Rigidbody2D and ForceMode.AddVelocity?

Question

The new 2D update (Unity v4.3, released 2013-11-12) have come with the new Rigidbody2D component.

My previous code uses the 3D-based rigidbody, moving it using Rigidbody.AddForce(). I specified that the AddForce() uses ForceMode.VelocityChange, which conveniently ignores mass and just makes it better for a playable character.

Rigidbody2D.AddForce() on the other hand does not support ForceMode at all, it has only one way of dealing with velocity and that is 'force = mass * acceleration'.

Here's the part of my code that applies the target velocity to the rigidbody:

             /* Apply motion */
             Vector3 _velocity = myRigidbody.velocity;
             Vector3 _velocityChange = (TargetVelocity - _velocity);
 
             /* Move rigidbody */
             myRigidbody.AddForce(_velocityChange,ForceMode.VelocityChange);

How to convert this movement to the Rigidbody2D? Preferably I am looking for an identical conversion, as I am quite keen on how the character feels right now when moving.

Answer 1

Best Answer

Answer by s_guy · Nov 14, 2013 at 02:10 AM

Yeah, no forcemodes (yet?) on Rigidbody2D. However, you should be able to the same result as ForceMode.VelocityChange by just adding your new velocity to the rigidbody2D.velocity.

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Andrige_ · Nov 14, 2013 at 01:00 PM 0

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Thank you! That works just as I had hoped.

Answer 2

Here are some extension methods for Physics2D to add this missing functionality to AddForce, strongly based on the solution by gfoot at this thread.

 public static class Physics2DExtensions {
     public static void AddForce (this Rigidbody2D rigidbody2D, Vector2 force, ForceMode mode = ForceMode.Force) {
         switch (mode) {
         case ForceMode.Force:
             rigidbody2D.AddForce (force);
             break;
         case ForceMode.Impulse:
             rigidbody2D.AddForce (force / Time.fixedDeltaTime);
             break;
         case ForceMode.Acceleration:
             rigidbody2D.AddForce (force * rigidbody2D.mass);
             break;
         case ForceMode.VelocityChange:
             rigidbody2D.AddForce (force * rigidbody2D.mass / Time.fixedDeltaTime);
             break;
         }
     }
     
     public static void AddForce (this Rigidbody2D rigidbody2D, float x, float y, ForceMode mode = ForceMode.Force) {
         rigidbody2D.AddForce (new Vector2 (x, y), mode);
     }
 }

Answer 3

Answer by slake_it · Mar 02, 2016 at 10:00 AM

Force mode has been added 2d rigidbodies

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XenoRo · Jun 30, 2017 at 08:18 PM 0

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As of version 5.61f1, still only half-implemented, and missing the mass-ignoring modes (Acceleration and VelocityChange)... Sincerely, can't see why unity doesn't use the good old Force$$anonymous$$ode type for both 3D and 2D.

Rigidbody2D and ForceMode.AddVelocity?

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