How can I rotate a rigid body based on its velocity?

Question

Hi,

I have a tank that can fire a projectile(rigidbody) at an angle and force specified by the player. A pretty basic artillery game mechanic. The projectile fires in the correct direction but at the moment, left to the physics engine, the projectile(which is a capsule at the moment) doesn't rotate or "point" in the direction of travel as it moves through the air.

Does anyone know how I can achieve this effect?

Thanks

UPDATED 27/12/10

TankControl.cs (attached to the tank - projectile instantiation Method) shellSpawn is an empty gameobject that is a child of the tank gun barrel to spawn the projectile from.

void Fire() { //set the position and rotation of the projectile the the shell spawn point Vector3 position = shellSpawn.position; Quaternion rotation = shellSpawn.rotation;

 GameObject firedProjectile = (GameObject)Instantiate(shell, shellSpawn.position, shellSpawn.rotation);

 firedProjectile.rigidbody.AddRelativeForce(new Vector3(0,1,0) * gunPower, ForceMode.Impulse);

Projectile.cs (attached to projectile prefab - Update Method)

void Update () {
    transform.rotation = Quaternion.LookRotation(rigidbody.velocity);
}

Answer 1

Best Answer

Answer by Mickydtron · Dec 20, 2010 at 10:33 PM

transform.rotation=Quaternion.SetLookRotation(velocity);

This will set your rotation in the exact same direction that you are moving in. This assumes that you have a Vector3 velocity which you are using. It seems a fair assumption, all things considered.

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DanMarionette · Dec 27, 2010 at 04:59 PM 0

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Thanks for the reply, sorry it's been a while getting back to you but Christmas has taken over for the last week.

I have added what you have suggested to a script attached to the projectile prefab and it does look like its "trying" to do what I want but for my setup it isn't quite working. The projectile twists in the air. It's like it's rotating on two axis not just the one it should.

I have added the code to my question.

Mickydtron · Dec 27, 2010 at 10:49 PM 0

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I'm not sure what you're saying it's doing. so it currently points its nose in the direction of travel, but also spins around its own z axis? Is there any other code that could be affecting the rotation?

DanMarionette · Dec 30, 2010 at 05:24 PM 0

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I fixed the problem. It was due to non-uniform scaling on the prefab. With your answer it works perfectly now. Thanks.

Pivetta · Jun 19, 2019 at 05:05 PM 0

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Quaternion.SetLookRotation() is now a void method and works with this syntax:

 transform.rotation.SetLookRotation(velocity);

xxmark71xx Pivetta · May 15, 2021 at 05:25 PM 0

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Thank you. This works for me!

bionicartsmobile · Jun 17, 2020 at 07:39 AM 0

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This answer is great, but I have an extra question.

I want to

 transform.Rotate(-Input.acceleration.z, 0, 0);

AND Rotate towards rigid.velocity

 transform.rotation = Quaternion.LookRotation(rigid.velocity, Vector3.up);

How can I do both?

Answer 2

Answer by Bryan-Legend · May 01, 2015 at 06:35 PM

Here's the code that worked for me:

 transform.rotation = Quaternion.LookRotation(rigidbody.velocity);

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Answer 3

Answer by Elson · Aug 18, 2014 at 07:32 PM

//rotates rigidbody to face its current velocity public void RotateToVelocity(float turnSpeed, bool ignoreY) {
Vector3 dir; if(ignoreY) dir = new Vector3(rigidbody.velocity.x, 0f, rigidbody.velocity.z); else dir = rigidbody.velocity;

     if (dir.magnitude > 0.1)
     {
         Quaternion dirQ = Quaternion.LookRotation (dir);
         Quaternion slerp = Quaternion.Slerp (transform.rotation, dirQ, dir.magnitude * turnSpeed * Time.deltaTime);
         rigidbody.MoveRotation(slerp);
     }
 }

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How can I rotate a rigid body based on its velocity?

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