Diffuse vs OmniDirectional lighting

Anotrher Thread - Creating recessed strip lighting- had a ceiling lamp which was creating too many individual lights. This was because it was using "diffuse" lighing rather than "omnidirectional" lighting.

The disc at the bottom had three lighting areas - the bottom (red arrow), the top of the disk and the edge of the disk.

They were all marked as diffuse. However, for the edge of the disk, (yellow arrows), this means that we had to create 24 individual diffuse lights - each pointing in a different direction - to send light in 24 different directions. As a result, this single ceiling lamp was creating 26 lights when rendering.

I removed the object properties from all three surfaces of the disc at the bottom, and madeit a group, and marked it as an omni-directional light. Then IRender nXt was able to render it using just one light.

This is an issue on which we are often confused. "Diffuse" lights send out their light in mostly one direction, Omni-directional lights send out their light in all directions. When we create a light from a single face - as in the IRender nXt ceiling lamps - we use diffuse lighting. However, when creating a lighting fixture such as this, your are probably better off with omni-directional lighting.

Here is the lamp with one omni-directional light created from the "group" of the disc.