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From: Dave Dunn
Subject: Traunslucency Without Media MIP
Date: 9 Jul 2002 21:35:45
Message: <3D2B8F65.AD2E3E12@aol.com>
Here is an image that came out of a discussion in our Thrursday night
POV-Ray chat on AOL. The idea was to obtain a subsurface scattering
effect without using media, just to see if it could be done. While far
from perfect, this method shows promise, but is very slow.


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From: Marc Jacquier
Subject: Re: Traunslucency Without Media MIP
Date: 10 Jul 2002 01:53:42
Message: <3d2bcbe6$1@news.povray.org>

3D2B8F65.AD2E3E12@aol.com...
> Here is an image that came out of a discussion in our Thrursday night
> POV-Ray chat on AOL. The idea was to obtain a subsurface scattering
> effect without using media, just to see if it could be done. While far
> from perfect, this method shows promise, but is very slow.
May we know? :)
concentrical semi-transparent spheres?
And is it faster than a scattering media?
C U
Marc


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From: Steve
Subject: Re: Traunslucency Without Media MIP
Date: 10 Jul 2002 05:31:40
Message: <slrnainusr.aol.steve@zeropps.org.uk>
On Tue, 09 Jul 2002 21:35:33 -0400, Dave Dunn wrote:
> 
> Here is an image that came out of a discussion in our Thrursday night
> POV-Ray chat on AOL. The idea was to obtain a subsurface scattering
> effect without using media, just to see if it could be done. While far
> from perfect, this method shows promise, but is very slow.

It'd be interesting to know what method you used. 

-- 
%HAV-A-NICEDAY                    email mailto:ste### [at] zeroppsuklinuxnet
Steve                                web http://www.zeropps.uklinux.net/
                                             or http://start.at/zero-pps
 10:16am  up 12 days, 20:35,  1 user,  load average: 1.09, 1.09, 1.02


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From: Dave Dunn
Subject: Re: Traunslucency Without Media MIP
Date: 10 Jul 2002 10:54:34
Message: <3D2C4A9D.E20B02E0@aol.com>
Marc Jacquier wrote:

> concentrical semi-transparent spheres?
> And is it faster than a scattering media?
> C U
> Marc

I'm impressed. Progressively transparent is more like it, as the loop
increses the filter value and the rgb value, and decreases the roughness and
diffuse value as the spheres get bigger. Not really faster, or better than
media yet, just different.


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From: Samuel Benge
Subject: Re: Traunslucency Without Media MIP
Date: 10 Jul 2002 14:04:55
Message: <3D2C773D.1010907@caltel.com>
Glad to see you're still posting here, Dave :) Have you tried this trick 
using cylinders, cones and torii in csg operations yet? Those objects 
should take well to linear transformations, as opposed to blobs and 
isosurfaces which may give strange results using this technique.

Dave Dunn wrote:

> Here is an image that came out of a discussion in our Thrursday night
> POV-Ray chat on AOL. The idea was to obtain a subsurface scattering
> effect without using media, just to see if it could be done. While far
> from perfect, this method shows promise, but is very slow.
> 
> 
> 
> 
> 
> 
> ------------------------------------------------------------------------
> 


-- 
Samuel Benge

sbe### [at] caltelcom


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From: Dave Dunn
Subject: Re: Traunslucency Without Media MIP
Date: 10 Jul 2002 15:43:36
Message: <3D2C8E59.18EFAF5A@aol.com>
Samuel Benge wrote:

> Glad to see you're still posting here, Dave :) Have you tried this trick
> using cylinders, cones and torii in csg operations yet? Those objects
> should take well to linear transformations, as opposed to blobs and
> isosurfaces which may give strange results using this technique.

As a matter of fact, I am currently working on a couple of crayons using this
technique, involving CSG of a cylinder and a cone, scaled in two directions.
If it works out, I will post.


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From: Skip Talbot
Subject: Re: Traunslucency Without Media MIP
Date: 10 Jul 2002 16:33:37
Message: <3d2c9a21$1@news.povray.org>
I tried doing this myself a few weeks ago and the results using concentric
spheres were significantly slower then media.  I thought this was a similar
technique to the stacked-planes-clouds which are remarkably faster then
scattering media clouds.  I must be mistaken somewhere.

Skip


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From: Marc Jacquier
Subject: Re: Traunslucency Without Media MIP
Date: 10 Jul 2002 16:51:28
Message: <3d2c9e50$1@news.povray.org>
BTW if you want hi Q stacked clouds , you need a lot of planes and it
becomes slower and slower
Marc

3d2c9a21$1@news.povray.org...
> I tried doing this myself a few weeks ago and the results using concentric
> spheres were significantly slower then media.  I thought this was a
similar
> technique to the stacked-planes-clouds which are remarkably faster then
> scattering media clouds.  I must be mistaken somewhere.
>
> Skip
>
>


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From: Dave Dunn
Subject: Re: Traunslucency Without Media MIP
Date: 10 Jul 2002 22:03:04
Message: <3D2CE74B.2916C3F8@aol.com>
Skip Talbot wrote:

> I tried doing this myself a few weeks ago and the results using concentric
> spheres were significantly slower then media.  I thought this was a similar
> technique to the stacked-planes-clouds which are remarkably faster then
> scattering media clouds.  I must be mistaken somewhere.

Well, as I said, I just started playing with this method. The thing I like
about it is that it gives you a lot of control over things that happen
incrementally "inside" your composite object. By incrementing and decrementing
features (such as roughness), you can get some interesting effects. I don't
think it's any better than media, overall, just an interesting thought
exercise. The slowness factor, in my case, was a max_trace_level of 100, for
100 nested spheres. I believe the falloff is much sooner than that, and I
probably could have gotten by with a lower trace level. More on this method
when the crayons are finished.

Dave


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From: Jamie Davison
Subject: Re: Traunslucency Without Media MIP
Date: 11 Jul 2002 15:54:06
Message: <MPG.1797f33af91f8e37989b84@news.povray.org>
> > I tried doing this myself a few weeks ago and the results using concentric
> > spheres were significantly slower then media.  I thought this was a similar
> > technique to the stacked-planes-clouds which are remarkably faster then
> > scattering media clouds.  I must be mistaken somewhere.
> 
> Well, as I said, I just started playing with this method. The thing I like
> about it is that it gives you a lot of control over things that happen
> incrementally "inside" your composite object. By incrementing and decrementing
> features (such as roughness), you can get some interesting effects. I don't
> think it's any better than media, overall, just an interesting thought
> exercise. The slowness factor, in my case, was a max_trace_level of 100, for
> 100 nested spheres. I believe the falloff is much sooner than that, and I
> probably could have gotten by with a lower trace level. More on this method
> when the crayons are finished.

Hmm...  To really slow things down, would there be any way to use the 
trick to simulate variable internal IOR, however crudely?

It would probably require an obscenely high max_trace_level though.

And i can't remember if you can apply a pattern to the surface iro or 
not, as I't sbeen a while since I played with POV.

Jamie.


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