[] { glowFilter };

			// Animate the radius parameter of the glow filter
			/* TODO CABasicAnimation animation = CABasicAnimation.FromKeyPath ("filters.aGlow.inputRadius");
			animation.To = new NSNumber (20);
			animation.From = new NSNumber (10);
			animation.AutoReverses = true;
			animation.RepeatCount = float.MaxValue;
			animation.Duration = 1.0f;
			animation.TimingFunction = CAMediaTimingFunction.FromName (CAMediaTimingFunction.EaseInEaseOut);
			contactNode.AddAnimation (animation, new NSString ("filterAnimation"));*/
		}