Hi,

let's assume a cave (an isosurface) illuminated with hundreds of candles close
to the wall of the cave.
Each candle gets its light_source with a certain fade_distance and fade_power in
order to attain a nice illumination, so each candle only illuminates the cave
wall very close to the candle.

Now we have the problem that rendering goes very slowly, since each point of the
isosurface has to consider each light_source. On the other hand, the result
would look much the same, if each point of the cave wall considers only the 1, 2
or 3 nearest candles (due to the small fade_distance and rather high fade_power
candles more far away won't take any effect on the brightness of this location).

A work-around would be to split the cave into many intersections, each combined
with one candle in a light_group. This, however, would not be a smart solution
(and I'm not sure if it really works).

So what about introducing a "max_distance" keyword to a light_source?

This means, each point of a scene only considers light_sources which a closer
than "max_distance". The default value, of course, would be infinity (maybe
represented by a negative value, or a zero).

I have lots of scenes which would benefit from such a (as I think very easy to
implement) keyword by means of rendering speed.

To be honest, I wonder why such a keyword has not been introduced up to now - or
have I overseen it?

Kind Regards!

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