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"Kenneth" <kdw### [at] earthlink net> wrote:
>>Likewise, using rgbf <1,0,0,.5> would cast a reddish,
> variable-density shadow.
>
Actually, using rgbft is better; varying f and t produces any shade or
density of shadow.
SO... after *finally* getting around to rendering my "two identical objects"
experiment using an area light, I discovered something interesting: The
order of the two objects in the scene file -- which one comes first --
becomes important. My original test used just a single point light, to
prove the concept; and the order didn't matter. But with an area light,
the order DOES matter. The no_image sphere--the one casting the
shadow--has to come first in the code, otherwise NO shadow is produced.
I'll leave it up to more brilliant minds than mine to figure out why that
is so. :-) But the trick works quite well, even using rgbft as above, with
no shadow problems that I can see.
Ken
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Kenneth nous apporta ses lumieres en ce 29-01-2007 04:46:
> "Kenneth" <kdw### [at] earthlinknet> wrote:
>> ...in
>> experiments I've done, using two simple spheres (one with no_shadow, one
>> with no_image) and a single point light just for simplicity, what I see is
>> that the final shadow, cast onto a white ground plane, is still quite dark.
>> *Almost* black...
> I took a more critical look at my own test image, and I have to conclude
> that the final shadow isn't "almost black," it IS black. The shadow (from
> the no_image sphere) is somehow taking complete precedence. There's no
> "brightness mixing" at all. Odd, but interesting. Perhaps that's just the
> logical operation of POV's shadow calculations.
> Meanwhile, my little test has presented another useful trick, something I've
> been pondering for awhile but couldn't figure out how to do, until now:
> creating a variable-density shadow. By making the pigment of the no_image
> sphere something like rgbt <1,0,0,.5> (the rgb components don't really
> matter), its shadow can be made more or less dense/dark. So that an object
> that appears to be solid (the no_shadow sphere, in my case) can cast a
> variable-darkness shadow. May not be physically realistic, but could be a
> useful artistic tool. Likewise, using rgbf <1,0,0,.5> would cast a reddish,
> variable-density shadow.
> Ken
Are you using light_group? In that case, if the no_shadow object is in a group
with a given light source, that light will only illuminate that object, unless I
missunderstood the working of a light_group.
--
Alain
-------------------------------------------------
Don't try so hard, the best things come when you least expect them to.
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Alain <ele### [at] netscapenet> wrote:
> Are you using light_group? In that case, if the no_shadow object is in a group
> with a given light source, that light will only illuminate that object, unless I
> missunderstood the working of a light_group.
>
Nope, no light_group. But I think your understanding is correct.
You're question gives me some more thoughts. I'll try these tricks with a
light_group, to see if anything odd or interesting pops up.
KW
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