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I do like a wee dram but I noticed that when I turned on photons the
whisky colour of the shadow went. I have posted an almost minimal
scene below in p.g. It was modelled in Moray for those of you that
don't recognise the coordinate system.
The leftmost glass has photons {pass_through} to simulate not using
photons.
Any help appreciated.
Regards
Stephen
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Attachments:
Download 'a02a_1xb2.png' (54 KB)
Preview of image 'a02a_1xb2.png'
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From: Slime
Subject: Re: Loss of colour in shadow when using photons. - a02a_1xb2.png
Date: 12 Nov 2004 14:39:34
Message: <41951176$1@news.povray.org>
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> I do like a wee dram but I noticed that when I turned on photons the
> whisky colour of the shadow went.
This is physically correct. Any light passing through the glass becomes a
photon. Notice that the photon-covered areas *are* colored, since that light
is filtered by the color of the drink. The rest of the shadow is uncolored
because none of the light hitting that area has passed through the glass.
In fact, the only reason the unlit area of the shadow isn't completely black
is probably because of "ambient" light, which has a constant value
everywhere (unless you use radiosity).
- Slime
[ http://www.slimeland.com/ ]
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On Fri, 12 Nov 2004 14:39:32 -0500, "Slime" <fak### [at] email address>
wrote:
>
>In fact, the only reason the unlit area of the shadow isn't completely black
>is probably because of "ambient" light, which has a constant value
>everywhere (unless you use radiosity).
Blow me down! You're right. What sort of photon settings would I have
to use to get a coloured shadow? I think as many as there are in RL,
gulp! The photons are there to get the caustics from the cut glass
(missed out in this rendering) I suppose I can live with it. Thanks a
lot.
Regards
Stephen
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From: Slime
Subject: Re: Loss of colour in shadow when using photons. - a02a_1xb2.png
Date: 12 Nov 2004 15:24:07
Message: <41951be7$1@news.povray.org>
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> Blow me down! You're right. What sort of photon settings would I have
> to use to get a coloured shadow? I think as many as there are in RL,
> gulp!
It looks to me like you have as many photons as you need; adding more
photons will only increase the resolution of the bright spots, it won't
brighten the dark areas at all.
If it looks different in real life, then maybe you have your ior set
incorrectly (too high?) or maybe it's due to scattering of the light within
the liquid, which could possibly be simulated by adding a small-scaled
normal to the liquid's surface.
- Slime
[ http://www.slimeland.com/ ]
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On Fri, 12 Nov 2004 15:23:55 -0500, "Slime" <fak### [at] emailaddress>
wrote:
>If it looks different in real life, then maybe you have your ior set
>incorrectly (too high?) or maybe it's due to scattering of the light within
>the liquid, which could possibly be simulated by adding a small-scaled
>normal to the liquid's surface.
Hmm, ior was set too low for both liquid and glass. The liquid is a
solid :-) so I'll try a ripple noise pattern wank up the photons for
caustics and let it run overnight.
The thing is I've drank all my whisky and I can't view it in RL.
Thanks for your help.
Regards
Stephen
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mca### [at] aolcom news:8g9ap0p5b48db4qi39789e7h4dvfbr9sek@4ax.com
> Hmm, ior was set too low for both liquid and glass. The liquid is a
> solid :-) so I'll try a ripple noise pattern wank up the photons for
> caustics and let it run overnight.
Also YOu might
1) turn on radiosity
2) add scattering media to water and set media on in radiosity{}
--
http://www.raf256.com/3d/
Rafal Maj 'Raf256', home page - http://www.raf256.com/me/
Computer Graphics
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From: Andy Cocker
Subject: Re: Loss of colour in shadow when using photons. - a02a_1xb2.png
Date: 12 Nov 2004 16:21:04
Message: <41952940@news.povray.org>
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"Stephen McAvoy" <mca### [at] aolcom> wrote in message
news:8g9ap0p5b48db4qi39789e7h4dvfbr9sek@4ax.com...
> On Fri, 12 Nov 2004 15:23:55 -0500, "Slime" <fak### [at] emailaddress>
> wrote:
>....wank up the photons ....
<snigger>
Andy Cocker
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From: Ross
Subject: Re: Loss of colour in shadow when using photons. - a02a_1xb2.png
Date: 12 Nov 2004 16:40:46
Message: <41952dde$1@news.povray.org>
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"Rafal 'Raf256' Maj" <spa### [at] raf256com> wrote in message
news:Xns959FE37EC56A3raf256com@203.29.75.35...
> mca### [at] aolcom news:8g9ap0p5b48db4qi39789e7h4dvfbr9sek@4ax.com
>
> > Hmm, ior was set too low for both liquid and glass. The liquid is a
> > solid :-) so I'll try a ripple noise pattern wank up the photons for
> > caustics and let it run overnight.
>
> Also YOu might
> 1) turn on radiosity
> 2) add scattering media to water and set media on in radiosity{}
>
> --
3) buy more whiskey.
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From: Nathan Kopp
Subject: Re: Loss of colour in shadow when using photons. - a02a_1xb2.png
Date: 12 Nov 2004 23:36:28
Message: <41958f4c$1@news.povray.org>
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"Slime" <fak### [at] emailaddress> wrote...
> > I do like a wee dram but I noticed that when I turned on photons the
> > whisky colour of the shadow went.
>
> This is physically correct. Any light passing through the glass becomes a
> photon. Notice that the photon-covered areas *are* colored, since that
light
> is filtered by the color of the drink. The rest of the shadow is uncolored
> because none of the light hitting that area has passed through the glass.
Correct. It is interesting how our perception of our world often differs
from reality. When I started working on the photon code, I started looking
more closely at real items in the real world, and I noticed that many
shadows of clear objects (such as a glass of water) looked very different
than how I thought they "should" look. The reality is that much of the
shadow area is almost completely black. However, when we casually view
something like a glass of water, if we don't look carefully, our brains have
a tendency to fill in details that really aren't there.
-Nathan
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From: Andrew the Orchid
Subject: Re: Loss of colour in shadow when using photons. - a02a_1xb2.png
Date: 13 Nov 2004 04:15:25
Message: <4195d0ad@news.povray.org>
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> Correct. It is interesting how our perception of our world often differs
> from reality. When I started working on the photon code, I started looking
> more closely at real items in the real world, and I noticed that many
> shadows of clear objects (such as a glass of water) looked very different
> than how I thought they "should" look. The reality is that much of the
> shadow area is almost completely black. However, when we casually view
> something like a glass of water, if we don't look carefully, our brains have
> a tendency to fill in details that really aren't there.
Ah yes - the mind does not always perceive what is before the eye...
(See any optical illusion for a simple proof of this concept.)
Personally, I would suggest that maybe the lightsource is in the wrong
place (and/or should be an area light - do photons respond to those?)
Andrew.
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