[Witt3D]

It would be great to have the posibility NOT to render an object in a scene. For example, the emitters. A lot of times it should be great not to see the emitter, but to see the his light.

The same with reflections.

[JTB]

I guess everyone would agree but since this can't happen in reality, maybe you ask this just because other renderers can do this, and not because it would be a real advantage. If there can be such case, I guess the emmiter should be kept out of the view.
What I mean is that there is no invisible light source, right?

[thomas lacroix]

its not because the all renderer is base on accurate physics that we could not have the emitter (not the resultant light thought) to be invisible, its CG afterall and sometimes it could be of advantage not to have them, in real small space for example...