Hi All,
I have been using POVRAY to generate explosion movies. My first question is
that how is it that density has been linked to the color of the media and
there is no facility to specify the transparency of the media in POVRAY? If
we look in particular at explosion then color is a function of temperature
and transparency is a function of density.

Can anyone please suggest how the transparency of the media can be
specified?

Thanks a lot
Maurya
http://www-scf.usc.edu/~mauryash

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Maurya Shah <mau### [at] hotmailcom> wrote:
> Can anyone please suggest how the transparency of the media can be
> specified?

  The color specifies both the color and the transparency of the media.

  In chromatic terms, the hue/saturation of the color specify its color,
and the brightness specifies its transparency.

  That is, for example if you want an orange media you would use
rgb <1, .5, 0>. If you want to make it more transparent, diminish its
brightness. For example if you want to increase its transparency
by half, use rgb <.5, .25, 0>.

  The color of the density specifies how the light passing through it
is filtered.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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news:40288afc$1@news.povray.org...

> Can anyone please suggest how the transparency of the media can be
> specified?

In media scattering, the extinction keyword gives more control on
"transparency" (actually absorption) for artistic purposes.

Btw, the explosion pics on your site are very nice. Is a full animation
available ? And would the code be available for a patched version of
POV-Ray?

G.
-- 

**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters

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Hi Gilles,
Thanks for your comments.
Unfortunately I cannot give a full movie right now, I have to take certain
permissions.
However, I would certainly love to contribute back to POVRAY.
The features I have added so far are -

1) Hermite interpolation - its better because it gives smoother
interpolation and uses more information
2) Given a density mass, the user can specify a threshold and an epsilon, so
that all the values below
     threshold-epsilon are clamped to zero and and those between threshold
to threshold-epsilon are
     smoothly interpolated towards zero. This is basically to get different
shapes with the same density
     volume without getting any artifiacts due to truncation by a threshold.
3)  Use of temperature instead of density to specify the color of the media.
Adding perlin noise to the
     color values to simulate the details.

I am new to the open source community and not quite sure of the procudures
involved in here. But
surely if these features are useful to others I will be glad to clean them
up first and share it with others.

Regards,
Maurya
http://www-scf.usc.edu/~mauryash




"Gilles Tran" <tra### [at] inapginrafr> wrote in message
news:4028cca7@news.povray.org...

> news:40288afc$1@news.povray.org...
>
> > Can anyone please suggest how the transparency of the media can be
> > specified?
>
> In media scattering, the extinction keyword gives more control on
> "transparency" (actually absorption) for artistic purposes.
>
> Btw, the explosion pics on your site are very nice. Is a full animation
> available ? And would the code be available for a patched version of
> POV-Ray?
>
> G.
> --
>
> **********************
> http://www.oyonale.com
> **********************
> - Graphic experiments
> - POV-Ray and Poser computer images
> - Posters
>
>

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In article <402b0c90@news.povray.org>,
 "Maurya Shah" <mau### [at] hotmailcom> wrote:

> 1) Hermite interpolation - its better because it gives smoother
> interpolation and uses more information

Interpolation of what? Is this some kind of spline-based integration for 
media, like Simpson's rule, or is it a new spline type? Or something 
else?


> 2) Given a density mass, the user can specify a threshold and an 
> epsilon, so that all the values below threshold-epsilon are clamped 
> to zero and and those between threshold to threshold-epsilon are 
> smoothly interpolated towards zero. This is basically to get  
> different shapes with the same density volume without getting any 
> artifiacts due to truncation by a threshold.

I'm not sure of what use this is. It sounds fairly trivial to do with a 
function pattern.


> 3)  Use of temperature instead of density to specify the color of the media.

How is this different from just using a density pattern and density map? 
Sounds like just a multiplier for the density color...


> Adding perlin noise to the color values to simulate the details.

Could you explain further? Are you adjusting the final computed values, 
some kind of 2D modulation of the media?


> I am new to the open source community and not quite sure of the 
> procudures involved in here. But surely if these features are useful 
> to others I will be glad to clean them up first and share it with 
> others.

Well, first, POV isn't open source. ;-)
The source code is available, and it is allowed for you to distribute 
modified versions, but there are more restrictions than what you get in 
a "true Open Source" license.
Just clearly mark the locations of your changes/additions, and 
distribute the modified files, or if the patch is simple enough, the 
modified portions and instructions on where to put them. It'd be a good 
idea to follow the MegaPOV conventions...that's about as standard as it 
gets. More info here:
http://megapov.inetart.net/manual/internals.html

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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On Tue, 10 Feb 2004 13:24:35 +0100, "Gilles Tran" <tra### [at] inapginrafr>
wrote:

>Btw, the explosion pics on your site are very nice. Is a full animation
>available ? And would the code be available for a patched version of
>POV-Ray?

I must assure you the animations are incredible (Maurya contacted me
some time ago about this project).


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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