Hide a really bright light inside the box when you shoot. The really tough part of the effect is then done. Adding a volumetric glow can be done in a couple-three different ways.
There are some plug-ins that will stimulate this. You also need to learn about blend modes.
- Create a triangular like blue shape layer on top of your footage
- Add fast a blur or gaussian blur of about 150 pixels
- Change the blending mode to add
- Adjust the opacity
There is the basic theory. Depending on your saying you may need to use rotoscoping two separate foreground, middle ground, and background elements in the scene and layer the light effects between the layers. If there is movement in the camera then you will probably need to stabilize motion or track motion to get this to work.
They will also need to add some smoke or dust for the light in the box to have an atmospheric sense.