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Mike Thorn wrote:

| First of all, a default light source has no falloff. The light rays
will
| be equally bright whether they're 100 units away or 10,000 units. The
| only difference is how many rays hit the object (since a default light
| source emits light in all directions, placing the light source very
far
| away spreads the rays out more, thereby making an object *appear*
| darker). In reality, it's just receiving fewer beams.
|
	There appears to be a small misunderstanding on how light sources
work here. For regular light sources (ie not area lights), there is
exactly one ray of light for each point of your object no matter what
the distance to the light source. If you don't use anything special
like falloff or semi-transparent objects, that light ray will have
the exact intensity specified in the light source definition. As a
result, the object will have about the same brightness no matter how
far the light source is situated. However the brightness is affected
by the angle between the light ray and the surface: it is maximal if
the ray hits the surface straight on and diminishes to zero when the
ray is nearly parallel to the surface. This is why placing the light
source farther away makes for more uniform illumination: the farther
away, the closer to parallel the rays.

	Incidentally, your description ("rays spread out more") is more or
less what happens in real life and the reason why real light sources
get dimmer with distance.

| There are ways to make the light sources behave realistically. POV-Ray
| supports light falloff and fading, which, when set properly (an area I
| can't advise on, unfortunately) can produce quite realistic
results. If
| you want to look these up, look for the 'falloff' and 'fade_distance'
| keywords in the Help file.
|
	To get realistic results, you should use "fade_power 2" and set the
fade_distance to the size of your light bulb, then give a *very* high
value for light intensity (you do know that intensity is not
constrained to the 0-1 range, don't you? In fact you can even create
negative light sources wich allows for some interresting special
effects...). 'falloff' has nothing to do with it and has meaning only
with spotlights and cylindrical lights: it defines how much light you
get as you get further from the center of the beam.

	BTW, if you intend to use cylindrical lights, read the doc
carefully, they probably don't do what you think. To get the right
effect, you'll have to look at the 'parallel' keyword :p

		Jerome

- --
******************************
*      Jerome M. Berger      *
* mailto:jbe### [at] ifrancecom *
*  http://jeberger.free.fr/  *
******************************
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