Adjusted code in TwistChain constraints. Added intermediate step after

binder implementation.

Assets/AnimationRiggingWorkshop/Constraints/TwistChain.cs

             // Retrieve chain in-between root and tip transforms.
             Transform[] chain = ConstraintsUtils.ExtractChain(data.root, data.tip);
 
+            // Extract steps from chain.
+            float[] steps = ConstraintsUtils.ExtractSteps(chain);
+
             // Build Job.
             var job = new TwistChainJob();
             job.chain = new NativeArray<ReadWriteTransformHandle>(chain.Length, Allocator.Persistent, NativeArrayOptions.UninitializedMemory);
             job.tipTarget = ReadWriteTransformHandle.Bind(animator, data.tipTarget);
 
+            // Set values in NativeArray.
-            }
-
-            // Extract steps from chain.
-            float[] steps = ConstraintsUtils.ExtractSteps(chain);
-
-            // Update weights based on curve.
-            for (int i = 0; i < steps.Length; ++i)
-            {
                 job.steps[i] = steps[i];
                 job.weights[i] = Mathf.Clamp01(data.curve.Evaluate(steps[i]));
             }
         }
     }
 
-    [DisallowMultipleComponent, AddComponentMenu("SIGGRAPH 2019/Twist Chain")]
+    [DisallowMultipleComponent, AddComponentMenu("SIGGRAPH 2019/Twist Chain Final")]
     public class TwistChain : RigConstraint<
         TwistChainJob,
         TwistChainData,

Assets/AnimationRiggingWorkshop/Constraints/TwistChainStep0.cs

 
         public NativeArray<ReadWriteTransformHandle> chain;
 
+        public NativeArray<float> steps;
+
         public FloatProperty jobWeight { get; set; }
 
         public void ProcessRootMotion(AnimationStream stream) {}

Assets/AnimationRiggingWorkshop/Constraints/TwistChainStep1.cs

 
         public NativeArray<ReadWriteTransformHandle> chain;
 
+        public NativeArray<float> steps;
+
         public FloatProperty jobWeight { get; set; }
 
         public void ProcessRootMotion(AnimationStream stream) {}
-            // Retrieve root and tip rotation.
-            Quaternion rootRotation = rootTarget.GetRotation(stream);
-            Quaternion tipRotation = tipTarget.GetRotation(stream);
+            // 1. Retrieve root and tip rotation.
+            // ...
-            float mainWeight = jobWeight.Get(stream);
+            // 2. Interpolate rotation on chain.
+            // ...
-            // Interpolate rotation on chain.
-            for (int i = 0; i < chain.Length; ++i)
-            {
-                float weight = Mathf.InverseLerp(0, chain.Length - 1, i);
-                chain[i].SetRotation(stream, Quaternion.Lerp(chain[i].GetRotation(stream), Quaternion.Lerp(rootRotation, tipRotation, weight), mainWeight));
-            }
-
-            // Update position of tip handle for easier visualization.
-            rootTarget.SetPosition(stream, chain[0].GetPosition(stream));
-            tipTarget.SetPosition(stream, chain[chain.Length - 1].GetPosition(stream));
+            // 3. Update position of tip handle for easier visualization.
+            // ...
         }
     }
 
             // Retrieve chain in-between root and tip transforms.
             Transform[] chain = ConstraintsUtils.ExtractChain(data.root, data.tip);
 
+            // Extract steps from chain.
+            float[] steps = ConstraintsUtils.ExtractSteps(chain);
+
+            job.steps = new NativeArray<float>(chain.Length, Allocator.Persistent, NativeArrayOptions.UninitializedMemory);
+            // Set values in NativeArray.
+            {
+                job.steps[i] = steps[i];
+            }
 
             return job;
         }
-            job.chain.Dispose();
         }
 
         public override void Update(TwistChainStep1Job job, ref TwistChainStep1Data data)

Assets/AnimationRiggingWorkshop/Constraints/TwistChainStep1.cs.meta

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Assets/AnimationRiggingWorkshop/Scenes/TwistChainStep1.unity

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Assets/AnimationRiggingWorkshop/Constraints/TwistChainStep2.cs

