Add slingshot animation

VisualPinball.Engine.Test/Math/VectorTests.cs

@@ -51,5 +51,15 @@ public void ShouldCorrectlyCrossVectors()
 				.Should().BeEquivalentTo(new Vertex3D(-162.5f, -128.5f, 141.25f));
 		}
 
+		[Test]
+		public void ShouldCorrectlyLerpDragPoints()
+		{
+			var dp0 = new DragPointData(2f, 3f);
+			var dp1 = new DragPointData(8f, 12f);
+
+			dp0.Lerp(dp1, 0).Center.Should().Be(new Vertex3D(2f, 3f, 0f));
+			dp0.Lerp(dp1, 0.2f).Center.Should().Be(new Vertex3D(3.2f, 4.8f, 0f));
+			dp0.Lerp(dp1, 1).Center.Should().Be(new Vertex3D(8f, 12f, 0f));
+		}
 	}
 }

VisualPinball.Engine/Math/DragPointData.cs

@@ -20,6 +20,7 @@
 // ReSharper disable FieldCanBeMadeReadOnly.Global
 // ReSharper disable ConvertToConstant.Global
 // ReSharper disable CompareOfFloatsByEqualityOperator
+// ReSharper disable InconsistentNaming
 #endregion
 
 using System;
@@ -72,13 +73,33 @@ public override string ToString()
 			return $"DragPoint({Center.X}/{Center.Y}/{Center.Z}, {(IsSmooth ? "S" : "")}{(IsSlingshot ? "SS" : "")}{(HasAutoTexture ? "A" : "")})";
 		}
 
+		public DragPointData Lerp(DragPointData dp, float pos)
+		{
+			return new DragPointData(Center + pos * (dp.Center - Center)) {
+				IsSmooth = dp.IsSmooth,
+				IsSlingshot = dp.IsSlingshot,
+				HasAutoTexture = dp.HasAutoTexture,
+				TextureCoord = dp.TextureCoord,
+				IsLocked = dp.IsLocked,
+				EditorLayer = dp.EditorLayer,
+				EditorLayerName = dp.EditorLayerName,
+				EditorLayerVisibility = EditorLayerVisibility
+			};
+		}
+
 		#region BIFF
 
 		static DragPointData()
 		{
 			Init(typeof(DragPointData), Attributes);
 		}
 
+		public DragPointData(Vertex3D center) : base(null)
+		{
+			Center = center;
+			HasAutoTexture = true;
+		}
+
 		public DragPointData(float x, float y) : base(null)
 		{
 			Center = new Vertex3D(x, y, 0f);
@@ -112,5 +133,6 @@ public override void Write(BinaryWriter writer, HashWriter hashWriter)
 		private static readonly Dictionary<string, List<BiffAttribute>> Attributes = new Dictionary<string, List<BiffAttribute>>();
 
 		#endregion
+
 	}
 }

VisualPinball.Engine/VPT/Surface/SurfaceData.cs

@@ -97,13 +97,13 @@ public class SurfaceData : ItemData, ISurfaceData
 		public bool SlingshotAnimation = true;
 
 		[BiffFloat("ELAS", Pos = 20)]
-		public float Elasticity;
+		public float Elasticity = 0.3f;
 
 		[BiffFloat("ELFO", Pos = 21, WasAddedInVp107 = true)]
 		public float ElasticityFalloff;
 
 		[BiffFloat("WFCT", Pos = 22)]
-		public float Friction;
+		public float Friction = 0.3f;
 
 		[BiffFloat("WSCT", Pos = 23)]
 		public float Scatter;