How to make a Selection Box?

I’m creating a transparent box that will serve as a “selection box” for other objects. My idea is to just put the main object inside this box, I don’t know if it’s the best approach, if you have any better ideas let me know.

In the image below I’m just using a cube with an unlit material.

There are some points that I don’t know how to resolve:

  • I want the material to be emissive, but not illuminate surrounding objects.
  • It should also not cast shadows.
  • The texture cannot be distorted when scaling the box.

Any suggestions?