Hi,
	I've not played with the media since the halo statement doesn't exist
anymore...
I'll make it simple, how can I make a halo sphere...  on a black background a
white spherish cloud should apear as the light flows through (ie: constant
density, reflect color of light as rgb 1)

Thanks,
	Simon

Post a reply to this message

Simon Lemieux <lem### [at] yahoocom> wrote:
> I've not played with the media since the halo statement doesn't exist
> anymore...
> I'll make it simple, how can I make a halo sphere...  on a black
background a
> white spherish cloud should apear as the light flows through (ie: constant
> density, reflect color of light as rgb 1)

Simple answer:

   sphere {0, 1 hollow
      pigment {rgbf 1}
      interior {media {emission rgb 1}}
      }

You can vary the colour and density by adjusting the emission.  If you want
to do more with the ball of media (such as apply turbulence), use a density
map:

   sphere {0, 2 hollow
      pigment {rgbf 1}
      interior {media {emission rgb 1
         density {spherical
            color_map {[0 rgb 0] [1 rgb 1]}
            turbulence 0.5 lambda 3
            }}}}

The values in the color map(s) of your density map(s) are multiplied by the
emission, absorption and scattering values of your media, so using rgb 0
gives a transparent media (and rgb 1 gives media having the values you
originally specified).  As soon as you use a density map, however, you will
notice the poor results of the default sampling methods.  This is where
MegaPOV's extra sampling methods make a huge difference (and just wait till
you start using scattering media...!).

Post a reply to this message

In article <3994C91B.83A136DB@yahoo.com>, lem### [at] yahoocom wrote:

> Hi,
> 	I've not played with the media since the halo statement doesn't exist
> anymore... I'll make it simple, how can I make a halo sphere...  on a 
> black background a white spherish cloud should apear as the light 
> flows through (ie: constant density, reflect color of light as rgb 1)

I assume you want the halo effect seen around light sources in fog...
You need to use one of the scattering functions other than isotropic. 
Mie hazy and Mie murky(types 2 and 3) should work well. Rayleigh(4) 
might work under some circumstances, Heyney-Greenstein(5) could give you 
more control over the size of the "halo".

You could also "cheat" by using emitting media with a spherical density 
function...but you said you wanted constant density, so I guess this 
isn't what you want.

If you want good results with a reasonable render time, use MegaPOV, 
which has additional sampling methods which can give smoother results 
with less rendering time.

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

Post a reply to this message

> > Hi,
> >       I've not played with the media since the halo statement doesn't exist
> > anymore... I'll make it simple, how can I make a halo sphere...  on a
> > black background a white spherish cloud should apear as the light
> > flows through (ie: constant density, reflect color of light as rgb 1)
> 
> I assume you want the halo effect seen around light sources in fog...
> You need to use one of the scattering functions other than isotropic.
> Mie hazy and Mie murky(types 2 and 3) should work well. Rayleigh(4)
> might work under some circumstances, Heyney-Greenstein(5) could give you
> more control over the size of the "halo".
> 
> You could also "cheat" by using emitting media with a spherical density
> function...but you said you wanted constant density, so I guess this
> isn't what you want.
> 
> If you want good results with a reasonable render time, use MegaPOV,
> which has additional sampling methods which can give smoother results
> with less rendering time.

Actually I was hopping to get a real cloud effect in wich the particles reflect
the light that comes on it and also stop the light from passing through it...
The scattering doesn't give me any of these, but I might not understand how to
use it...

Thanks,
	Simon

Post a reply to this message

> I assume you want the halo effect seen around light sources in fog...
> You need to use one of the scattering functions other than isotropic.
> Mie hazy and Mie murky(types 2 and 3) should work well. Rayleigh(4)
> might work under some circumstances, Heyney-Greenstein(5) could give you
> more control over the size of the "halo".

Here, I've tried the code below, but it doesn't give me anything, my object is
plain transparent and we can see some darkened outline, but that looks more like
a bug since the object is pigment {rgbf 1}...

texture {
  pigment { color rgbf 1 }
}
interior {
  media {
    absorption 1
    emission 1
    scattering { 2, rgb 1 extinction 1 }
  }
}


Is there any global_settings I need to turn on to see a cloud? Is there
something I'm missing?

Thanks,
	Simon

Post a reply to this message

In article <39956DCF.7778D152@yahoo.com>, lem### [at] yahoocom wrote:

> Actually I was hopping to get a real cloud effect in wich the 
> particles reflect the light that comes on it and also stop the light 
> from passing through it...
> The scattering doesn't give me any of these, but I might not 
> understand how to use it...

Actually, scattering media does simulate the dimming of light passing 
through media...make a sphere with a white pigment with a filter of 
1(not transmit, filter), fill it with scattering media, and it will 
leave a shadow which is darker in the denser/thicker areas. The same 
goes for absorption media, though absorption doesn't calculate light 
reflecting from the media, so you won't see light rays through it like 
you can with scattering.

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

Post a reply to this message

Simon Lemieux wrote:

>  Is there something I'm missing?

Light ?

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

Post a reply to this message

> Light ?

Nope, there are two...

Here is my scene:
camera { 
	ultra_wide_angle
	angle 45
	location <0, 6,0>
	look_at <0,0,0>
}

light_source { <100,100,100> color rgb 1  media_interaction on media_attenuation
on}
light_source { <-100,-100,-100> color rgb 1 media_interaction on
media_attenuation on }

are the media_ stuff in the light_source def very necessary?

Thanks,
	Simon

Post a reply to this message

> Actually, scattering media does simulate the dimming of light passing
> through media...make a sphere with a white pigment with a filter of
> 1(not transmit, filter), fill it with scattering media, and it will
> leave a shadow which is darker in the denser/thicker areas. The same
> goes for absorption media, though absorption doesn't calculate light
> reflecting from the media, so you won't see light rays through it like
> you can with scattering.

Yes I know, I have understood that (I think) if the filter is replaced by a
transmit you get no shadow... etc...

but it just doesn't work out for my object...
Can I set a media to a blob object?

Thanks,
	Simon

Post a reply to this message

In article <39957086.94D58FFE@yahoo.com>, lem### [at] yahoocom wrote:

> Here, I've tried the code below, but it doesn't give me anything, my 
> object is plain transparent and we can see some darkened outline, but 
> that looks more like a bug since the object is pigment {rgbf 1}...
> 
> Is there any global_settings I need to turn on to see a cloud? Is there
> something I'm missing?

What is the object containing the media? Media is dependant on scale, 
larger objects need a less dense media to get the same effect.
Also, for this effect, you don't need emission or absorption media. And 
you should specify samples and intervals, the defaults don't work well, 
especially for scattering media. Oh, and make sure the container object 
has "hollow" specified.

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

Post a reply to this message