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The following link is an excellent description of
the design and development of one of the Dec 1998
IRTC entries, "First Strike at Pearl" by
"N.B." and Glenn McCarter. The image is at :
image : http://www.irtc.org/ftp/pub/stills/1998-12-31/strike.jpg
text description : http://www.irtc.org/ftp/pub/stills/1998-12-31/strike.txt
details : http://www.geocities.com/SoHo/Workshop/9193/index.html
Since the round is currently open for voting, I will avoid publically
stating my opinions of the work with respect to the competition, but
it is highly worth checking out for its own merits.
Dan
--
http://www.flash.net/~djconnel/
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Dan Connelly wrote:
> The following link is an excellent description of
> the design and development of one of the Dec 1998
> IRTC entries, "First Strike at Pearl" by
> "N.B." and Glenn McCarter. The image is at :
>
> image : http://www.irtc.org/ftp/pub/stills/1998-12-31/strike.jpg
> text description : http://www.irtc.org/ftp/pub/stills/1998-12-31/strike.txt
> details : http://www.geocities.com/SoHo/Workshop/9193/index.html
>
> Since the round is currently open for voting, I will avoid publically
> stating my opinions of the work with respect to the competition, but
> it is highly worth checking out for its own merits.
>
> Dan
I too will avoid comment on the specifics of this scene which is
note worthy in and of itself but one thing concerns me about this
image and other recent image postings using the new media feature.
That concern is the grain structure that seems to be an inherent
artifact of the process. While not as pronounced in the smoke of
the above mentioned image, probably due to it's distance, it really
shows up often in many other images. I wonder if this is going to
be a fact of life with this feature or if there is a something that can
be done to reduce the particle size while maintaining the density
needed for realism.
Smoke paticles are very fine particulate matter and the reason it
appears to us as it does is primarily due to shear volume. Might this
grain artifact be a problem of image resolutions and screen capabilities
or am I just jumping the gun on this still evolving feature ?
I'm willing to entertain discussion on this but truthfully have as yet
not spent much time with it and am by no means a barometer of
it's potential.
--
Ken Tyler
tyl### [at] pacbell net
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It's really just a function of the sampling. If you recall the
particular look of atmosphere, it had a distinct banded look. Even
though it was way off, it tended to look smoother because it was so in
at least on direction. But that was just because it sampled at equal
lengths along the viewing ray. Using jitter gave it a look similiar to
media.
The grainyness is objectionable though. Something I've been thinking
about is that there must be some way to smooth media without taking
extra samples. I figure it should involve comparing pixels and trying
to balance them. I suppose a new keyword could let the user control
this by allowing the user to give a maximum intensity difference that
the pixels should be smoothed. The maximum for 24 bit images should be
1/255, but higher values would likely be specified. Perhaps the sampled
pixels could be grouped into fours and cached, then they could be
compared against each other. Then the intensities would be adjusted
until neighboring pixels don't vary by more than the specified amount.
I've heard that similiar techniques are used for stachastic renderers
for the same reason. There is a certain loss of accuracy, but it
doesn't require much extra time and results in more visually pleasing
images. If you take that image and draw a freehand mask around it in a
paint program, then apply a gaussian blur to the image, I bet the
results would be very nice.
comments/flames?
-Mike
Ken wrote:
> I too will avoid comment on the specifics of this scene which is
> note worthy in and of itself but one thing concerns me about this
> image and other recent image postings using the new media feature.
> That concern is the grain structure that seems to be an inherent
> artifact of the process. While not as pronounced in the smoke of
> the above mentioned image, probably due to it's distance, it really
> shows up often in many other images. I wonder if this is going to
> be a fact of life with this feature or if there is a something that can
> be done to reduce the particle size while maintaining the density
> needed for realism.
> Smoke paticles are very fine particulate matter and the reason it
> appears to us as it does is primarily due to shear volume. Might this
> grain artifact be a problem of image resolutions and screen capabilities
> or am I just jumping the gun on this still evolving feature ?
