Hi, I'm having trouble with a player controller I'm developing. Basically, there are many small planetoids... the player can run around on these planets (so gravity is always a force that is planet.position - player.position)

(Unity C#)

I can move the player around the planet just fine, and the player's up vector always faces opposite gravity direction, but I can't seem to rotate the player towards horizontal input axis if the gravity is anything other than -y.

ie, if I change gravity like I am, planet.pos - player.pos, i can't seem to simultaneously affect both the up vector of the player and a rotation around that up vector

It appears I don't know how to affect a single quaternion axis... for example, I'd love to do something like...

rotate.yAxis(horizontal input * rotation speed) while local upVector = -gravityDirection

but unfortunately that's only pseudo code : (

here is code that's getting me close

void FixedUpdate()
    {
        _rigidbody.MovePosition(_rigidbody.position + transform.TransformDirection(moveDirection) * moveSpeed * Time.deltaTime);

        gravityDirection = (_planetoid.transform.position - transform.position).normalized;
        _rigidbody.AddForce (gravityDirection * gravityStrength);

        gravityRotation = Quaternion.FromToRotation (Vector3.up, -gravityDirection);

        OnTurn(gravityRotation);
    }

    void OnTurn(Quaternion rot)
    {
        targetRotation *= Quaternion.AngleAxis(rotationVelocity * h * Time.deltaTime, transform.up);
        transform.rotation = rot; // ******** swap this out for targetRotation ***********
    }

// ******** swap this out for targetRotation ***********

this is saying that if rot is the variable being used, the player runs around the player properly (always appearing to be standing upright no matter where they are on the planet), but rotating towards input doesn't work.

if you swap rot out for targetRotation, the player rotates towards input axis, but no longer aligns to the planets surface

any help would be amazing

What do you mean by horizontal input axis? And can you provide a video of the problem?

EDIT: I should also note that gravity does not cause rotation it's self. So there is little need to have rotation be modeled by physical math.

Test to see what Celestial body has the greatest pull on the object in question. If the force is strong enough to pull the object into it's own surface, then change the direction to the new Celestial body.

transform.rotation = Quaternion.LookRotation(_planetoid.transform.position - transform.position).normalized)

This hasn't been tested myself, and I am not too familiar with Unity's API. But conceptually it should work. Hopefully anyways.

Also character rotation from player input will need to be modified as well. Easiest way to do that, is to treat the character as if he was always standing up straight. Rotate him. Then apply the look at transformation. That is assuming that Unity does it's best to keep a frame of reference when it does a look at.

I hope this video can illustrate my issue better

thanks for the help guys

*edit* @tangletail - more specifically, horizontal input axis is a value from -1 to 1, depending on how far a joystick is moved

@happycoder, does your suggestion only work when the player is perpendicular to the camera?