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Test animation of a sunrise using media and radiosity. The atmosphere is created
using Rayleigh scattering media which has a density that falls off exponentially
with height. The test is only partially successful: it seems that the media
atmosphere is not giving any contribution to the radiosity lighting. Still have
to figure out if there's any way to increase the contribution of the scattering
media to the radiosity while still allowing the colour of the sky to remain
visible.
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Attachments:
Download 'mediaatmosphere.mpg' (252 KB)
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"ajtribick" <nomail@nomail> wrote:
> Test animation of a sunrise using media and radiosity. The atmosphere is created
> using Rayleigh scattering media which has a density that falls off exponentially
> with height. The test is only partially successful: it seems that the media
> atmosphere is not giving any contribution to the radiosity lighting. Still have
> to figure out if there's any way to increase the contribution of the scattering
> media to the radiosity while still allowing the colour of the sky to remain
> visible.
Did you forget hollow?
Take a look at the (short) source code for "Dawn over the mountains":
http://ozviz.wasp.uwa.edu.au/~pbourke/exhibition/scc4/final/
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"nemesis" <nam### [at] gmail com> wrote:
> "ajtribick" <nomail@nomail> wrote:
> > Test animation of a sunrise using media and radiosity. The atmosphere is created
> > using Rayleigh scattering media which has a density that falls off exponentially
> > with height. The test is only partially successful: it seems that the media
> > atmosphere is not giving any contribution to the radiosity lighting. Still have
> > to figure out if there's any way to increase the contribution of the scattering
> > media to the radiosity while still allowing the colour of the sky to remain
> > visible.
>
> Did you forget hollow?
>
> Take a look at the (short) source code for "Dawn over the mountains":
> http://ozviz.wasp.uwa.edu.au/~pbourke/exhibition/scc4/final/
If I'd forgotten hollow, I wouldn't have got any sky effects at all - the sky
color is media. The issue is the radiosity, which isn't used in that "Dawn over
the mountains" image.
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"ajtribick" <nomail@nomail> wrote:
> The test is only partially successful: it seems that the media
> atmosphere is not giving any contribution to the radiosity lighting.
There does indeed seem to be a current problem with media in objects not
contributing radiosity lighting to other objects *within* the media. Objects
*outside* do receive rad from it, objects within don't. I've spent considerable
time trying to find workarounds, but no luck. Hopefully v 3.7 will solve this
thorny problem.
Ken W.
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"Kenneth" <kdw### [at] earthlinknet> wrote:
> "ajtribick" <nomail@nomail> wrote:
>
> > The test is only partially successful: it seems that the media
> > atmosphere is not giving any contribution to the radiosity lighting.
>
> There does indeed seem to be a current problem with media in objects not
> contributing radiosity lighting to other objects *within* the media. Objects
> *outside* do receive rad from it, objects within don't. I've spent considerable
> time trying to find workarounds, but no luck. Hopefully v 3.7 will solve this
> thorny problem.
>
> Ken W.
Yes the testing I have been doing since I made this animation led me to the same
conclusion. Has this been reported in an official bug reports forum?
Post a reply to this message
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"ajtribick" <nomail@nomail> wrote:
> Yes the testing I have been doing since I made this animation led me to the same
> conclusion. Has this been reported in an official bug reports forum?
Don't know. While experimenting with this last year, I Google'ed the subject
and came across an *old* bug report (or message thread) that mentioned the same
thing. I assumed that the POV team was aware of it. They probably are; it must
be a difficult problem to solve (perhaps tied in with transparency issues.)
In looking back over my own POV test scene (and its MANY notes), I see that I
*did* come up with a workaround. An odd one, to be sure. Try this: Make a
small sphere, out of camera view, fill it with media, then INVERSE the sphere.
According to my notes, that 'fills the universe' with media, and the scene no
longer shows those radiosity problems! (But to see the media, there needs to be
a 'background object' in this case, like a large flat box way off in the
distance, filling the frame, for the media to appear against. The box could be
textured with some kind of sky pigment or pattern, in your case.)
