What's it all about?
Photometric data for a real fixture
Real lights distribute their light energy asymmetrically. They aren't points, nor are they cones. The simplified and abstracted lighting possible with such lights is suitable for many modeling situations, but not all. Sometimes you really want to know "what it looks like".
Answering the question in a reliable, verifiable way involves simulating the lighting, not just rendering. That means algorithmic differences (see the discussion of radiosity), but these aren't enough all by themselves. We also need a "richer" representation of the light source itself.>
Last updated: April, 2014