Problem, local lights not lighting some surfaces.

I've been working on a building and have recently added some lanterns with a local light source around them. The light source does light up my AV when it is near or under it, but does not appear to be lighting the walls of the building. Outside the building the land has snow, which is receiving light form the light source thru the walls.

Why would my lights be lighting everything, including ground outside the building, except the building itself?

Local light behaves in some funny ways. First, the light radius is determined by the size of the prim casting the light. I'm not sure of the exact figures, but a 10M prim will cast light further away from itself than will a 1M prim. One 10M prim has more "candle power" than do ten 1M prims.

Second, as you noticed, prims do not block light. The light goes right through them to illuminate objects or land behind them, as if they weren't even there.

Third, generally prims will be lit only if the local light hits their centerpoint. So, it's not uncommon to end up seeing the individual rectangular components of a large wall, for example, as those prims with centers inside the light radius get locally lit and those with centers outside do not.

On very rare occasions, I've seen local light seem to behave as it should, casting light in a graduated spherical pattern, but each time the effect has been short lived, only lasting a second or two before snapping back to whole prim lit/whole prim unlit mode. I don't know what those brief periods of semi-realistic light behavior have meant from a technical standpoint, but they've sure looked nice while they've lasted. Too bad they're not the norm.

Thanks for the explanation. I did discover last night a big part of my problem was this huge light source on the land next to where I’m building. It was just a big invisible rectangle with light property set and no other object was on the land. Also two different people owned the object and the land. This huge light source was washing out the effects of my much smaller lights. I’ve asked for it to be removed. We’ll see what happens.