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David Anderson wrote:
>
> Hi all!
>
> I am new to the raytracing world, and I would like to redo the halo effect
> from povray 3.0 in 3.1 . How do I do so???? The help vaguely speaks of the
> media object, but that's about all I know...
>
> Thanks In Advance
> Me!!!
The parameters have not changed all that much though they do not
necessarily work exactly the same. I personally believe it is easier
to just forget what you know about the halo feature and learn the
media feature from the start. That way you won't have any preconceived
notions about how it should work and become disappointed when it doesn't
do what you think it should.
Here are a couple of links to mini tutorials on the new media feature:
http://members.xoom.com/POVRAY3/media1.html
http://members.xoom.com/POVRAY3/media2.html
--
Ken Tyler
See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html
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I think the basic thing to do is use 'density' and 'density_map' like
you would with 'color_map' in 'halo', putting the type (spherical for
example) into the density statement. And use emission or absorption
in place of the rgbt -1 and dust type. It's no direct exchange but
once you learn the workings a halo can be faked fairly okay. Like Ken
said though probably better to move into media entirely and just skip
halo "conversion". Don't forget about 'scattering' if you need to
interact with light.
Bob
Ken <tyl### [at] pacbell net> wrote in message
news:37D### [at] pacbellnet...
>
>
> David Anderson wrote:
> >
> > Hi all!
> >
> > I am new to the raytracing world, and I would like to redo the
halo effect
> > from povray 3.0 in 3.1 . How do I do so???? The help vaguely
speaks of the
> > media object, but that's about all I know...
> >
> > Thanks In Advance
> > Me!!!
>
> The parameters have not changed all that much though they do not
> necessarily work exactly the same. I personally believe it is easier
> to just forget what you know about the halo feature and learn the
> media feature from the start. That way you won't have any
preconceived
> notions about how it should work and become disappointed when it
doesn't
> do what you think it should.
>
> Here are a couple of links to mini tutorials on the new media
feature:
>
> http://members.xoom.com/POVRAY3/media1.html
> http://members.xoom.com/POVRAY3/media2.html
>
> --
> Ken Tyler
>
> See my 850+ Povray and 3D Rendering and Raytracing Links at:
> http://home.pacbell.net/tylereng/index.html
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Bob Hughes <inv### [at] aolcom> wrote in message
news:37dcfecc@news.povray.org...
> I think the basic thing to do is use 'density' and 'density_map' like
> you would with 'color_map' in 'halo', putting the type (spherical for
> example) into the density statement. And use emission or absorption
> in place of the rgbt -1 and dust type. It's no direct exchange but
> once you learn the workings a halo can be faked fairly okay. Like Ken
> said though probably better to move into media entirely and just skip
> halo "conversion". Don't forget about 'scattering' if you need to
> interact with light.
Halo had the "glowing" keyword ( = emitting and absorbing) , which
probably ought to be done as a macro in 3.1, becuae it is very often the
Right Thing. Specifically, thermodynamics tells us that glowing media
(flames, red hot glass, neon, etc.) absorb and emit the same spectrum. This
means that in most places where one might naively expect to use "emission 1"
one should in fact use "emission 1 absorption 1". Emitting media on their
own almost always look wrong. (Perhaps Fluorescent media might be an
exception? I'm not sure here.) Pure absorbing media, on the other hand, do
have their place, as do scattering media...
But when in doubt, use equal parts of emission and absorbtion rather
than pure emission.
-Robert Dawson
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