Question How do I make a 2d tilemap cast shadows?

I have a procedurally generated tilemap that can be changed by the player, like terraria, and I want to have it cast shadows. I think a way of doing it is by generating a shadow caster around the player based on the composite of the tilemap.

 

The only way I can think of doing this is by making a script that creates a shadow caster for each tile around the player, but that causes way too many crashes.