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With the camera and light above the following boxes, BoxA shows up as white
media, which is what I expected, but BoxB shows up as black - why is this?
After all, if you are looking down at a cloud from an airplane, beyond a
certain point the actual physical thickness of the cloud is not
particularily significant (is it?).
#declare BoxA = // nice 'n' white
box
{
<-10000, -1, -10000>
< 10000, 0, 10000>
pigment{rgbf<1,1,1,1>}
hollow on
interior{media{Plain_White_Scattering_Media}}
}
#declare BoxB = // completely black
box
{
<-10000, -10000, -10000>
< 10000, 0, 10000>
pigment{rgbf<1,1,1,1>}
hollow on
interior{media{Plain_White_Scattering_Media}}
}
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Tom Melly wrote:
>
> With the camera and light above the following boxes, BoxA shows up as white
> media, which is what I expected, but BoxB shows up as black - why is this?
> After all, if you are looking down at a cloud from an airplane, beyond a
> certain point the actual physical thickness of the cloud is not
> particularily significant (is it?).
Since no one else appears interested in answering your question, and I have
no informed answer for you myself, I will simply guess that the thicker
media container in example 2 will require a greater number of samples to
get similar results.
You didn't help much by not telling us what "Plain_White_Scattering_Media"
is either.
--
Ken Tyler - 1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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Hm. Isn't that making a shadow then? If there's a light above the thinner
white media box then there should be a shadow of that media and the other also.
And then there's light_source 'media attenuation'... But like Ken said you
didn't say what the media statement has in it so it's tough to speculate on what
it's doing in the first place.
Bob
"Tom Melly" <tom### [at] tomandlu force9couk> wrote in message
news:38ce75e7@news.povray.org...
| With the camera and light above the following boxes, BoxA shows up as white
| media, which is what I expected, but BoxB shows up as black - why is this?
| After all, if you are looking down at a cloud from an airplane, beyond a
| certain point the actual physical thickness of the cloud is not
| particularily significant (is it?).
|
| #declare BoxA = // nice 'n' white
| box
| {
| <-10000, -1, -10000>
| < 10000, 0, 10000>
| pigment{rgbf<1,1,1,1>}
| hollow on
| interior{media{Plain_White_Scattering_Media}}
| }
|
| #declare BoxB = // completely black
| box
| {
| <-10000, -10000, -10000>
| < 10000, 0, 10000>
| pigment{rgbf<1,1,1,1>}
| hollow on
| interior{media{Plain_White_Scattering_Media}}
| }
|
|
|
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Sorry for lack of clarity - have reposted with full code to text.scene-files
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I tried it out and although I don't fully know the reasoning behind it I found
putting extinction .0025 into the 'scattering' statement fixes it. The logic
seems right if there were 'media_attenuation on' in the light but I tried adding
that in as well with it both on and off, neither way makes a difference.
Check it out using 0.0033 for the extinction and it's interesting. My guess is
the missing link to 'density', it acts as though there is a 'density {rgb 1}'
present I believe and if approximately density {rgb .00025} (or lower) is used
then it corrects it (no need for extinction then either).
Bob
"Tom Melly" <tom### [at] tomandluforce9couk> wrote in message
news:38cfc981$1@news.povray.org...
| Sorry for lack of clarity - have reposted with full code to text.scene-files
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I experimented breifly with the scene and found that the thicker BoxB is, the
more "spotted" with dark spots it gets, so by the time it gets a deep as you
have it, it has so many darker spots that it appears to be black with white
spots.
You can increase the intervals and samples of the media, but the cost in
rendering time is enormous. I don't recommend it, but it does increase the
white levels of the media.
Josh
Tom Melly wrote:
> With the camera and light above the following boxes, BoxA shows up as white
> media, which is what I expected, but BoxB shows up as black - why is this?
> After all, if you are looking down at a cloud from an airplane, beyond a
> certain point the actual physical thickness of the cloud is not
> particularily significant (is it?).
>
> #declare BoxA = // nice 'n' white
> box
> {
> <-10000, -1, -10000>
> < 10000, 0, 10000>
> pigment{rgbf<1,1,1,1>}
> hollow on
> interior{media{Plain_White_Scattering_Media}}
> }
>
> #declare BoxB = // completely black
> box
> {
> <-10000, -10000, -10000>
> < 10000, 0, 10000>
> pigment{rgbf<1,1,1,1>}
> hollow on
> interior{media{Plain_White_Scattering_Media}}
> }
--
Josh English
eng### [at] spiritonecom
"May your hopes, dreams, and plans not be destroyed by a few zeros."
