Top down 2D lighting: How can colour/shade areas of my map?

[rapidbuster]

I am working on a top-down 2D game. I would like to end up with something like this:

I can figure out the raycasting and the geometry bits. At which point I will have a set of polygons that I want to be light, and I want the rest of the map to be dark.

I do not know how to achieve this effect in unity, however. I am considering trying to apply an alpha mask to the camera such that it will only show the white polygons. I could then use Texture2D.SetPixels to update the alpha map.

Does anybody know if this is possible, or if there is an easier way to achieve the same effect?

Thankyou kindly.

[Cherno]

Since your camera appears to be orthographic, you could just apply a material using an unlit shader with a white color/texture to the visible/light mesh, and a black one to the others (or just not renderer the “real” geometry at all, and only have a black background with the white mesh showing the visible parts rendered on top). I don’t know how resource-intensive it would be to reassign vertices of a mesh every frame, though.