How to add opposite force of current direction?

Question

I making Space shooter game, camera looking from bird view, my space ship turning around and goes in all direction by AddForce fucntion. i want to add braking sistem to decresing addforce in current direction until it reach zero. :) can you write me that code?

this is my script

 var speed : float = 10;
 var rotationSpeed: float = 10;
 var sideForce : float = 20;
 var topSpeed : float = 20;
 
 function Update()
 {
     //Controls for ship...
     if(Input.GetKey("s") || Input.GetKey("0"))
     {
         rigidbody.AddRelativeForce(Vector3.back * speed * Time.deltaTime);
     }
     if(Input.GetKey("w") || Input.GetKey("1"))
     {
         rigidbody.AddRelativeForce(Vector3.forward * speed * Time.deltaTime);
     }
     
         if(Input.GetKey("q") || Input.GetKey("0"))
     {
         rigidbody.AddRelativeForce(Vector3.left * sideForce * Time.deltaTime);
     }
     
         if(Input.GetKey("e") || Input.GetKey("0"))
     {
         rigidbody.AddRelativeForce(Vector3.right * sideForce * Time.deltaTime);
     }
     
         if(Input.GetKey("a"))
     {
         transform.Rotate(Vector3.down * rotationSpeed * Time.deltaTime);
     }
     
         if(Input.GetKey("d"))
     {
         transform.Rotate(Vector3.up * rotationSpeed * Time.deltaTime);
     }
 }

Answer 1

Answer by rutter · Jul 17, 2014 at 12:35 AM

The rigidbody has a velocity vector indicating the direction and speed of its current movement.

If you want another vector pointing in the opposite direction? Just multiply by negative one. :)

 var opposite = -rigidbody.velocity;
 rigidbody.AddForce(opposite * Time.deltaTime);

Maybe you want to control how hard you brake?

 var opposite = -rigidbody.velocity;
 var brakePower = 10;
 var brakeForce = opposite.normalized * brakePower;
 rigidbody.AddForce(brakeForce * Time.deltaTime);

The above might end up pushing backwards, when you're almost stopped.

You could also scale down velocity:

 var curSpeed = rigidbody.velocity.magnitude;
 var newSpeed = curSpeed - 10 * Time.deltaTime;
 if (newSpeed < 0) {
     newSpeed = 0;
 }
 rigidbody.velocity = rigidbody.velocity.normalized * newSpeed;

In this specific example, it might be simplest to simulate a brake by increasing the rigidbody's drag:

 if (braking) {
     rigidbody.drag = 20;
 } else {
     rigidbody.drag = 5;
 }

If any of this confuses you, I suggest reading up on the Vector3 and Rigidbody manual pages.

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jure006 · Jul 17, 2014 at 06:04 AM 0

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yeea, very interested codes. That 2nd code is exactly what i needed, you solved my problem, thank you man so so much! :)

tcz8 jure006 · Sep 03, 2020 at 03:59 AM 0

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Good code indeed, Thank you! @jure006 you should accept his answer, he deserves it.

Shishigami · May 22, 2017 at 02:11 PM 1

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Is there a way to convert this into c#? I dont really have that much understanding of Javascript, but i have the exact same problem. :P

Answer 2

Answer by Shishigami · May 24, 2017 at 07:44 AM

Is there a way to convert this into c#? I dont really have that much understanding of Javascript, but i have the exact same problem. :P

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Hamilcar-games · Aug 18, 2018 at 02:12 PM 1

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its c# just add in start method getcomponent rigidbody

How to add opposite force of current direction?

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