AddForce in Update

Question

I want to add force during an animation clip (using OnStateUpdate which is the same as Update).

So, the question is: how to AddForce in the Update method properly as if it was the FixedUpdate?

Answer 1

If you want to ensure that you're reliably applying your physics forces during FixedUpdate() while simultaneously basing it on an animation that plays during Update(), you could use a Queue<> (or List<>, on the same general basis).

In short, you add forces to be applied during the animation, then "play them back" during the next FixedUpdate().

 Queue<Vector3> qForces = new Queue<Vector3>();
 
 // Simplified example call
 void OnStateUpdate(/*etc.*/)
 {
     // etc.
     qForces.Enqueue([FORCE_TO_APPLY]);
     // etc.
 }

 void FixedUpdate()
 {
     if(qForces.Count > 0) // Only worry about this when the queue isn't empty
     {
         Vector3 combinedForce = Vector3.zero;
         while(qForces.Count > 0)
         {
             combinedForce += qForces.Dequeue();
         }
         // Make only a single Rigidbody.AddForce() call using the
         // sum of all forces gathered between physics passes
         rb.AddForce(combinedForce, ForceMode.[Impulse/VelocityChange/etc.]);
     }
 }

^{Edit: Efficiency improvement}

AddForce in Update

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