Mr wrote:
> Is there a way to color the highlights of an object in Povray except the metalic
> keyword?

Yes, with a non-white (local, if needed) light source.

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Thorsten Froehlich schrieb:
> Mr wrote:
>> Is there a way to color the highlights of an object in Povray except 
>> the metalic
>> keyword?
> 
> Yes, with a non-white (local, if needed) light source.

That also affects the diffuse color.

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"Mr" <nomail@nomail> wrote:
> Is there a way to color the highlights of an object in Povray except the metalic
> keyword? be it by feeding a simple color vector or a color map? (if some one
> knows blender or max it's the same as putting a single specular color or a ramp
> in the specular texture channel)

Unfortunately not.  For a while I was trying to simulate it with the aoi
pattern, but I couldn't quite get the maths right for making the pattern match
the light.  This is something I wouldn't mind seeing, along with the ambient
keyword accepting a full rgbft vector.


-Reactor

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Reactor schrieb:
> This is something I wouldn't mind seeing, along with the ambient
> keyword accepting a full rgbft vector.

What good would *that* do?

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clipka <ano### [at] anonymousorg> wrote:
> Reactor schrieb:
> > This is something I wouldn't mind seeing, along with the ambient
> > keyword accepting a full rgbft vector.
>
> What good would *that* do?

If you wanted a ghostly object that was only visible when out of direct light,
or a distant moon-like object that has transparent unlit parts, or something
similar.

-Reactor

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Reactor schrieb:
> clipka <ano### [at] anonymousorg> wrote:
>> Reactor schrieb:
>>> This is something I wouldn't mind seeing, along with the ambient
>>> keyword accepting a full rgbft vector.
>> What good would *that* do?
> 
> If you wanted a ghostly object that was only visible when out of direct light,
> or a distant moon-like object that has transparent unlit parts, or something
> similar.
> 
> -Reactor
> 
> 

You mean something like this?

     pigment { color red 0 green 1 blue 0 transmit 0.999 }
     finish { diffuse 0 ambient 1000 }

If that doesn't do what you're thinking of, then a "full rgbtf vector" 
ambient wouldn't help you either.

Also note that the construction you're thinking of would require special 
parsing of the parameter following the "ambient" keyword (or break 
compatibility): As of now, ambient *always* applies filter and transmit, 
but it's taken from the pigment, while what you want would be an 
independent filter and transmit parameter specifically for ambient. As 
from the parser's point of view, "rgb <1,1,1>" is perfectly equal to 
"rgbft <1,1,1,0,0>", this would conflict with the standard use case.

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clipka <ano### [at] anonymousorg> wrote:
> Mr schrieb:
> > Is there a way to color the highlights of an object in Povray except the metalic
> > keyword? be it by feeding a simple color vector or a color map? (if some one
> > knows blender or max it's the same as putting a single specular color or a ramp
> > in the specular texture channel)
>
> A multi-layered texture should to the trick I guess, with the top layer
> defined with the desired highlight color, tramsit 1 and metallic, and
> the lower layer defined without specular highlights.
>
> Didn't test it though.
>
> (Of course this uses the metallic keyword as well, but I reckon your
> question wasn't strictly about avoiding that keyword, but having a
> highlight color different from the diffuse color.)

Yes exactly what I need (I'll have to test it later), and if I want a specular
gradient I can also put other such specular layers with different colors and
roughness/Phong_Size I hope too much of this won't slow down the material too
much, but I guess not since it's only specular, not reflection... I was only
surprised that indenting a color_map under phong or specular wasn't built-in :)
I don't mind such workarounds, they're a really good mind training for me!
You're teaching me a lot these days clipka, thanks. and to the others too very
responsive group. I'll continue stealing your time a little.

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clipka <ano### [at] anonymousorg> wrote:
> You mean something like this?
>
>      pigment { color red 0 green 1 blue 0 transmit 0.999 }
>      finish { diffuse 0 ambient 1000 }

No, and judging from that code sample, I've done a poor job of describing the
effect.

