Improve ARKit face demo

ARKit/ARKitXamarinDemo/FaceDemo.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Linq;
 using ARKit;
 using Urho;
 using Urho.iOS;
@@ -54,22 +55,85 @@ void ArkitComponent_DidRemoveAnchors(ARAnchor[] anchors)
 			}
 		}
 
-		void UpdateAnchor(Node node, ARAnchor anchor)
+		unsafe void UpdateAnchor(Node node, ARAnchor anchor)
 		{
 			var faceAnchor = anchor as ARFaceAnchor;
 			if (faceAnchor == null)
 				return;
 
+			StaticModel faceModel;
+
 			if (node == null)
 			{
 				var id = faceAnchor.Identifier.ToString();
 				node = anchorsNode.CreateChild(id);
-				var faceBoxNode = node.CreateChild();
-				var box = faceBoxNode.CreateComponent<Urho.Shapes.Box>();
-				faceBoxNode.Scale = new Vector3(0.15f, 0.15f, 0.01f);
+				faceModel = node.CreateComponent<StaticModel>();
+			}
+			else
+				faceModel = node.GetComponent<StaticModel>();
+
+			arkitComponent.ApplyOpenTkTransform(node, faceAnchor.Transform, true);
+
+			var faceGeom = faceAnchor.Geometry;
+			var finalVertices = faceGeom.GetVertices()
+					.Select(v => new VertexBuffer.PositionNormalColor
+					{
+						Color = Color.Green.ToUInt(),
+						Position = new Vector3(v.X, v.Y, -v.Z)
+					}).ToArray();
+
+			// calculate normals
+			var indices = faceGeom.GetTriangleIndices();
+			for (int i = 0; i < indices.Length; i += 3)
+			{
+				ref var v1 = ref finalVertices[indices[i]];
+				ref var v2 = ref finalVertices[indices[i + 1]];
+				ref var v3 = ref finalVertices[indices[i + 2]];
+
+				Vector3 edge1 = v1.Position - v2.Position;
+				Vector3 edge2 = v1.Position - v3.Position;
+
+				var normal = Vector3.Cross(edge1, edge2);
+				normal = new Vector3(normal.X, -normal.Y, -normal.Z);
+				normal.Normalize();
+
+				v1.Normal = normal;
+				v2.Normal = normal;
+				v3.Normal = normal;
+			}
+			var model = new Model();
+			var vertexBuffer = new VertexBuffer(Context, false);
+			var indexBuffer = new IndexBuffer(Context, false);
+			var geometry = new Geometry();
+
+
+			vertexBuffer.Shadowed = true;
+			vertexBuffer.SetSize((uint)faceGeom.VertexCount, ElementMask.Position | ElementMask.Normal | ElementMask.Color, true);
+
+			fixed (VertexBuffer.PositionNormalColor* p = &finalVertices[0])
+				vertexBuffer.SetData((void*)p);
+
+			indexBuffer.Shadowed = true;
+			indexBuffer.SetSize((uint)indices.Length, false, true);
+			indexBuffer.SetData(indices);
+
+			geometry.SetVertexBuffer(0, vertexBuffer);
+			geometry.IndexBuffer = indexBuffer;
+			geometry.SetDrawRange(PrimitiveType.TriangleList, 0, (uint)indices.Length, 0, (uint)faceGeom.VertexCount, true);
+
+			model.NumGeometries = 1;
+			model.SetGeometry(0, 0, geometry);
+			model.BoundingBox = new BoundingBox(-Vector3.One * 0.01f, Vector3.One * 0.01f);
+			faceModel.Model = model;
+
+			if (faceModel.Material == null)
+			{
+				var mat = new Material();
+				mat.SetTechnique(0, CoreAssets.Techniques.NoTextureVCol, 0);
+				mat.CullMode = CullMode.Cw;
+				faceModel.SetMaterial(0, mat);
 			}
 
-			arkitComponent.ApplyOpenTkTransform(node, faceAnchor.Transform);
 		}
 	}
 }

ARKit/ARKitXamarinDemo/VerticalSurfaces.cs

@@ -34,7 +34,7 @@ protected override void Start()
 			arkitComponent.ARConfiguration = new ARWorldTrackingConfiguration {
 				PlaneDetection = 
 				ARPlaneDetection.Horizontal
-#if false // uncomment once Xamarin.iOS with xcode93 is released:
+#if true // requires Xamarin.IOS with xcode93 support
 				| ARPlaneDetection.Vertical,
 #endif
 			};