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Hola,
I'm working on an idea and I'm not getting the results I expected, so before
I flog this any further, I thought I'd post and see if it's even possible.
For those who don't know what a cross screen filter is ..... check out this
Wikipedia entry:
http://en.wikipedia.org/wiki/Filter_(photography)#Cross_screen
So my question is is this even possible in POV? I've constructed my filter
(I'm using the fine wire grating method) and it dosen't work as expected. I
think I'm missing the "diffraction" element of my filter. Since this is a
pretty sharp group I imagine someone might have a few pointers to get me
going in the right direction .... or tell me that it can't be done.
Cheers Jim
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Jim Holsenback nous apporta ses lumieres en ce 10 / 05 / 2007 19:44:
> Hola,
>
> I'm working on an idea and I'm not getting the results I expected, so before
> I flog this any further, I thought I'd post and see if it's even possible.
> For those who don't know what a cross screen filter is ..... check out this
> Wikipedia entry:
> http://en.wikipedia.org/wiki/Filter_(photography)#Cross_screen
>
> So my question is is this even possible in POV? I've constructed my filter
> (I'm using the fine wire grating method) and it dosen't work as expected. I
> think I'm missing the "diffraction" element of my filter. Since this is a
> pretty sharp group I imagine someone might have a few pointers to get me
> going in the right direction .... or tell me that it can't be done.
>
> Cheers Jim
>
>
Strictly, NO. But, you can have something similar.
POV-Ray don't have diffraction.
You can simulate this effect by using a plane placed between the camera and the
rest of the scene. The filter-box will be totaly transparent (rgbt 1) have some
averaged rotated gradient pattern (to give the rainbow lines) and a flat normal
that is stronger than the rest (heavier ponderation) so that the objects
themself are seen normaly.
You need to give your filter-box an interior with a small ior and a large
dispersion value, maybe larger than that of the ior. You will probably need to
increment the dispersion_samples value over it's default value of 7.
Be ready for long render times. Each averaged normal will generate an additional
ray to be computed, that will bet multiplied by dispersion_samples. So, if you
want a 6 branches effect, you will have at least 49 rays to sample for each pixel.
There is a tool, the lenseflare macro, that does basicaly that.
--
Alain
-------------------------------------------------
An organizer for the "Million Agoraphobics March" expressed disappointment in
the turnout for last weekend's event.
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"Jim Holsenback" <jho### [at] hotmail com> wrote:
> Hola,
>
> I'm working on an idea and I'm not getting the results I expected, so before
> I flog this any further, I thought I'd post and see if it's even possible.
> For those who don't know what a cross screen filter is ..... check out this
> Wikipedia entry:
> http://en.wikipedia.org/wiki/Filter_(photography)#Cross_screen
>
> So my question is is this even possible in POV? I've constructed my filter
> (I'm using the fine wire grating method) and it dosen't work as expected. I
> think I'm missing the "diffraction" element of my filter. Since this is a
> pretty sharp group I imagine someone might have a few pointers to get me
> going in the right direction .... or tell me that it can't be done.
>
> Cheers Jim
The easiest way to do this would be to look at your scene through a thin box
(like a glass lens) with an appropriate ior and a surface normal applied.
You may need to scale the bump size of the grating filter up and the
spacing down to suit your needs. You will also need heavy AA to make it
look good. But it should and does work, I have used similar in the past
for both reflective and refractive surfaces.
-tgq
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> There is a tool, the lenseflare macro, that does basicaly that.
http://www.geocities.com/ccolefax/
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"Tim Attwood" <tim### [at] comcastnet> wrote in message
news:46441bae$1@news.povray.org...
>> There is a tool, the lenseflare macro, that does basicaly that.
> http://www.geocities.com/ccolefax/
Ahhh .... thanks for the link. I'll check it out as I'm not inclined to
reinvent the wheel if I don't have to.
Thanks Jim
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"Tim Attwood" <tim### [at] comcastnet> wrote in message
news:46441bae$1@news.povray.org...
>> There is a tool, the lenseflare macro, that does basicaly that.
> http://www.geocities.com/ccolefax/
that link is dead ..... i found something here:
http://nathan.kopp.com/nkflare.htm
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Jim Holsenback schrieb:
> "Tim Attwood" <tim### [at] comcastnet> wrote in message
> news:46441bae$1@news.povray.org...
>>> There is a tool, the lenseflare macro, that does basicaly that.
>> http://www.geocities.com/ccolefax/
>
> that link is dead ..... i found something here:
> http://nathan.kopp.com/nkflare.htm
>
>
http://www.geocities.com/ccolefax/
is working fine for me. Lots of nice plugins. Thanks
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Tim Attwood nous apporta ses lumieres en ce 11 / 05 / 2007 03:30:
>> There is a tool, the lenseflare macro, that does basicaly that.
> http://www.geocities.com/ccolefax/
>
>
Thanks. I've lost it.
--
Alain
-------------------------------------------------
Methodist: It's not so bad if shit happens, as long as you serve grape juice
with it.
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"Jim Holsenback" <jho### [at] hotmailcom> schreef in bericht
news:46443f8a@news.povray.org...
>
> "Tim Attwood" <tim### [at] comcastnet> wrote in message
> news:46441bae$1@news.povray.org...
>>> There is a tool, the lenseflare macro, that does basicaly that.
>> http://www.geocities.com/ccolefax/
>
> that link is dead ..... i found something here:
> http://nathan.kopp.com/nkflare.htm
>
Nathan's lensflares are better imho.
Thomas
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Jim Holsenback nous apporta ses lumieres en ce 11 / 05 / 2007 06:03:
> "Tim Attwood" <tim### [at] comcastnet> wrote in message
> news:46441bae$1@news.povray.org...
>>> There is a tool, the lenseflare macro, that does basicaly that.
>> http://www.geocities.com/ccolefax/
This works just fine. Maybe you experienced a momentary overload of the server.
>
> that link is dead ..... i found something here:
> http://nathan.kopp.com/nkflare.htm
>
>
The link works, but the internal link for the POV include is broken. That one is
5 years old and made for POV-Ray 3.1 (current is 3.6). Some features of that
version are no longer supported since version 3.5 and have been replaced by
beter solutions.
Note that this used disk, disk have an interior and need to be set to hollow if
you use media or fog. A disk is a chunk of a plane with only a small part
visible. Even then, you can get artefacts.
--
Alain
-------------------------------------------------
A Bill of Rights is what the people are entitled to against every
government, and what no just government should refuse, or rest on inference.
Thomas Jefferson
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