> If that doesn't do what you're thinking of, then a "full rgbtf vector"
> ambient wouldn't help you either.
>
> Also note that the construction you're thinking of would require special
> parsing of the parameter following the "ambient" keyword (or break
> compatibility): As of now, ambient *always* applies filter and transmit,
> but it's taken from the pigment, while what you want would be an
> independent filter and transmit parameter specifically for ambient. As
> from the parser's point of view, "rgb <1,1,1>" is perfectly equal to
> "rgbft <1,1,1,0,0>", this would conflict with the standard use case.

That doesn't sound good, but I made an image that shows more of what I had in
mind.  I posted it in p.b.i here:

http://news.povray.org/povray.binaries.images/thread/%3Cweb.4a7ca1d884f249fd4646012a0@news.povray.org%3E

 The way I understood things, the diffuse keyword controls the texture's amount
of response to light sources.  When checking to see whether or not an object is
lit, the surface normal is checked (to see if the object is facing the light
source).  From my understanding, if we thought of the normal direction as
compared to the light source as returning a percentage of illumination, then
the diffuse would multiplied by that percentage, and the ambient value would be
added (on an rgb component basis).  Assuming this is correct, I was wondering
whether or not the diffuse or ambient component could be full rgb vectors, and
have a filter and transmit value that is taken into account as well.  I'm
probably doing a mediocre job of describing an idea that is based on a poor
understanding of the lighting computations, so hopefully the image will clear
things up.

Anyway, I didn't mean to thread hijack - this started as a well intentioned
gripe about either limitations in controlling the way an object responds to
light, or my limitations in understanding how to control the way an object
responds to light.

-Reactor

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Reactor schrieb:
> That doesn't sound good, but I made an image that shows more of what I had in
> mind.  I posted it in p.b.i here:
> 
>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.4a7ca1d884f249fd4646012a0@news.povray.org%3E

Hum... now, that's a *totally* different thing. And I guess I can 
confirm that indeed it appears to be based on a poor understanding of 
lighting computations ;-)

It would theoretically be possible to *misuse* a transmissive or filter 
component of the ambient to control such an effect, but that's about it. 
The math behind it would have not much similarity with what is done on 
the RGB channels. (And it would pretty much mess up the math, which is 
quirky enough as it is.)

If I were to hard-code anything in POV-Ray to model such an effect, I'd 
go for a kind of "light map" pattern: Taking a #define'd light source 
(or, alternatively, the actual illumination, including radiosity and 
photons and all), possibly multiplying it by some RGB colour, converting 
to greyscale, and using the resulting value to index a pigment or 
texture map. From there, you could easily model precisely the effect you 
want - plus some.

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clipka <ano### [at] anonymousorg> wrote:
> Reactor schrieb:
> > That doesn't sound good, but I made an image that shows more of what I had in
> > mind.  I posted it in p.b.i here:
> >
> >
http://news.povray.org/povray.binaries.images/thread/%3Cweb.4a7ca1d884f249fd4646012a0@news.povray.org%3E
>
> Hum... now, that's a *totally* different thing. And I guess I can
> confirm that indeed it appears to be based on a poor understanding of
> lighting computations ;-)
>
> It would theoretically be possible to *misuse* a transmissive or filter
> component of the ambient to control such an effect, but that's about it.
> The math behind it would have not much similarity with what is done on
> the RGB channels. (And it would pretty much mess up the math, which is
> quirky enough as it is.)
>
> If I were to hard-code anything in POV-Ray to model such an effect, I'd
> go for a kind of "light map" pattern: Taking a #define'd light source
> (or, alternatively, the actual illumination, including radiosity and
> photons and all), possibly multiplying it by some RGB colour, converting
> to greyscale, and using the resulting value to index a pigment or
> texture map. From there, you could easily model precisely the effect you
> want - plus some.


I think I just might have to start a new feature request thread, then.  That
description suddenly reminded me of the projection pattern in MegaPov, so I'm
going to go try abusing that some more first.  First experiments look sort of
promising.

-Reactor

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