2D Top-Down Aiming Using the Mouse in Unity3D

Originally published on my blog: Here

I would like to show you how to make a sprite face the mouse cursor. This is quite useful for aiming in top-down shooters and similar games.

I tried various solutions found on the web, but most of them don't work, work sometimes or work badly. Luckily the easiest solution is also the best one! I found it on YouTube and it is made by Danndx.

The code

Here's the full code:

Vector3 mousePosition = new Vector3 (Camera.main.ScreenToWorldPoint(Input.mousePosition));

Vector2 directionToLookAt = new Vector2(
    mousePosition.x - transform.position.x,
    mousePosition.y - transform.position.y
    );

transform.up = directionToLookAt;

If you are in a hurry you can just copy-paste this code into a script on the object you want to rotate and then call it in the function Update.
But what does this code actually do?

Explaining the code

Vector3 mousePosition = new Vector3 (Camera.main.ScreenToWorldPoint(Input.mousePosition));

Here we get the current mouse position, we translate it into "world coordinates", which are actually usable, and then store it in a Vector3 variable.

Vector2 directionToLookAt = new Vector2(
    mousePosition.x - transform.position.x,
    mousePosition.y - transform.position.y
    );

Create a new Vector2 and store the difference between the mouse position and the object position. We don't actually need the z axis, so we won't use a Vector3 this time.

transform.up = directionToLookAt;

transform.up "Manipulates a GameObject’s position on the Y axis (green axis) of the transform in world space", according to Unity's Docs.
Basically, we rotate the Y axis of the object.

That's all!