beams of light through open doors?

[UltraProAnti]

Remember in Ravenholm when you first see Father Grigory - he's standing in a doorway above and in front of you with a volumetric lightbeam shining out from behind him.

Now, I know how to make a spotlight. But does anyone know if the beam in Ravenholm is square, or does the doorframe provide the occlusion necessary to make it look square (i.e. does the beam act like a real beam, or is it a entity parameter I'm unaware of that makes it square/rectangular/whatever)?