3D Cursor Implementation

[alxdncn]

It would be great to add a 3D cursor that matches the implementation in Unity. This reads from the depth buffer to know where the cursor should be placed on Z, but could also be done with a raycast.

This would ideally also have the 3D orbit controls added, which allow for standard translate, rotate, scale, but also refocus on double-click.

[SinanAkkoyun]

I need help with simply doing mouse raycasting inside the looking glass view, if anyone could help that would be awesome!