Add force relative to camera direction?

Question

How could I set this up so that it adds the force relative to the camera's direction instead of world? Currently have this attached to a ball object and slightly modified orbit script attached to camera.

 function FixedUpdate () {
     var dir : Vector3 = Vector3.zero;
     
     dir.x = Input.GetAxis("Horizontal");
     dir.z = Input.GetAxis("Vertical");
     
     rigidbody.AddForce(dir * force);
 }

I was thinking something like below, but that doesn't seem to work.

 function FixedUpdate () {
     var camdir : Vector3 = camera.forward;
     var dir : Vector3 = Vector3.zero;
 
     dir.x = Input.GetAxis("Horizontal");
     dir.z = Input.GetAxis("Vertical");
     
     var relativedir : Vector3 = Vector3.Cross(camdir, dir);
     rigidbody.AddForce(relativedir * force);
 }

Edit: came up with this, it partially works. The only problem is that it doesn't seem to like diagonal directions. If I rotate the camera 30 degrees to left and push forward, it will go towards 0 degrees. If I rotate camera 60 degrees and push forward, it goes towards 90 degrees.

 function Update() {
     var camDir : Vector3 = Camera.main.transform.forward;
     
     
     var inputDir : Vector3 = Vector3.zero;
     inputDir.x = Input.GetAxis("Left_Horizontal");
     inputDir.z = Input.GetAxis("Left_Vertical");
     
     var dir : Vector3 = Vector3.zero;
     dir.x = camDir.x * inputDir.x;
     dir.z = camDir.z * inputDir.z;
     
     rigidbody.AddForce(dir * force);
 }

Answer 1

Best Answer

Answer by syclamoth · Jan 20, 2012 at 03:50 AM

Given that you have the transform of the camera, you can always use this-

 var controlDirection : Vector3 = Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
 var actualDirection = cameraTransform.TransformDirection(controlDirection);

Then, you have camera-relative directions! You may want to flatten it to the x-z plane if you want your character to walk around flat, but you might not.

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iamevn · Jan 20, 2012 at 04:08 AM 0

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That doesn't really change much. I probably should have clairified that camera had the Camera.main's transform assigned to it.

syclamoth · Jan 20, 2012 at 04:23 AM 0

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Fixed my answer. Sorry, didn't quite understand the question!

iamevn · Jan 20, 2012 at 04:27 AM 0

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thanks! works great.

nobluff67 · Aug 31, 2019 at 04:26 PM 0

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Works really well for such a frustrating concept. I have been struggling to find such and easy and elegant solution.

Answer 2

Answer by Imaginaire · Aug 20, 2012 at 11:55 AM

I know this was posted a long time ago, but just for others who might look here.

Change rigidbody.AddForce to rigidbody.AddRelativeForce

That should add force relative to your coordinate system

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SterlingL · May 27, 2015 at 06:50 PM 0

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This works perfectly. I am working on an Accelerator style game and this worked exactly as I wanted it to in order to allow the camera to lead the direction of my movement. THAN$$anonymous$$S!

Answer 3

Answer by diOriginal · Apr 12, 2013 at 01:39 PM

     if (Mathf.Abs(Input.GetAxisRaw("Vertical")) + Mathf.Abs(Input.GetAxisRaw("Horizontal")) > 0.1f) {
         Vector3 forward = Camera.mainCamera.transform.TransformDirection(Vector3.forward);
         forward.y = 0;
         forward = forward.normalized;
         Vector3 right = new Vector3(forward.z, 0, -forward.x);
         float h = Input.GetAxis("Horizontal");
         float v = Input.GetAxis("Vertical");

         Vector3 moveDirection = (h * right + v * forward);
         moveDirection = Quaternion.Inverse(this.transform.rotation) * moveDirection ;
         moveDirection = new Vector3(moveDirection.x, 0, moveDirection.z); 
         moveDirection = this.transform.rotation * moveDirection;

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Add force relative to camera direction?

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