Question by sebkah · May 12, 2019 at 12:32 PM · rotation axis screentoworldpoint aiming

Difficulties using ScreenToWorldPoint to aim

Hi, I'm making a 2D scrolling shooter (but in 3D) and I'm having a hard time making the aiming work. Here's the code sitting on the gun :

         Vector3 mouseWorldPosition = cam.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, cam.farClipPlane));
         mouseWorldPosition.z = 0;       
         transform.LookAt(mouseWorldPosition, Vector3.forward);

I managed to make it behave by fiddling with several nested empty objects to handle the rotation, but it's neither clean or precise.

The problems :

I don't understand precisely the inner workings of ScreenToWorldPoint, especially how it relates to a perspective camera (I'm working in 3D even though it's a 2D scrolling shooter)
- nor did I manage to apply the rotation in a predictable way (only the z rotation must change). Maybe it's just a problem due to how I've organize my objects in the scene (with pivots points and parenting ?)
- The cinemachine camera and its damping messes with the aiming direction (because the player is not centered anymore ?)

Questions :

Shoud I use transform.lookAt() or something like Quaternion.LookRotation()
What is the proper way ?
Do the axis work the same in a 3D project as in a 2D one ?

I found the following way to do it in 2D tutorials but it doesn't seem to translate to 3D coordinates

   Vector3 difference = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, 
     Input.mousePosition.y, 10f)) - transform.position;
     difference.Normalize();
 
     float rotz = Mathf.Atan2(difference.y, difference.x) * Mathf.Rad2Deg;
     transform.rotation = Quaternion.Euler(0f, 0f, rotz);

Thank you for your time and sorry if I'm unclear : I'm a beginner still and my english is rusty ;) !

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