Lerp a vector's rotation ?

Archived Forums Questions & Answers
1

Hello there !

I have a quite simple question to ask. Here’s my problem : I have an object that navigates between random points and I would like it to move smoothly. Put simply : an object reaches its destination and now have a new one. It turns progressively toward its new destination as it moves, defining a curve.
Anyone’s got an idea on how to implement that ?

Thanks in advance for your answer :slight_smile:

Do you want it to be stopped when it's turning or arc towards the point?

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Nope, actually I want it to keep its velocity as it turns.

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What language?

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I use C# for my scripts.

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3 Answers

3
2

If you are trying to lerp rotate only a Vector3, there’s Vector3.Slerp() and Vector3.RotateTowards(). I suggest you look through the Script Reference if you are curious about all the things you can do with a class.

Keep in mind that GameObjects use a class called Transform to describe their orientation in 3D space, so changing a vector might not be what you actually want. Transform’s rotation component is a Quaternion. To spherically interpolate a Quaternion, use Quaternion.Slerp, or any of the other useful functions it has to achieve what you want.

Wow, I could never understand what the Slerp function was for... now I do ! :) Thank you very much for your answer.

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Yeah, Lerp will interpolate on a straight line, like if you were to use a straight edge ruler to draw from one point to another. Slerp will [interpolate on an arc][1], like if you were to use a drafting compass to draw from one point to another. [1]: http://upload.wikimedia.org/wikipedia/commons/b/b3/Slerp_factor_explanation.png

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3

Something like this:

  public float smoothingFactor = 3;
  public Transform target;
  public float speed = 2;
  void Update()
  {
       var directionToTarget = target.position - transform.position;
       //If you are on the ground and only rotating about Y then:
       directionToTarget.y = 0;
       transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookDirection(directionToTarget, Vector3.up), Time.deltaTime * smoothingFactor);
       transform.position += transform.forward * speed;
  }
4

Hey whydoidoit (or anyone really),

What’s the difference between the two rotations below e.g. Quaternion.LookRotation (2 line commented out) vs. Quaternion.Slerp (currently active)

//Move towards new vector position

//this.transform.position = Vector3.MoveTowards(this.transform.position, target, (smoothing * Time.deltaTime));

this.transform.position = Vector3.Lerp(this.transform.position, target, (smoothing * Time.deltaTime));

//Rotate towards new vector position

var dir = target - this.transform.position;

//Example 1 rotation

//var r = Vector3.RotateTowards(this.transform.forward, dir, ((smoothing * 4f) * Time.deltaTime), 0f);

//this.transform.rotation = Quaternion.LookRotation(r);

//Example 2 rotation

transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(dir, Vector3.up), ((smoothing * 4f) * Time.deltaTime));

Thanks for your time and advice in advance!