by Spike » Fri Nov 18, 2011 8:58 am
that's penumbra, which is totally unfeasable with stencil shadows of any form (where the light source is not an infinitely small point, where surfaces can see different amounts of the bulb/filament based upon how obscured it is).
radiosity is light bouncing off surfaces and lighting up other surfaces that are not in line of sight of any part of the light (being able to see the inside/roof of a building despite the sun being outside and above the top of the windows).
.