William F Pokorny <ano### [at] anonymousorg> wrote:
>
> I dug up the source code not too long ago and made these notes:

Fascinating! Thanks for taking the time to do this, and for posting your info.
>
> ---
> C seems to stand for color. (There are other unused classifications)
> The number after the D is depth. I've only ever seen 1 or 2 - maybe if
> recursion depth increased?

Yes, you're right, it's recursion_limit. (In my tests so far, I had set it to
2.) I ran another test with somewhat high-quailty settings (to produce a LARGE
saved rad file), and cranked resursion_limit up to 20. Now I see data lines
starting with C3,C4 etc. Interestingly, they 'top out' at about C8-- with fewer
entries too-- which agrees with the documentation about higher recursion_limit
settings having less and less of a visual effect on the render.
>
> The next three float values are the location...
> ...
>
> In field 10 the nearest sample distance found is recorded.
>
> Field 11, like the normal field, is a string representing 3 x,y,z values
> pointing, roughly in the direction where the nearest distance sample was
> taken.

From my animation tests with a moving camera, I assume that the x,y,z
values/direction vectors have something to do with CAMERA's viewpoint as well
(whatever it happens to be.) That is, if I understand your description
correctly.
>
>
> Aside: I suspect, there are some similarities to the saved photons file,
> but I've not gotten to even a first look at it...
>

IMO, there does seem to be a similarity:

I did an odd radiosity test, using a sky dome photo for the rad emitter, a gray
ground plane, and a perfectly-relective sphere for a scene object...
    (ambient 0 emission 0 diffuse 0 reflection 1.0)
... except that I cranked up its reflection to 8.0-- just an arbitrarily HIGH
value. I also added a normal to it. The result is that the sphere actually
reflects the incoming radiosity light.. and produces crude 'radiosity caustics'
on the plane, no photons required! I didn't realize that radiosity light could
be reflected, without using photons in some way. It seems that the two methods
do operate in a somewhat similar(?) way.

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