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> 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
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In article <39957086.94D58FFE@yahoo.com>, lem### [at] yahoo com 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/
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In article <39957651.C3CABCC2@yahoo.com>, lem### [at] yahoocom wrote:
> 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?
Media will work with any object that has an inside and outside,
including blobs.
--
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/
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"Simon Lemieux" <lem### [at] yahoocom> wrote in message
news:399575D2.7DCAB36E@yahoo.com...
|
| are the media_ stuff in the light_source def very necessary?
Not if you want the default which is media interaction on and media
attenuation is off by default and is for fading with distance. So you don't
really have to put anything into the light source to see media.
You don't need anything in global settings either, not for the usual uses in
official POV-Ray anyhow.
You might want to try putting a density into your media though. Although it
should be showing that something is there without it too. But a density
{rgb 1} might be worth a try anyhow.
The scattering amount you have is fairly high I believe so you might also
try 0.1 for that and see what shows up.
Bob
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don't folks have problems when samples isn't high enough or am i
thinking of something else?
Simon Lemieux wrote:
>
> > 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
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Hi Simon,
Do you have the 'hollow' keyword in your object? You don't mention it in
your posts, so it may have slipped your mind.
Use as
object {
My_Object
texture { ... }
interior { ... }
hollow
}
Also, to speed up tests I usually have a fast approximation set up, such
as
media {
#if (Test)
intervals 1
samples 3,3
absorption 1
emission 1
#else
intervals 3
samples 5,5
scattering { 2, rgb 1 extinction 1 }
#end
density { ... }
}
then set Test to true for a fast test or false for a propper render.
I don't usually use scattering as well as absorption/emission in one
media, though you can for certain effects.
Bye for now,
Mike Andrews.
Simon Lemieux wrote:
>
> > 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
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> Not if you want the default which is media interaction on and media
> attenuation is off by default and is for fading with distance.
I was thinking about a cloud... so the media attenuation should be set to on...
no? so there is a shadow?
Thanks,
Simon
--
+-------------------------+----------------------------------+
| Simon Lemieux | http://connect.to/666Mhz |
| lem### [at] yahoocom | POV-Ray, OpenGL, C++ and more... |
+-------------------------+----------------------------------+
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> Do you have the 'hollow' keyword in your object? You don't mention it in
> your posts, so it may have slipped your mind.
Yes I had forgotten it, I added the keyword and got a slight success with the
cloud... but was it really a cloud??? Time to tweak the values I entered!... ;)
> Also, to speed up tests I usually have a fast approximation set up, such
> as
>
> media {
> #if (Test)
> intervals 1
> samples 3,3
> absorption 1
> emission 1
> #else
> intervals 3
> samples 5,5
> scattering { 2, rgb 1 extinction 1 }
> #end
> density { ... }
> }
>
> then set Test to true for a fast test or false for a propper render.
Thanks for the advice I like to get a fast preview of things when I render, but
since it's a cloud and it's not very important I was thinking of not giving it
an interior and setting its color to rgb 1 so i can see a shadow but it not very
perfect but still very fast!...
Thanks a lot,
Simon
--
+-------------------------+----------------------------------+
| Simon Lemieux | http://connect.to/666Mhz |
| lem### [at] yahoocom | POV-Ray, OpenGL, C++ and more... |
+-------------------------+----------------------------------+
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"Simon Lemieux" <lem### [at] yahoocom> wrote in message
news:39989DCF.CCBA8544@yahoo.com...
| > Not if you want the default which is media interaction on and media
| > attenuation is off by default and is for fading with distance.
|
| I was thinking about a cloud... so the media attenuation should be set to
on...
| no? so there is a shadow?
Not shadow exactly, it's a 'fade_distance' relationship. You would need to
use that keyword in the light source(s) in order to "attenuate" first then
with it set to on to diminish the light according to that distance and also
'fade_power'.
At least that's how I'm thinking it goes. Just looked it up in the scene
help and it's not said to be based solely on fading. Anyone else know for
sure?
If media/fog attenuates lights without a specified fade then it must be a
fixed default.
Bob
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"Bob Hughes" <per### [at] aolcom?subject=PoV-News:> wrote in message
news:3998d8c1$1@news.povray.org...
| "Simon Lemieux" <lem### [at] yahoocom> wrote in message
| news:39989DCF.CCBA8544@yahoo.com...
| | > Not if you want the default which is media interaction on and media
| | > attenuation is off by default and is for fading with distance.
| |
| | I was thinking about a cloud... so the media attenuation should be set
to
| on...
| | no? so there is a shadow?
What I said below is wrong. Sorry for the mistake.
| Not shadow exactly, it's a 'fade_distance' relationship. You would need
to
| use that keyword in the light source(s) in order to "attenuate" first then
| with it set to on to diminish the light according to that distance and
also
| 'fade_power'.
| At least that's how I'm thinking it goes. Just looked it up in the scene
| help and it's not said to be based solely on fading. Anyone else know for
| sure?
I'll answer my own question. There is apparently attenuation of a fog or
media based on those themselves and not on fade distance or power.
| If media/fog attenuates lights without a specified fade then it must be a
| fixed default.
I'm guessing it's simply by amount of fog or media alone. So, for example,
when fog thickens with distance so to does the light when 'media_attenuation
on' is used in the light source. Same goes for media.
It would seem that fade_distance fade_power is a separate entity unto
itself, only for doing the light source and not associated in any way with
media_interaction and media_attenuation (not directly anyhow). Still, I'm
not %100 sure of this but that would be how it seems described in the
documentation.
Bob
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