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> I experimented breifly with the scene and found that the thicker BoxB is,
the
> more "spotted" with dark spots it gets, so by the time it gets a deep as
you
> have it, it has so many darker spots that it appears to be black with
white
> spots.
>
Sounds right - I first ran into this using media with a hollow plane, then a
deep box before finally in a "one last try" mood using a thinner box.
> You can increase the intervals and samples of the media, but the cost in
> rendering time is enormous. I don't recommend it, but it does increase the
> white levels of the media.
>
Thanks for the suggestion, I'll try it out.
However, I suspect that this might just result in a less spots, more black -
I only say this as this is what I get in the MegaPOV which seems less prone
to "spotiness" in medias.
--
Tom Melly
tom### [at] tomandluforce9couk
http://www.tomandlu.force9.co.uk
Josh English <eng### [at] spiritonecom> wrote in message
news:38CFDD95.5A7EBD44@spiritone.com...
> I experimented breifly with the scene and found that the thicker BoxB is,
the
> more "spotted" with dark spots it gets, so by the time it gets a deep as
you
> have it, it has so many darker spots that it appears to be black with
white
> spots.
>
> You can increase the intervals and samples of the media, but the cost in
> rendering time is enormous. I don't recommend it, but it does increase the
> white levels of the media.
>
> Josh
>
> Tom Melly wrote:
>
> > With the camera and light above the following boxes, BoxA shows up as
white
> > media, which is what I expected, but BoxB shows up as black - why is
this?
> > After all, if you are looking down at a cloud from an airplane, beyond a
> > certain point the actual physical thickness of the cloud is not
> > particularily significant (is it?).
> >
> > #declare BoxA = // nice 'n' white
> > box
> > {
> > <-10000, -1, -10000>
> > < 10000, 0, 10000>
> > pigment{rgbf<1,1,1,1>}
> > hollow on
> > interior{media{Plain_White_Scattering_Media}}
> > }
> >
> > #declare BoxB = // completely black
> > box
> > {
> > <-10000, -10000, -10000>
> > < 10000, 0, 10000>
> > pigment{rgbf<1,1,1,1>}
> > hollow on
> > interior{media{Plain_White_Scattering_Media}}
> > }
>
> --
> Josh English
> eng### [at] spiritonecom
> "May your hopes, dreams, and plans not be destroyed by a few zeros."
>
>
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Tom Melly wrote:
>
> With the camera and light above the following boxes, BoxA shows up as white
> media, which is what I expected, but BoxB shows up as black - why is this?
> After all, if you are looking down at a cloud from an airplane, beyond a
> certain point the actual physical thickness of the cloud is not
> particularily significant (is it?).
Irel arj Zbenl/CBI-Enl MEDIA urer jvgu n ynetr urnqnpur samples gelvat
svther intervals pbeerpg yvtugvat ratio sbe fbzr pbzchgre blob tencuvp.
V nz hollow vzorpvyr gb inverse jvgu fb Voxel gnyxrq gb fbzr cebsrffvb
qrfvtaref naked gurls jrr gnyxvat nobhg gur x*3 yvtug zrgubq sbe yvtug
fprar.
And that is all I can add to this.
--
Ken Tyler - 1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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Many thanks - I'll play with those settings. I must confess that media still
mystifies me - as soon as I seem to be able to make a model in my head of
what it does, it goes and bites me in the arse. Why, for example, should the
extinction value be so significant - particularily as the docs advise that
the default is the most accurate representation? IMHO If x units thickness
of media show as white, then so should x+y (when the media is viewed from
the lighted side). Is this an inaccuracy? (the thick media showing as
black) - if so why does megapov compound the error?
--
Tom Melly
tom### [at] tomandluforce9couk
http://www.tomandlu.force9.co.uk
Bob Hughes <omn### [at] hotmailcom?subject=PoV-News:> wrote in message
news:38cfdd64@news.povray.org...
> I tried it out and although I don't fully know the reasoning behind it I
found
> putting extinction .0025 into the 'scattering' statement fixes it. The
logic
> seems right if there were 'media_attenuation on' in the light but I tried
adding
> that in as well with it both on and off, neither way makes a difference.
