Rotating my character only while moving in a 2D plane

Questions & Answers
1

Hi everyone. I’ve spent about 6 hours now trying to figure this out… I’ve tried so many different versions of code and nothing seems to work. I’m creating a 2D side scroller and when my character moves I want him to rotate around. Think of sonic the hedgehog when sonic spins and rolls. Or even just think of a sphere that rotates in the direction you move it. I want my character to spin at a very fast rate. I’ve tried adjusting torque and force to my rigidbody over every axis and all that does is make him very choppy; it does not affect his rotation at all. I’m doing something wrong wrong and reaching out in hopes someone might be able to lend a hand. Anyone have any solutions, code snippets or tips using Java?

2

You should use the actual velocity to calculate the rotation, and use transform.Rotate to make it spin. If your character is a rigidbody, you can use:

var factor = 120; // degrees per meter

function FixedUpdate(){
  var angle = rigidbody.velocity.x * Time.deltaTime * factor;
  transform.Rotate(0, 0, angle);
}

This will rotate the character in the direction it’s moving in the X axis (invert angle sign if it spins to the wrong side). You can adjust factor to get the spinning velocity you want.

NOTE: Set rigidbody.freezeRotation=true at Start to avoid interference from physics rotational effects.

EDITED: Well, since you’re using a CharacterController, things must be somewhat different: you must child your model to the character object and rotate it proportionally to the distance travelled each Update (model script):

var speed: float = 120;
private var lastPos: Vector3;

function Update(){
  var dist = transform.position - lastPos;
  lastPos = transform.position;
  var angle = dist.x * speed;
  transform.Rotate(0, 0, angle);
}
3

fyi what aldonaletto wrote works correctly for anyone trying to do this w/ a character controller. Just make sure you adjust the rotate smoothing to 0 and the speed smoothing to a small value (I set it to 0.2) The roll effect works like a charm! :slight_smile: Thanks again!

4

The best solution may be to separate the visual representation from the physics representation. Keep the rigidbody and collider as they are, but have the visible mesh be a component of a child object, then use transform.Rotate on it.