How to set single axis of rotation?

I think the solution to this is probably simple but I'm new at this.

I'm making an endless driving/shooting game. I have a car with a turret on the roof. The turret is a child of the car. I'm trying to write some code to control the rotation of the turret using the right joystick. I only want to set the y-axis. I want the turret to inherit the x and z rotation from the car.

My camera is locked pointing toward z. So in terms of setting the y rotation, it could be relative to the camera or the world space. I think it would be the same in this case. 0 degrees is forward, 90 degrees is right, etc...

Here some temporary code I was using to control the turret. It's ok on flat terrain but it overrides the x and the z rotation as well so when the car rides on slopes the turret remains level, clipping into the roof of the car.

Code (CSharp):

1.         Vector3 lookDirection = new Vector3(Input.GetAxisRaw("R_Horizontal"), 0, Input.GetAxisRaw("R_Vertical"));
2.         Turret.rotation = Quaternion.LookRotation(lookDirection);

What's the right way to do this?

 

You could project the look direction onto the desired plane before using it as the look rotation. Also LookRotation has a second parameter specifying the "up" direction, which seems relevant here. Otherwise it uses world up (Vector3.up) which will make it off-kilter from the parent.

Code (CSharp):

1.         Vector3 lookDirection = new Vector3(Input.GetAxisRaw("R_Horizontal"), 0, Input.GetAxisRaw("R_Vertical"));
2.         Vector3 projectedLookDirection = Vector3.ProjectOnPlane(lookDirection, Turret.parent.up);
3.         Turret.rotation = Quaternion.LookRotation(projectedLookDirection, Turret.parent.up);

 

That did it. Thank you.