+using System.Collections.Generic;
+using Unity.Collections;
+
+namespace UnityEngine.Animations.Rigging
+{
+    using Experimental.Animations;
+
+    [Unity.Burst.BurstCompile]
+    public struct TwistChainStep2Job : IWeightedAnimationJob
+    {
+        public ReadWriteTransformHandle rootTarget;
+        public ReadWriteTransformHandle tipTarget;
+
+        public NativeArray<ReadWriteTransformHandle> chain;
+
+        public NativeArray<float> steps;
+
+        public FloatProperty jobWeight { get; set; }
+
+        public void ProcessRootMotion(AnimationStream stream) {}
+
+        public void ProcessAnimation(AnimationStream stream)
+        {
+            // Retrieve root and tip rotation.
+            Quaternion rootRotation = rootTarget.GetRotation(stream);
+            Quaternion tipRotation = tipTarget.GetRotation(stream);
+
+            float mainWeight = jobWeight.Get(stream);
+
+            // Interpolate rotation on chain.
+            for (int i = 0; i < chain.Length; ++i)
+            {
+                chain[i].SetRotation(stream, Quaternion.Lerp(chain[i].GetRotation(stream), Quaternion.Lerp(rootRotation, tipRotation, steps[i]), mainWeight));
+            }
+
+            // Update position of tip handle for easier visualization.
+            rootTarget.SetPosition(stream, chain[0].GetPosition(stream));
+            tipTarget.SetPosition(stream, chain[chain.Length - 1].GetPosition(stream));
+        }
+    }
+
+    [System.Serializable]
+    public struct TwistChainStep2Data : IAnimationJobData
+    {
+        public Transform root;
+        public Transform tip;
+
+        [SyncSceneToStream] public Transform rootTarget;
+        [SyncSceneToStream] public Transform tipTarget;
+
+        bool IAnimationJobData.IsValid() => !(root == null || tip == null || !tip.IsChildOf(root) || rootTarget == null || tipTarget == null);
+
+        void IAnimationJobData.SetDefaultValues()
+        {
+            root = tip = rootTarget = tipTarget = null;
+        }
+    }
+
+    public class TwistChainStep2JobBinder : AnimationJobBinder<TwistChainStep2Job, TwistChainStep2Data>
+    {
+        public override TwistChainStep2Job Create(Animator animator, ref TwistChainStep2Data data, Component component)
+        {
+            // Retrieve chain in-between root and tip transforms.
+            Transform[] chain = ConstraintsUtils.ExtractChain(data.root, data.tip);
+
+            // Extract steps from chain.
+            float[] steps = ConstraintsUtils.ExtractSteps(chain);
+
+            // Build Job.
+            var job = new TwistChainStep2Job();
+            job.chain = new NativeArray<ReadWriteTransformHandle>(chain.Length, Allocator.Persistent, NativeArrayOptions.UninitializedMemory);
+            job.steps = new NativeArray<float>(chain.Length, Allocator.Persistent, NativeArrayOptions.UninitializedMemory);
+            job.rootTarget = ReadWriteTransformHandle.Bind(animator, data.rootTarget);
+            job.tipTarget = ReadWriteTransformHandle.Bind(animator, data.tipTarget);
+
+            // Set values in NativeArray.
+            for (int i = 0; i < chain.Length; ++i)
+            {
+                job.chain[i] = ReadWriteTransformHandle.Bind(animator, chain[i]);
+                job.steps[i] = steps[i];
+            }
+
+            return job;
+        }
+
+        public override void Destroy(TwistChainStep2Job job)
+        {
+            job.chain.Dispose();
+        }
+
+        public override void Update(TwistChainStep2Job job, ref TwistChainStep2Data data)
+        {
+        }
+    }
+
+    [DisallowMultipleComponent, AddComponentMenu("SIGGRAPH 2019/Twist Chain Step 2")]
+    public class TwistChainStep2 : RigConstraint<
+        TwistChainStep2Job,
+        TwistChainStep2Data,
+        TwistChainStep2JobBinder
+        >
+    {
+    }
+}

Assets/AnimationRiggingWorkshop/Constraints/TwistChainStep2.cs.meta

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