Hey all,

The following 3 pics demonstrate a negative effect that photons are having
on my scene.

(Hopefully, in order) the first one has no glass, the second has glass but
no photons, and the third has both glass and photons.  The pigment for the
glass was rgbf <1,1,1,1> with your basic glass finish.  The brass is a
modified "metals.inc" texture.  The problem is with the brass texture on the
metal pieces inside the glass dome.  Especially the dolphin, which changes
drastically when photons are used.

I've tweaked texture (glass and metal), photon settings, lighting, and
everything I could think of and this is the best that it gets.

Eric
---------------
"A wise and frugal government, which shall restrain men from injuring one
another, which shall leave them otherwise free to regulate their own
pursuits of industry and improvement, and shall not take from the mouth of
labor the bread it has earned.  This is the sum of good government."
     - Thomas Jefferson
     - First inaugural address, 1801
---------------
http://www.ametro.net/~ericfree

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Attachments:
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Preview of image 'trophy4-no_glass.jpg'

Preview of image 'trophy4-no_photons.jpg'

Preview of image 'trophy4-photons.jpg'

Eric Freeman wrote:
> 
> Hey all,
> 
> The following 3 pics demonstrate a negative effect that photons are having
> on my scene.
> 
> (Hopefully, in order) the first one has no glass, the second has glass but
> no photons, and the third has both glass and photons.  The pigment for the
> glass was rgbf <1,1,1,1> with your basic glass finish.  The brass is a
> modified "metals.inc" texture.  The problem is with the brass texture on the
> metal pieces inside the glass dome.  Especially the dolphin, which changes
> drastically when photons are used.

I've heard it said by folks at Pixar that one of the reasons PRMan is
scan-line is that it allows them to ditch physical realism when they
want something that isn't physically realistic.  Is it possible that the
preferred effect isn't physically realistic?

Then again, POV-Ray has a precedent for giving people plenty of room to
be physically unrealistic (media).

-Mark Gordon

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Eric Freeman <eri### [at] ametronet> wrote...
> Hey all,
>
> The following 3 pics demonstrate a negative effect that photons are having
> on my scene.

Try a few experiments and let me know how things turn out:
First, try an IOR of 1.0 for the glass, with no reflection, only refraction.
Second, try a different texture (instead of the brass), such as a
solid-color pigment with only diffuse finish and no 'metallic'.

-Nathan

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Hello Eric,

Actually, the photon patch give excellent results but different from
results obtained without it. I don't speak about caustic but about 
the shape of shadow. If you look your third picture, you see that 
there a dark shadow but not in the second picture. The third picture 
is more realistic. I have made some test with a simple glass of 
wine, the shape of the shadow is really more realistic with photon
because without it, there is almost no dark shadow from the glass. 
But when you look a real glass the shadow is really there and dark! 
Actually in real life all the light goes into the caustic which is 
generally a small bright spot of light with a somewhat complicated
shape. 
And the rest is then dark (and this is not completly black because of 
indirect lightning (which is simulated by ambient or radiosity with 
Povray)).

Now what about your picture? 

If you look your second and third pictures you can see that the 
part below dolphin look almost the same but your dolphin is dark 
in the third picture. Why? because the light doesn't go anymore onto
your dolphin because the light which goes previously on your dolphin
goes now into the caustic! So there is no longer light for your dolphin!

What you can do:

- Change the IOR of the glass
- Change the position of the light
- Try radiosity (This is certainly the physically right way but I am not 
                sure if this will work in your case! And if you do 
                this, put good ambient value (0) to all your objects, 
                etc..)
- Do like professional : add a small spotlight (which doesn't make 
                         shadow) to light your dolphin and play with 
                         the finish of your dolphin.

So this is not the photon method which doesn't work, this is because 
this work in another (good) way. However in the real life you will
certainly see correctly the dolphin but in this case this because 
there are many indirect lightning in real life.

I hope I was clear :)

Fabian.

Eric Freeman wrote:
> 
> Hey all,
> 
> The following 3 pics demonstrate a negative effect that photons are having
> on my scene.
> 
> (Hopefully, in order) the first one has no glass, the second has glass but
> no photons, and the third has both glass and photons.  The pigment for the
> glass was rgbf <1,1,1,1> with your basic glass finish.  The brass is a
> modified "metals.inc" texture.  The problem is with the brass texture on the
> metal pieces inside the glass dome.  Especially the dolphin, which changes
> drastically when photons are used.
> 
> I've tweaked texture (glass and metal), photon settings, lighting, and
> everything I could think of and this is the best that it gets.
> 
> Eric
> ---------------
> "A wise and frugal government, which shall restrain men from injuring one
> another, which shall leave them otherwise free to regulate their own
> pursuits of industry and improvement, and shall not take from the mouth of
> labor the bread it has earned.  This is the sum of good government."
>      - Thomas Jefferson
>      - First inaugural address, 1801
> ---------------
> http://www.ametro.net/~ericfree
> 
>  [Image]
> 
>  [Image]
> 
>  [Image]

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> The pigment for the
>glass was rgbf <1,1,1,1> with your basic glass finish.  The brass is a
>modified "metals.inc" texture.  The problem is with the brass texture on
the
>metal pieces inside the glass dome.  Especially the dolphin, which changes
>drastically when photons are used.
>
>I've tweaked texture (glass and metal), photon settings, lighting, and
>everything I could think of and this is the best that it gets.


I think you need to change the IOR for the glass.  A glass display dome
shouldn't be as distorting as this one is.  Try IOR 1.05 to 1.1 and see.

Good display domes are frequently made of glasses with lower refraction than
'normal' glass for just this reason (although this is probably not the
effect that they are trying to avoid :).

Post a reply to this message

"Brendt Hess" <bhe### [at] rsmedicalcom> wrote in message
news:38838f29@news.povray.org...
>
> I think you need to change the IOR for the glass.  A
> glass display dome shouldn't be as distorting as
> this one is.  Try IOR 1.05 to 1.1 and see.
>
> Good display domes are frequently made of glasses
> with lower refraction than 'normal' glass for just this
> reason (although this is probably not the effect that
> they are trying to avoid :).

Thanks for the tip... I'll give it a try.

Eric
---------------
http://www.ametro.net/~ericfree

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Isn't that dolphin made of triangles?  Maybe it's a problem with the 'mesh'
because the other brass parts don't really change like that does.  Wondering if
'double_illuminate' would make any difference.

Bob

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"omniVERSE" <inv### [at] aolcom> wrote in message
news:38840b14@news.povray.org...
>
> Isn't that dolphin made of triangles?

Yep.

> Maybe it's a problem with the 'mesh' because the
> other brass parts don't really change like that does.
> Wondering if 'double_illuminate' would make any
> difference.

double_illuminate?  double_illuminate???  Hmmm... time to RTFM.

Eric
---------------
"A wise and frugal government, which shall restrain men from injuring one
another, which shall leave them otherwise free to regulate their own
pursuits of industry and improvement, and shall not take from the mouth of
labor the bread it has earned.  This is the sum of good government."
     - Thomas Jefferson
     - First inaugural address, 1801
---------------
http://www.ametro.net/~ericfree

Post a reply to this message