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From: Christophe Bouffartigue
Subject: Re: metal without ambient and r2d2
Date: 20 Jul 2000 07:11:47
Message: <3976DE74.53270220@nanterre.marelli.fr>
ryan constantine wrote:
> 
...
> examination of the metals available in both pov and moray, i found that
> all of them had an ambient value.  so the question is how does one make
> metal without it?

If you want no ambient light in all the scene, just use ambient_light
0.0 in your global_settings statement.

Bouf.


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From: Bob Hughes
Subject: Re: metal without ambient and r2d2
Date: 20 Jul 2000 10:53:29
Message: <39771269@news.povray.org>
"ryan constantine" <rco### [at] yahoocom> wrote in message
news:3976BA97.A450157C@yahoo.com...
| because it was recommended in the docs (3.1 or mega, i can't recall
| which) that when using radiosity one should not have ambient objects.
|  so the question is how does one make metal without it?

I've used something like ambient_light 0.2 along with assumed_gamma 3 so
that I don't lose all aspects of the original ambience.  Trick is to keep
the ambient very low when doing MegaPov radiosity.  Either that or you might
have to raise all the diffuse values.  I'm sure it's been asked before about
how it might benefit to have a global diffuse also, and with this "new"
radiosity I think it is needed more than ever.  Not that I know if that
would be appropriate to do.

Bob


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From: ryan constantine
Subject: Re: metal without ambient and r2d2
Date: 20 Jul 2000 18:20:59
Message: <39777B0D.CF2DB5E9@yahoo.com>
> :  in a cursory
> : examination of the metals available in both pov and moray, i found that
> : all of them had an ambient value.  so the question is how does one make
> : metal without it?
> 
>   Just removing the ambient value perhaps?
 of course i tried that, but (naturally) they get really dark.  so i
guess more precisely i want to know how to compensate for the darkness.


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From: ryan constantine
Subject: Re: metal without ambient and r2d2
Date: 20 Jul 2000 18:22:40
Message: <39777B72.7281C94@yahoo.com>
does this effectively eliminate all ambient items in textures?  or does
it do something else?  and if it does eliminate the ambient parts of
textures, the textures will be darker, so how do i conpensate?  or
should radiosity compensate for me?

Christophe Bouffartigue wrote:
> 
> ryan constantine wrote:
> >
> ...
> > examination of the metals available in both pov and moray, i found that
> > all of them had an ambient value.  so the question is how does one make
> > metal without it?
> 
> If you want no ambient light in all the scene, just use ambient_light
> 0.0 in your global_settings statement.
> 
> Bouf.


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From: Tom Melly
Subject: Re: metal without ambient and r2d2
Date: 21 Jul 2000 04:25:04
Message: <397808e0$1@news.povray.org>
"ryan constantine" <rco### [at] yahoocom> wrote in message
news:397### [at] yahoocom...
> does this effectively eliminate all ambient items in textures?  or does
> it do something else?  and if it does eliminate the ambient parts of
> textures, the textures will be darker, so how do i conpensate?  or
> should radiosity compensate for me?

the global ambient acts as a multiplyer for local ambients, so setting it to
0 will eliminate all ambients (the default is presumably 1).

Radiosity should compensate - essentially, ambient is faked radiosity
(IMHO).


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From: Christophe Bouffartigue
Subject: Re: metal without ambient and r2d2
Date: 21 Jul 2000 04:33:25
Message: <39780AD4.1759784F@nanterre.marelli.fr>
ryan constantine wrote:
> 
> does this effectively eliminate all ambient items in textures?  or does
> it do something else?  and if it does eliminate the ambient parts of
> textures, the textures will be darker, so how do i conpensate?  or
> should radiosity compensate for me?

It modify all the ambient in all textures like this:

final_ambient = finish_ambient * ambient_light.

When using radiosity, I generally use ambient_light 0.2 or 0.3 to lower
the impact of ambient light (which is a *very* rough and inaccurate form
of radiosity...).


Bouf.


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From: Kari Kivisalo
Subject: Re: metal without ambient and r2d2
Date: 21 Jul 2000 14:32:45
Message: <39789750.4C9C6D3C@kivisalo.net>
Use assumed_gamma 1.0 and whatever is correct Display_Gamma
for your system in povray.ini. When removing the static ambient
light it is important to set gamma correctly so that radiosity
can produce correct ambient level. See
news://news.povray.org/39423CFE.5565DBF%40kivisalo.net
news://news.povray.org/39450341.610E8FC3%40kivisalo.net


K.K.


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From: ryan constantine
Subject: Re: metal without ambient and r2d2
Date: 21 Jul 2000 15:45:19
Message: <3978A814.307CA5AD@yahoo.com>
thanks for the tips.  is there a default assumed_gamma?  the reason i
ask is because in moray, the assumed_gamma box actually outputs the same
number for both the display_gamma setting in the ini file and the
assumed_gamma in the pov file.  i'm not sure how to fix this.  of
course, i could always just open the exported file in megapov itself and
this is what i'll do if there is no way of dealing with it in moray
itself.  thanks again. 

Kari Kivisalo wrote:
> 
> Use assumed_gamma 1.0 and whatever is correct Display_Gamma
> for your system in povray.ini. When removing the static ambient
> light it is important to set gamma correctly so that radiosity
> can produce correct ambient level. See
> news://news.povray.org/39423CFE.5565DBF%40kivisalo.net
> news://news.povray.org/39450341.610E8FC3%40kivisalo.net
> 
> K.K.


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From: Zeger Knaepen
Subject: Re: metal without ambient and r2d2
Date: 23 Jul 2000 09:00:01
Message: <397aec51@news.povray.org>
When making a metallic texture, I *always* use ambient 0:
pigment {rgb <.95,.975,1>}
finish {ambient 0 diffuse .7 brilliance 10 reflection .2 reflect_metallic
specular 1 roughness .01 metallic}
But I don't think it would make a good metal for R2D2's head.  This might be
better:
finish {ambient 0 diffuse .8 brilliance 3 reflection .05 reflect_metallic
specular 1 roughness .01 metallic}

(I haven't tested them)

ZK
http://www.povplace.be.tf


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From: ryan constantine
Subject: Re: metal without ambient and r2d2
Date: 23 Jul 2000 17:50:09
Message: <397B685D.CAD64552@yahoo.com>
that was helpful.  thanks.  now check out my new post in this group.

Zeger Knaepen wrote:
> 
> When making a metallic texture, I *always* use ambient 0:
> pigment {rgb <.95,.975,1>}
> finish {ambient 0 diffuse .7 brilliance 10 reflection .2 reflect_metallic
> specular 1 roughness .01 metallic}
> But I don't think it would make a good metal for R2D2's head.  This might be
> better:
> finish {ambient 0 diffuse .8 brilliance 3 reflection .05 reflect_metallic
> specular 1 roughness .01 metallic}
> 
> (I haven't tested them)
> 
> ZK
> http://www.povplace.be.tf


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