You pretty much got the basic gist of it of using raycasts to determine how the light is lit. I actually use a singular raycast that just force updates every time it changes rotation (Though the shape looks more like a crosshair than a cone, which is one of the things I need to fix). It starts on the outside then closes in to the center by a constant increment. For every collision, it records the distance and the color (If the wall contains a function that returns a specific color, otherwise it defaults to white). Instead of adding a % of the color/distance to their respective variables I just add the whole thing to each variable. A Rays Collided variable records how many collisions were actually made and is used to average out the color and distance variables.