Jim Holsenback <jho### [at] povrayorg> wrote:
> On 04/01/2011 01:32 PM, Trevor G Quayle wrote:
> >
> > Also I would perhaps call it 'intensity multiplier' or similar.  If you want a
> > base intensity of 2, you would multiply this factor by 2, etc.
> >
> > -tgq
> >
> When you get a second I'd appreciate a little QA:
> http://wiki.povray.org/content/Documentation:Reference_Section_4.4#Light_Fading
>
> Thanks :-)

I think the two paragraphs following the graph need to be expanded somewhat or
the ideas better explained.

A few items:
"First, when Fade_Distance is larger than one, the light intensity at distances
smaller than Fade_Distance actually increases."
Actually this is true for any fade_distance, even when it is smaller than one.

"This is necessary to get the light source color if the distance traveled equals
Fade_Distance."
This isn't really necessary, as the function *could* have been set up the
regular way with 1 instead of 2 in the numerator (as it is for material
attenuation).  I believe it was set up the way it is so that one could set the
fade distance and know that at the fade_distance the light value would equal the
set intensity (a=1).  Meant to somewhat simplify it.

This is the way I had always treated it before until recently.  Now I am seeing
how it doesn't follow a very good inverse-squared relationship over
fade_distance and somwhat beyond if it is used this way.

The way I have come to use it now is to recognize that the function does break
down to be very close to inverse squared as the distance from fade_distance gets
significantly larger.  I think that perhaps this concept should be separated and
explained, as this is the purpose of the example code you have.
If I can find some time in the next few days I will try to consider some wording
for you if you don't come up with something in the meantime.

Also, as proof-reading note, don't use i.e. when you mean e.g.  I.e. means "that
is" and should be used to clarify a general statement that has a specific
meaning, and should not be used in place of e.g. "for example".  In the case
here "i.e.: the size of the light itself" I believe this should be e.g. as it is
one good (and appropriate) example of a value you could choose, but certainly
not the only one.

Sorry if I got a bit too carried away on you, no offense is intended, I have to
review reports for peers at work and for my wife at home, so I tend to get
carried away when doing this.

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