I was thinking about this the other night and am not sure how possible or
easy to do it would be.  Would it be possible to make a patched POV that
could use 'ior mapping', i.e., ior values could use something like a density
map for varying ior values within a material.  I was thinking this could
come in handy in some different situations such as mirages or that
appearance you get looking at hot pavement (I can't remember what to call
it) or for modeling of non-homogeneous materials.
I'm not much of a POV programmer myself so I don't think I would be up to
the task, but perhaps someone else is interested in the idea, if it's even
possible.

-tgq

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TinCanMan wrote:
> 
> I was thinking about this the other night and am not sure how possible or
> easy to do it would be.  Would it be possible to make a patched POV that
> could use 'ior mapping', i.e., ior values could use something like a density
> map for varying ior values within a material.  I was thinking this could
> come in handy in some different situations such as mirages or that
> appearance you get looking at hot pavement (I can't remember what to call
> it) or for modeling of non-homogeneous materials.
> I'm not much of a POV programmer myself so I don't think I would be up to
> the task, but perhaps someone else is interested in the idea, if it's even
> possible.

http://www.students.tut.fi/~warp/povQandT/languageQandT.html#variableior

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 02 Jun. 2002 _____./\/^>_*_<^\/\.______

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> http://www.students.tut.fi/~warp/povQandT/languageQandT.html#variableior

Thanks, I think :(
I guess it makes sense that it would be very difficult to solve. Back to the
drawing board (or rendering screen rather)

-tgq

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TinCanMan wrote:
> 
> I was thinking about this the other night and am not sure how possible or
> easy to do it would be.  Would it be possible to make a patched POV that
> could use 'ior mapping', i.e., ior values could use something like a density
> map for varying ior values within a material.  I was thinking this could
> come in handy in some different situations such as mirages or that
> appearance you get looking at hot pavement (I can't remember what to call
> it) or for modeling of non-homogeneous materials.
> I'm not much of a POV programmer myself so I don't think I would be up to
> the task, but perhaps someone else is interested in the idea, if it's even
> possible.
> 
> -tgq

I haven't tried it, but you might be able to get something like it with
a bunch of clear cylinders between you and the mirage, axis of cylinder
perpendicular (or not quite ?) to the camera, different iors in each
cylinder.


-- 
Tom A.
The problem was that Apostles were hard to come by and, worse, they had
a nasty habit of getting crucified or beheaded. -Larry Nolte 
Deja mail is gone.  Look for me at raugost at yahoo . com

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Tom A. <tar### [at] my-dejacom> wrote:
> I haven't tried it, but you might be able to get something like it with
> a bunch of clear cylinders between you and the mirage, axis of cylinder
> perpendicular (or not quite ?) to the camera, different iors in each
> cylinder.

  Remember to raise max_trace_level accordingly and be prepared for a
really long render... ;)

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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> http://www.students.tut.fi/~warp/povQandT/languageQandT.html#variableior


You know, it's not really impossible. It would just require some sort of
approximated integration, Euler's method at the least. I won't argue that it
would be easy to do though; that depends on how POV-Ray works internally.

 - Slime
[ http://www.slimeland.com/ ]

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Slime wrote:
>>
http://www.students.tut.fi/~warp/povQandT/languageQandT.html#variableior
>
> You know, it's not really impossible. It would just
> require some sort of approximated integration,
> Euler's method at the least.

Well, I can't say that I know what I'm talking about, but I think that
even the slightest calculation inaccuracies would lead to big visible
differences from pixel to pixel thus giving a very grainy look. Smooth
variable ior would require render times that would make smooth focal
blur seem like nothing in comparison. ...I think... :)

Rune
--
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Rune's World:  http://rsj.mobilixnet.dk (updated May 20)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Ring:  http://webring.povray.co.uk

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> Well, I can't say that I know what I'm talking about, but I think that
> even the slightest calculation inaccuracies would lead to big visible
> differences from pixel to pixel thus giving a very grainy look. Smooth
> variable ior would require render times that would make smooth focal
> blur seem like nothing in comparison. ...I think... :)


You're probably right, though it would depend on *how* variable the ior was.
f_noise3d scaled very small would be innacurate, but something like a
gradient scaled very large would be much more accurate.

 - Slime
[ http://www.slimeland.com/ ]

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Warp wrote:
> 
> Tom A. <tar### [at] my-dejacom> wrote:
> > I haven't tried it, but you might be able to get something like it with
> > a bunch of clear cylinders between you and the mirage, axis of cylinder
> > perpendicular (or not quite ?) to the camera, different iors in each
> > cylinder.
> 
>   Remember to raise max_trace_level accordingly and be prepared for a
> really long render... ;)
> 
> --//  - Warp -

I just posted an animation on the binaries.animation group that uses an
isofunction to generate heat waves.

Since the question was originally posted here, I thought I'd post a
pointer to it.

And using the single object (admittedly an isosurface) wasn't too bad -
took about 30 seconds per frame, including the 5-10 seconds to parse the
blobman. 

-- 
Tom A.
Avon: I'm going to reprogram this computer.
Jenna: It still won't make you likable. - Blake 7
Deja mail is gone.  Look for me at raugost at yahoo . com

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