I'll do some tests again, to see if this is an 'always-true' workaround.
My notes also tell me that plain 'atmospheric' media--that is, not enclosed in
an object--works well too; no rad problems. I'll try that again as well.
KW
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"Kenneth" <kdw### [at] earthlinknet> wrote:
> Try this: Make a
> small sphere, out of camera view, fill it with media, then INVERSE the sphere.
> According to my notes, that 'fills the universe' with media, and the scene no
> longer shows those radiosity problems!
Well...I can't seem to reproduce that result now. I don't remember how I came up
with that idea, but it doesn't work (although my old notes say it does.) Can't
trust those old notes. :-$
Sorry for sending you on a wild goose chase! I'll continue to try and figure out
my error...
Ken W.
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"ajtribick" <nomail@nomail> wrote in message
news:web.48fb31f9ed540e8abc82ce420@news.povray.org...
> Test animation of a sunrise using media and radiosity. The atmosphere is
> created
> using Rayleigh scattering media which has a density that falls off
> exponentially
> with height. The test is only partially successful: it seems that the
> media
> atmosphere is not giving any contribution to the radiosity lighting. Still
> have
> to figure out if there's any way to increase the contribution of the
> scattering
> media to the radiosity while still allowing the colour of the sky to
> remain
> visible.
Just a thought... As you are having a problem getting the media to
contribute to the radiosity of objects within the object containing the
media, why not excavate a volume for the objects from that object as
follows:
union
{
difference
{
sphere{0, 100000}
sphere{0, 1000}
interior{media{...}}
}
union
{
//Other objects all within the inner sphere above
}
}
Rarius
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Kenneth nous illumina en ce 2008-10-21 19:48 -->
> "Kenneth" <kdw### [at] earthlinknet> wrote:
>> Try this: Make a
>> small sphere, out of camera view, fill it with media, then INVERSE the sphere.
>> According to my notes, that 'fills the universe' with media, and the scene no
>> longer shows those radiosity problems!
>
> Well...I can't seem to reproduce that result now. I don't remember how I came up
> with that idea, but it doesn't work (although my old notes say it does.) Can't
> trust those old notes. :-$
>
> Sorry for sending you on a wild goose chase! I'll continue to try and figure out
> my error...
>
> Ken W.
>
Filling an inverted sphere out of view is akind of filling the whole scene with
uncontained media. You don't need the sphere, just the media definition.
--
Alain
-------------------------------------------------
When you can't tell the difference between satire and what your opposition
actually believes, its about time to have a good laugh at it all
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Rarius nous illumina en ce 2008-10-23 04:45 -->
> "ajtribick" <nomail@nomail> wrote in message
> news:web.48fb31f9ed540e8abc82ce420@news.povray.org...
>> Test animation of a sunrise using media and radiosity. The atmosphere is
>> created
>> using Rayleigh scattering media which has a density that falls off
>> exponentially
>> with height. The test is only partially successful: it seems that the
>> media
>> atmosphere is not giving any contribution to the radiosity lighting. Still
>> have
>> to figure out if there's any way to increase the contribution of the
>> scattering
>> media to the radiosity while still allowing the colour of the sky to
>> remain
>> visible.
>
> Just a thought... As you are having a problem getting the media to
> contribute to the radiosity of objects within the object containing the
> media, why not excavate a volume for the objects from that object as
> follows:
>
> union
> {
> difference
> {
> sphere{0, 100000}
> sphere{0, 1000}
> interior{media{...}}
> }
> union
> {
> //Other objects all within the inner sphere above
> }
> }
>
> Rarius
>
>
Similar to, but more complicated than:
sphere{0,1000 interion{media...}}hollow texture{...}}
No need to use the union.
--
Alain
-------------------------------------------------
If you pick up a starving dog and make him prosperous, he will not bite you;
that is the principal difference between a dog and a man.
Mark Twain
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