> Check it out using 0.0033 for the extinction and it's interesting. My
guess is
> the missing link to 'density', it acts as though there is a 'density {rgb
1}'
> present I believe and if approximately density {rgb .00025} (or lower)
is used
> then it corrects it (no need for extinction then either).
>
> Bob
>
> "Tom Melly" <tom### [at] tomandluforce9couk> wrote in message
> news:38cfc981$1@news.povray.org...
> | Sorry for lack of clarity - have reposted with full code to
text.scene-files
>
>
>
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On Wed, 15 Mar 2000 12:14:06 -0800, Ken wrote:
>And that is all I can add to this.
What is that, some kind of Markov Chain/ROT13 thing? It's truly
beautiful; I haven't hit esc-R that much for one post in a long time.
--
These are my opinions. I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html
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Like I was feebly trying to say before, I think it's a hidden coupling with
density being a default of 1 (maybe?) even when not specified at all. That's
just a guess of course but it seems to fit.
I believe the most correct way to use scattering then is to use a much lower
color value when the volume is greater and vice versa.
Try this out: multiply White by 10000 when you use the BoxA. The resulting
render will look much the same as your "wrong" BoxB render. Divide White by
10000 and use BoxB, it will be all white. It's still just a volume/scattering
relationship after all but I still think an implied density {rgb 1} is in there
whether used or not. extinction is probably a part of it all for that very
reason but I'm not the one to say that's absolutely so.
Bob
"Tom Melly" <tom### [at] tomandluf9couk> wrote in message
news:38cfeeff@news.povray.org...
| Many thanks - I'll play with those settings. I must confess that media still
| mystifies me - as soon as I seem to be able to make a model in my head of
| what it does, it goes and bites me in the arse. Why, for example, should the
| extinction value be so significant - particularily as the docs advise that
| the default is the most accurate representation? IMHO If x units thickness
| of media show as white, then so should x+y (when the media is viewed from
| the lighted side). Is this an inaccuracy? (the thick media showing as
| black) - if so why does megapov compound the error?
|
| --
| Tom Melly
| tom### [at] tomandluforce9couk
| http://www.tomandlu.force9.co.uk
|
| Bob Hughes <omn### [at] hotmailcom?subject=PoV-News:> wrote in message
| news:38cfdd64@news.povray.org...
| > I tried it out and although I don't fully know the reasoning behind it I
| found
| > putting extinction .0025 into the 'scattering' statement fixes it. The
| logic
| > seems right if there were 'media_attenuation on' in the light but I tried
| adding
| > that in as well with it both on and off, neither way makes a difference.
| > Check it out using 0.0033 for the extinction and it's interesting. My
| guess is
| > the missing link to 'density', it acts as though there is a 'density {rgb
| 1}'
| > present I believe and if approximately density {rgb .00025} (or lower)
| is used
| > then it corrects it (no need for extinction then either).
| >
| > Bob
| >
| > "Tom Melly" <tom### [at] tomandluforce9couk> wrote in message
| > news:38cfc981$1@news.povray.org...
| > | Sorry for lack of clarity - have reposted with full code to
| text.scene-files
| >
| >
| >
|
|
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On Wed, 15 Mar 2000 12:14:06 -0800, Ken <tyl### [at] pacbellnet> wrote:
>Irel arj Zbenl/CBI-Enl MEDIA urer jvgu n ynetr urnqnpur samples gelvat
>svther intervals pbeerpg yvtugvat ratio sbe fbzr pbzchgre blob tencuvp.
>V nz hollow vzorpvyr gb inverse jvgu fb Voxel gnyxrq gb fbzr cebsrffvb
>qrfvtaref naked gurls jrr gnyxvat nobhg gur x*3 yvtug zrgubq sbe yvtug
>fprar.
>
>And that is all I can add to this.
Ken, something wrong has gone with your speech synthesizer. You seem
to have somehow linked the random-POV-geek-slang-generator to the AI
encoder for even after I decoded it it made no sense at all (except
the gurls part :) )
Peter Popov
pet### [at] usanet
ICQ: 15002700
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Ken <tyl### [at] pacbellnet> wrote in message
news:38CFEF0E.F1F72277@pacbell.net...
>
>.....
> fprar.
>
> And that is all I can add to this.
>
That works for me.
