Hi there,

maybe I'm not an advanced user but I need help from one. So I hope this post
isn't OT.
It's about the milky glass problem. It is not an easy task for ANY raytracer
but since I'm working on POV, POV tips are preferred :-)

I need some texture which simulates shining-through-but-not-transparent
objects. The first thing which comes into my mind is a hollow object filled
with scattering media or similar things. Unfortunately I want to apply this
texture onto a mesh which is therefore infinitively thin (at least the
triangles). Does any one know a fancy trick to emulate milky glass by using
a texture?
The object should also be bright in case the light source is BEHIND the
object (like milky glass does). Any way to do this? Please note that it is
about difficult lighting situations with varying arrangement of the objects.
So any hand-trimmed ambient stuff will fail.
It really needs to be a result of a rendering process.

Any hints?
I really got stuck with this.

Thanks in advance,
regards,
SY

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In article <3c72a8b7$1@news.povray.org>,


> I need some texture which simulates shining-through-but-not-transparent
> objects. The first thing which comes into my mind is a hollow object filled
> with scattering media or similar things. Unfortunately I want to apply this
> texture onto a mesh which is therefore infinitively thin (at least the
> triangles). Does any one know a fancy trick to emulate milky glass by using
> a texture?
> The object should also be bright in case the light source is BEHIND the
> object (like milky glass does). Any way to do this? Please note that it is
> about difficult lighting situations with varying arrangement of the objects.
> So any hand-trimmed ambient stuff will fail.

Scattering media is the right thing to use here, it should work fine as 
long as your mesh is "well behaved", meaning it doesn't have any 
internal surfaces or openings.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

Post a reply to this message

> 
> Hi there,
> 
> maybe I'm not an advanced user but I need help from one. So I hope this post
> isn't OT.
> It's about the milky glass problem. It is not an easy task for ANY raytracer
> but since I'm working on POV, POV tips are preferred :-)
> 
> I need some texture which simulates shining-through-but-not-transparent
> objects. The first thing which comes into my mind is a hollow object filled
> with scattering media or similar things. Unfortunately I want to apply this
> texture onto a mesh which is therefore infinitively thin (at least the
> triangles). Does any one know a fancy trick to emulate milky glass by using
> a texture?

Scattering media should be fine for that, no problem with meshes as long
as they are closed of course.  If you need it on a singular mesh surface
you will have to 'double' it to get a closed volume.

See:

http://news.povray.org/3B97ABD4.5E70568D@engineer.com

(no milky glass but a glass of milk, that should not be a problem though)

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 06 Feb. 2002 _____./\/^>_*_<^\/\.______

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> Scattering media should be fine for that, no problem with meshes as long
> as they are closed of course.  If you need it on a singular mesh surface
> you will have to 'double' it to get a closed volume.

That is what I want to avoid. I already have several hunderts of thouthands
triangles. I don't want to double them (or almost triple to close it
properly)

regards
SY

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> Scattering media is the right thing to use here, it should work fine as
> long as your mesh is "well behaved", meaning it doesn't have any
> internal surfaces or openings.

That is the point: it is flat. And since the nr. of triangles is huge I
don't want (can't?) double them to make it closed.
No other way?

regards
SY

Post a reply to this message

In article <3c72cb59$1@news.povray.org>,


> That is the point: it is flat. And since the nr. of triangles is huge I
> don't want (can't?) double them to make it closed.

Well, you are trying to simulate an effect over the interior of the 
object, on an object without an interior...maybe you should explain more 
clearly what you want to do. The double_illuminate flag will let the 
surface be lit from the other side, which might be enough for your 
purposes.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

Post a reply to this message

> 
> > Scattering media should be fine for that, no problem with meshes as long
> > as they are closed of course.  If you need it on a singular mesh surface
> > you will have to 'double' it to get a closed volume.
> 
> That is what I want to avoid. 

That would be difficult.  Or have you ever seen a milky glass of zero
thickness?

> I already have several hunderts of thouthands
> triangles. I don't want to double them (or almost triple to close it
> properly)

It would not be much slower, meshes are very efficient concerning higher
triangle counts.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 06 Feb. 2002 _____./\/^>_*_<^\/\.______

Post a reply to this message

> I need some texture which simulates shining-through-but-not-transparent
> objects. The first thing which comes into my mind is a hollow object filled
> with scattering media or similar things. Unfortunately I want to apply this
> texture onto a mesh which is therefore infinitively thin (at least the
> triangles).

Truth is you CAN apply media to the interior of a triangle. The problem
comes when you try to apply it to an entire mesh object. The remedy,
though not a very attractive one, is to apply the media to each and
every individual triangle in your object. Good luck with the processing
time...

-- 
Ken Tyler

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> Truth is you CAN apply media to the interior of a triangle. The problem

How? I thought a triangle / smooth_triangle doesn't have interiors?

> though not a very attractive one, is to apply the media to each and
> every individual triangle in your object. Good luck with the processing
> time...

Since I already have idividual textures for each triangle, this wouldn't be
a conceptual problem :-)
Processing time.... well..... I don't think it gets larger than the parsing
time right now ;-)

Thanks and regards,
SY

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> It would not be much slower, meshes are very efficient concerning higher
> triangle counts.

Hmmm... But then it would come into millions. I don't think that my PC could
handle that, besinde the huge resulting include file (which is already at 20
to 100 MB depending on LOD)

Thanks and regards
SY

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