Stopping RigidBody on a dime

Unity Engine
1

Hello,
I’m making a bullet hell inspired game which require very precise control of character movement. I do want use a RigidBody over direct manipulation of transform.position because there will be some physics based collisions in the game. However, when the player stops pressing the arrow keys, I want the character to come to a complete stop instantly. Currently, the character comes to a stop more gradually, as if they are decelerating. I have tried doing things like increasing the drag, but that seems to just generally slow the character down. Here is the relevant code from my fixedUpdate:

float moveHorizontal = Input.GetAxis ("Horizontal");
        float moveVertical = Input.GetAxis ("Vertical");

        float horizontalspeed = moveHorizontal * maxSpeed;
        float verticalspeed = moveVertical * maxSpeed;

        //print (moving);

        if(moveHorizontal!=0 && moveVertical !=0)
        {
            horizontalspeed = horizontalspeed/Mathf.Sqrt(2);
            verticalspeed = verticalspeed/Mathf.Sqrt(2);   
        }

        if (Input.GetKeyUp ("up") || Input.GetKeyUp ("down")) {
                        print ("keyup");
            rigidbody2D.velocity = new Vector2 (horizontalspeed, 0f);

        }
            else
        rigidbody2D.velocity = new Vector2 (horizontalspeed, verticalspeed);

You can see that right now I’m testing just the vertical axis for a fix. I pass the vertical component of the Vector2 “0” when the key comes up. However despite this, it’s velocity still does not instantly drop to 0, instead it falls off. I don’t understand why at all. Any insight on how to fix this would be greatly appreciated. Thanks!

2

There is Input.GetAxisRaw(). its without smoothing.
http://docs.unity3d.com/ScriptReference/Input.GetAxisRaw.html

1 Like
3

I find the best thing to do is detect when there is no input and do this

if( noInput )
{
    rigidbody.AddForce( -rigidbody.velocity, ForceMode.VelocityChange );
}

I find that if you do things like

rigidbody.velocity = Vector3.zero;

then collision won’t always react as expected.

Edit:
I also just noticed you’re using the 2D system. So ignore everything I just said. I haven’t tried this with the 2D system.

2 Likes
4

i use often raw axis + smoothdamp and then smooth the current velocity to 0 if i have no input in that velocity direction.
if u set there a variable named damptime or somthing and use it as factor for the time argument then u can set it to like 0 or -1 an your chacater will stop instantly or u make just a bit smooth to avoid stucking movement

5

Ah, so the problem game from how I was doing input then? My current control method is keyboard so I assumed it would naturally be discreet/without smoothing. I’ll test this out and let you know if it worked. Thanks!

Edit: Works perfectly now. I was even able to remove the “GetKeyUp” part now that smoothing is completely removed. Thank you so much for your reply!

6

this works well for 3D, except it’s AddForce not AddVelocity… :wink:

1 Like
7

THANK YOU!

1 Like