I am trying to design a scene wherein a cell (like the ones in our body) 
is filled with granular cytoplasm.  I managed to achieve this effect by 
filling the interior of the cell with hundreds of small spheres. 
However, this is a lot of work, and makes rendering quite slow.  I was 
wondering if there was a way to setup media or interior commands which 
create granular media - i.e. media with large particles, rather then the 
small fog-like particles.

I read through the media tutorial and help files, but couldn't find 
anything close to this.

Thanx in advance

Bryan

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Bryan Heit nous apporta ses lumieres en ce 2005-10-18 16:48:
> I am trying to design a scene wherein a cell (like the ones in our body) 
> is filled with granular cytoplasm.  I managed to achieve this effect by 
> filling the interior of the cell with hundreds of small spheres. 
> However, this is a lot of work, and makes rendering quite slow.  I was 
> wondering if there was a way to setup media or interior commands which 
> create granular media - i.e. media with large particles, rather then the 
> small fog-like particles.
> 
> I read through the media tutorial and help files, but couldn't find 
> anything close to this.
> 
> Thanx in advance
> 
> Bryan
Possibilities:
isosurface using a pattern, like bozo or granite, as a function.
media using a pattern like bozo and a sharp colour_map to modulate density. Use a high
samples count 
rather than many intervals if using the default sampling method, it's faster.
Sample colour_map: color_map{[0.8 rgb 0][0.8 rgb 10]}
 From 0 to 0.8, clear. from 0.8 to 1.0 high density.

The first will give you well deffined edges and allown you to use an interior
statement.
The second will give you somewhat fuzzy shapes.
Both *may* be faster than 100s of small spheres.

-- 
Alain
-------------------------------------------------
Just remember - if the world didn't suck, we would all fall off.

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Bryan Heit <bjh### [at] NOSPAMucalgaryca> wrote:

> I was wondering if there was a way to setup media or interior commands which
> create granular media - i.e. media with large particles, rather then the
> small fog-like particles.
>

> Bryan

I could be wrong, but I think that there is only one "size" of partical in
MEDIA. (And personally, I'd like to know what size that is, for future
reference. I don't see that in the POV docs anywhere. Perhaps it's just a
mathematical "point" with no size at all.)

One way to achieve your results would be to set up an isosurface object,
with suitable values that create lots of tiny broken-up blobby-like pieces.
Alas, long render times would accompany that as well.

Perhaps another method (just a guess) would be to set up a MEDIA / INTERIOR
/ DENSITY block with a density_map or color_map that includes some
transparent "colors", perturb that with a granite
pattern (or turbulence), then apply that 3D result to a sphere. Or "fill"
the sphere
with it.  Or something like that! Can't say that I've tried this, but it
seems like it would work, generally speaking.

Ken

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Kenneth wrote:
> 
> I could be wrong, but I think that there is only one "size" of partical in
> MEDIA. (And personally, I'd like to know what size that is, for future
> reference. I don't see that in the POV docs anywhere. Perhaps it's just a
> mathematical "point" with no size at all.)
> 

As far as I understood the concept and implementation of scattering 
media in POVRay is, that there is no size at all. Instead there are 
empirical scattering function derived for certain aspects and different 
types of scattering media.
I think for scattering to occure the structure (size) which interacts 
with the light have to have about the dimensions of the wavelength of 
the light.

... dave

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Kenneth nous apporta ses lumieres en ce 2005-10-18 17:24:
> Bryan Heit <bjh### [at] NOSPAMucalgaryca> wrote:
> 
> 
>>I was wondering if there was a way to setup media or interior commands which
>>create granular media - i.e. media with large particles, rather then the
>>small fog-like particles.
>>
> 
> 
>>Bryan
> 
> 
> I could be wrong, but I think that there is only one "size" of partical in
> MEDIA. (And personally, I'd like to know what size that is, for future
> reference. I don't see that in the POV docs anywhere. Perhaps it's just a
> mathematical "point" with no size at all.)
> 
> One way to achieve your results would be to set up an isosurface object,
> with suitable values that create lots of tiny broken-up blobby-like pieces.
> Alas, long render times would accompany that as well.
> 
> Perhaps another method (just a guess) would be to set up a MEDIA / INTERIOR
> / DENSITY block with a density_map or color_map that includes some
> transparent "colors", perturb that with a granite
> pattern (or turbulence), then apply that 3D result to a sphere. Or "fill"
> the sphere
> with it.  Or something like that! Can't say that I've tried this, but it
> seems like it would work, generally speaking.
> 
> Ken
> 
> 
> 
> 
> 
There is NO size for the particles in any media. In fact, thare are no particles at
all in any 
media, just sampling points along the line of view.
I made a sample scene using a media with a scaled granite pattern and second media
with a bozo 
pattern. The granite pattern had a color_map like [0.9 rgb 0][1 rgb 10]. It looked
like faling rain, 
just what I was looking for.

-- 
Alain
-------------------------------------------------
AAAAAA: American Association Against Acronym Abuse and Ambiguity.

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