On 12/5/2016 12:33 PM, omniverse wrote:
> So this means the current way radiosity works is only to brighten upward from a
> certain threshold (the actual pigment color, or lack of any) and never go lower?


You could try negative light for darkening.

-- 

Regards
     Stephen

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Am 05.12.2016 um 13:33 schrieb omniverse:

> Sounds like I was under the wrong impression, thinking already dark areas would
> get darker still. I just figured that would be how it would be, as though
> illumination drops. Ultimately to zero. I had thought in terms of a light fade
> for radiosity, of sorts. Like a shadow + dark color = darker shadow, or
> something along those lines of thinking.
> 
> So this means the current way radiosity works is only to brighten upward from a
> certain threshold (the actual pigment color, or lack of any) and never go lower?

The lower threshold is actually the direct brightness from conventional
light sources. In full shadow, that would be zero.

But normally there's barely a crevice where radiosity-based illumination
doesn't find a way in.

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clipka <ano### [at] anonymousorg> wrote:
> Am 05.12.2016 um 13:33 schrieb omniverse:
>
> > Sounds like I was under the wrong impression, thinking already dark areas would
> > get darker still.
> >
> > So this means the current way radiosity works is only to brighten upward from a
> > certain threshold (the actual pigment color, or lack of any) and never go lower?
>
> The lower threshold is actually the direct brightness from conventional
> light sources. In full shadow, that would be zero.
>
> But normally there's barely a crevice where radiosity-based illumination
> doesn't find a way in.

Okay. Wrapping my head around this, I believe. I had been thinking in terms of a
dual effect, namely illumination and anti-illumination.

And as Stephen suggested, negative light color doesn't seem to adversely affect
radiosity, as in uncontrollable way, so maybe there are possibilities with that.

This had me trying negative emission and I was surprised by the result, although
perhaps I shouldn't be based on what you've been saying.

A test of 2 spheres, rgb 1 and rgb 0 both with emission -1, caused only a
darkened area for the white (now black) sphere on a white plane.
Black sphere with emission -1 made no change to the white plane below it.

I take from this that color > 0 is required for emission to do anything. This in
turn makes me think there should be some way to get a black or dark object to
enhance the darkness around it.

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On 12/5/2016 4:14 PM, omniverse wrote:
> And as Stephen suggested, negative light color doesn't seem to adversely affect
> radiosity, as in uncontrollable way, so maybe there are possibilities with that.

You can use a non reflecting diffuse thin box as a fill in like they do 
in photography. If you make its colour negative it sucks the light out. 
Or so it seemed to me when I tried it.

-- 

Regards
     Stephen

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Am 05.12.2016 um 17:14 schrieb omniverse:

> A test of 2 spheres, rgb 1 and rgb 0 both with emission -1, caused only a
> darkened area for the white (now black) sphere on a white plane.
> Black sphere with emission -1 made no change to the white plane below it.
> 
> I take from this that color > 0 is required for emission to do anything. This in
> turn makes me think there should be some way to get a black or dark object to
> enhance the darkness around it.

Try positive emission with a negative pigment ;)

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clipka <ano### [at] anonymousorg> wrote:


> > I take from this that color > 0 is required for emission to do anything.

I'd predict that based on 0 * -1 = 0.

> This in
> > turn makes me think there should be some way to get a black or dark object to
> > enhance the darkness around it.

Have it run for public office.  ;)  :D

> Try positive emission with a negative pigment ;)

:O  You'll blow something up for sure!

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clipka <ano### [at] anonymousorg> wrote:
> Am 05.12.2016 um 17:14 schrieb omniverse:
>
> > A test of 2 spheres, rgb 1 and rgb 0 both with emission -1, caused only a
> > darkened area for the white (now black) sphere on a white plane.
> > Black sphere with emission -1 made no change to the white plane below it.
> >
> > I take from this that color > 0 is required for emission to do anything. This in
> > turn makes me think there should be some way to get a black or dark object to
> > enhance the darkness around it.
>
> Try positive emission with a negative pigment ;)

Except that wouldn't allow for a dark, yet positive value, color to likewise
darken its surroundings.

Of course, the more I think it over I don't know how much this would be
deviating from real world. Something I haven't checked into.

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"Bald Eagle" <cre### [at] netscapenet> wrote:
> clipka <ano### [at] anonymousorg> wrote:
>
>
> > > I take from this that color > 0 is required for emission to do anything.
>
> I'd predict that based on 0 * -1 = 0.
>
> > This in
> > > turn makes me think there should be some way to get a black or dark object to
> > > enhance the darkness around it.
>
> Have it run for public office.  ;)  :D
>
> > Try positive emission with a negative pigment ;)
>
> :O  You'll blow something up for sure!

LOL Heck, I haven't had anything to do with politics since turning 18 years old
a few days before a presidential election. The only time (almost) I was ever
compelled to vote.

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Am 05.12.2016 um 19:43 schrieb omniverse:
> clipka <ano### [at] anonymousorg> wrote:
>> Am 05.12.2016 um 17:14 schrieb omniverse:
>>
>>> A test of 2 spheres, rgb 1 and rgb 0 both with emission -1, caused only a
>>> darkened area for the white (now black) sphere on a white plane.
>>> Black sphere with emission -1 made no change to the white plane below it.
>>>
>>> I take from this that color > 0 is required for emission to do anything. This in
>>> turn makes me think there should be some way to get a black or dark object to
>>> enhance the darkness around it.
>>
>> Try positive emission with a negative pigment ;)
> 
> Except that wouldn't allow for a dark, yet positive value, color to likewise
> darken its surroundings.

If that's what you absolutely positively need, there's always the option
to hide your proper object from radiosity using "no_radiosity", and
setting up a menacingly dark radiosity stunt double using "no_image
no_reflection no_shadow".


> Of course, the more I think it over I don't know how much this would be
> deviating from real world. Something I haven't checked into.

Emit darkness? Why, yes - I guess that may need /some/ degree of
deviating from real world :P

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clipka <ano### [at] anonymousorg> wrote:
> Am 05.12.2016 um 19:43 schrieb omniverse:
> > clipka <ano### [at] anonymousorg> wrote:
> >> Try positive emission with a negative pigment ;)
> >
> > Except that wouldn't allow for a dark, yet positive value, color to likewise
> > darken its surroundings.
>
> If that's what you absolutely positively need, there's always the option
> to hide your proper object from radiosity using "no_radiosity", and
> setting up a menacingly dark radiosity stunt double using "no_image
> no_reflection no_shadow".
>
>
> > Of course, the more I think it over I don't know how much this would be
> > deviating from real world. Something I haven't checked into.
>
> Emit darkness? Why, yes - I guess that may need /some/ degree of
> deviating from real world :P

heh-heh-heh! Mmmm. Perhaps, perhaps. Did think about a stunt double thing,
although I would probably be the one doing the stunts trying to get that right.

Bob

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