P.S. Sorry for the lack of snipping in my previous follow-ups - I accidently
pressed some send shortcut before I had a chance.
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Ron Parker wrote:
> Jung vf gung, fbzr xvaq bs Znexbi Punva/EBG13 guvat?
Yes.
> Vg'f gehyl ornhgvshy; V unira'g uvg rfp-E gung zhpu sbe bar cbfg va n ybat gvzr.
What does esc-R do ?
--
Ken Tyler - 1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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On Wed, 15 Mar 2000 12:14:06 -0800 Ken <tyl### [at] pacbellnet> wrote:
>Irel arj Zbenl/CBI-Enl MEDIA urer jvgu n ynetr urnqnpur samples gelvat
>svther intervals pbeerpg yvtugvat ratio sbe fbzr pbzchgre blob tencuvp.
>V nz hollow vzorpvyr gb inverse jvgu fb Voxel gnyxrq gb fbzr cebsrffvb
>qrfvtaref naked gurls jrr gnyxvat nobhg gur x*3 yvtug zrgubq sbe yvtug
>fprar.
MEDIA samples intervals ratio blob hollow inverse naked gurls...
Ken, you neglected to include a .url where we could see some examples.
Am I correct in assuming that you ran this post through the
Transbibitiser? Is that Polish?
--
Alan - ako### [at] povrayorg - a k o n g <at> p o v r a y <dot> o r g
http://www.povray.org - Home of the Persistence of Vision Ray Tracer
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Alan Kong wrote:
>
> On Wed, 15 Mar 2000 12:14:06 -0800 Ken <tyl### [at] pacbellnet> wrote:
>
> >Irel arj Zbenl/CBI-Enl MEDIA urer jvgu n ynetr urnqnpur samples gelvat
> >svther intervals pbeerpg yvtugvat ratio sbe fbzr pbzchgre blob tencuvp.
> >V nz hollow vzorpvyr gb inverse jvgu fb Voxel gnyxrq gb fbzr cebsrffvb
> >qrfvtaref naked gurls jrr gnyxvat nobhg gur x*3 yvtug zrgubq sbe yvtug
> >fprar.
>
> MEDIA samples intervals ratio blob hollow inverse naked gurls...
You missed Voxel and x*3.
> Ken, you neglected to include a .url where we could see some examples.
www.povsmut.com
> Am I correct in assuming that you ran this post through the
> Transbibitiser?
The ROT-13 Dual Overhead Turbo Transbibitiser Mark IV Limited Edition.
> Is that Polish?
Yeski.
--
Ken Tyler - 1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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On Wed, 15 Mar 2000 15:28:04 -0800, Ken wrote:
>What does esc-R do ?
It rot-13's a post in slrn, of course.
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On Wed, 15 Mar 2000 15:44:27 -0800, Alan Kong
<ako### [at] povrayNO-SPAMorg> wrote:
> MEDIA samples intervals ratio blob hollow inverse naked gurls...
I prefer straight girls, thank you. Blobs I don't mind but they better
not be hollow behind the ears.
Peter Popov
pet### [at] usanet
ICQ: 15002700
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BTW very good reply to this in the pov.text.scene-files from J.Berger that
gives a good picture of why media behaves in this way. Haven't played with
it yet, but it makes a lot of sense IMHO.
--
Tom Melly
tom### [at] tomandluforce9couk
http://www.tomandlu.force9.co.uk
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On Thu, 16 Mar 2000 23:08:37 +0200, Peter Popov wrote:
>On Wed, 15 Mar 2000 15:44:27 -0800, Alan Kong
><ako### [at] povrayNO-SPAMorg> wrote:
>
>> MEDIA samples intervals ratio blob hollow inverse naked gurls...
>
>I prefer straight girls, thank you. Blobs I don't mind but they better
>not be hollow behind the ears.
But there's somthing very attractive about a woman who has to close
down all other brain functions in order to recite the days of the week
in reverse order.
--
Cheers
Steve email mailto:sjl### [at] ndirectcouk
%HAV-A-NICEDAY Error not enough coffee 0 pps.
web http://www.ndirect.co.uk/~sjlen/
or http://start.at/zero-pps
3:34am up 2 days, 1:00, 5 users, load average: 1.15, 1.21, 1.18
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http://paul.merton.ox.ac.uk/misc/rules-woman.html
http://www.cee.hw.ac.uk/~pjbk/humour/goodwife.html
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