How can I make something move without floating after I release the move key?

Question

I'm new to Unity 5 and I've been trying to make a first project which is basically PONG, I got to the part where I want the player to move up when I press W, but the movement is floaty- the player continues to move abit after I release W.

     public KeyCode moveUp;
     public KeyCode moveDown;
     Vector2 movespeed = new Vector2 ();
     private Rigidbody2D rb;
 
     void Start()
     {
         movespeed.x = 0;
         rb = GetComponent<Rigidbody2D> ();
 
     }
     void Update () 
     {
         if (Input.GetKey (moveUp)) {
             movespeed.y = 10;
             rb.AddForce (movespeed);
         }
 
         else if (Input.GetKey (moveDown)) {
             movespeed.y = -10;
             rb.AddForce (movespeed);
         }
         else 
         {
             movespeed.y = 0;
             rb.AddForce (movespeed);
         }
     }

I tried accessing the velocity of RigidBody2D:

 rb.velocity.y = 10;

But it seems to work only in Unity 4.

Is there any way to make the object stop when releasing the move key?

Answer 1

Answer by M-Hanssen · Apr 18, 2016 at 02:39 PM

Set rigidbody to kinematic = true when you want to make it stop completely.

Don't forget to switch to kinematic = false when you move it again

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MelvMay ♦♦ · Apr 18, 2016 at 02:52 PM 1

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Changing the body type like this is non-trivial and is a mis-use. It causes all contacts to be deleted and re-calculated during the next fixed-update.

Answer 2

Answer by MelvMay · Apr 18, 2016 at 02:58 PM

 rb.velocity.y = 10;

This is a C# issue, it won't work in Unity 4 either. Velocity is a Vector2 value-type so you cannot set an individual component of it. When accessing it, you get a copy of the value-type (they are passed by-value).

To do this, you need to set the velocity to a whole new Vector2 like so:

 rb.velocity = new Vector2 (rb.velocity.x, 10.0f);

This is how C# works:

rb.velocity (returns a copy of the velocity Vector2)
rb.velocity.y = 10 (sets the Y of the copy of the velocity Vector2)

If you want to zero the velocity then you'd do this:

 rb.velocity = new Vector2.zero;

Note that by applying force in the 'Update' callback, you're doing it per-frame therefore you'll get different forces and speeds depending on the frame-rate. You should do this in the 'FixedUpdate' callback.

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itamariuser · Apr 18, 2016 at 03:23 PM 0

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It works! Thank you for taking the time to explain!

MelvMay ♦♦ itamariuser · Apr 18, 2016 at 03:26 PM 0

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Good to hear. Good luck!

Le-Pampelmuse MelvMay ♦♦ · Apr 18, 2016 at 05:18 PM 1

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Boom. Just made you a moderator! :P

How can I make something move without floating after I release the move key?

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