>
> I'm willing to entertain discussion on this but truthfully have as yet
> not spent much time with it and am by no means a barometer of
> it's potential.
>
> --
> Ken Tyler
>
> tyl### [at] pacbellnet
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Mike wrote:
> It's really just a function of the sampling. If you recall the
> particular look of atmosphere, it had a distinct banded look. Even
> though it was way off, it tended to look smoother because it was so in
> at least on direction. But that was just because it sampled at equal
> lengths along the viewing ray. Using jitter gave it a look similiar to
> media.
>
> The grainyness is objectionable though. Something I've been thinking
> about is that there must be some way to smooth media without taking
> extra samples. I figure it should involve comparing pixels and trying
> to balance them. I suppose a new keyword could let the user control
> this by allowing the user to give a maximum intensity difference that
> the pixels should be smoothed. The maximum for 24 bit images should be
> 1/255, but higher values would likely be specified. Perhaps the sampled
> pixels could be grouped into fours and cached, then they could be
> compared against each other. Then the intensities would be adjusted
> until neighboring pixels don't vary by more than the specified amount.
>
> I've heard that similiar techniques are used for stachastic renderers
> for the same reason. There is a certain loss of accuracy, but it
> doesn't require much extra time and results in more visually pleasing
> images. If you take that image and draw a freehand mask around it in a
> paint program, then apply a gaussian blur to the image, I bet the
> results would be very nice.
>
> comments/flames?
>
> -Mike
Your system date is off a day.
I was working with fog in a recent image after trying unsuccessfully
to get atmospheric media to work the way I wanted and thought
to myself on more than one occassion how now it would be to
be able to constrain the fog feature into a specific volume of space
like you can media. The particle size used in the fog function is
very nicely uniform in size and the density is controllable through
filtering and transmission values. A few enhancements and more
user control over that feature would make for great smoke,
clouds, and various other similar items that have no real substance.
The feasibibility of such an undertaking I no not but I can dream.
--
Ken Tyler
tyl### [at] pacbellnet
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Ken wrote in message <369### [at] pacbellnet>...
<snip>
> That concern is the grain structure that seems to be an inherent
>artifact of the process. While not as pronounced in the smoke of
>the above mentioned image, probably due to it's distance, it really
>shows up often in many other images. I wonder if this is going to
>be a fact of life with this feature or if there is a something that can
>be done to reduce the particle size while maintaining the density
>needed for realism.
<snip>
I've found increasing the intervals to around 30 smoothes the media quite
considerably, with little noticeable speed decrease (on my system anyway..).
Matt
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About Atmospheric banding... I had problems with that even though I set
sample VERY high... then I realized that since I was running my Desktop
at 16bit color, I was viewing a 24bit image, undithered at
16bits...Changing my Desktop to 32bit cleared up the banding. Just a
comment (it doesn't fix the media grain artifact, but I must believe
that this graininess can be used somehow..)
Steve
Mike wrote:
>
> It's really just a function of the sampling. If you recall the
> particular look of atmosphere, it had a distinct banded look. Even
> though it was way off, it tended to look smoother because it was so in
> at least on direction. But that was just because it sampled at equal
> lengths along the viewing ray. Using jitter gave it a look similiar to
> media.
>
> The grainyness is objectionable though. Something I've been thinking
> about is that there must be some way to smooth media without taking
> extra samples. I figure it should involve comparing pixels and trying
> to balance them. I suppose a new keyword could let the user control
> this by allowing the user to give a maximum intensity difference that
> the pixels should be smoothed. The maximum for 24 bit images should be
> 1/255, but higher values would likely be specified. Perhaps the sampled
> pixels could be grouped into fours and cached, then they could be
> compared against each other. Then the intensities would be adjusted
> until neighboring pixels don't vary by more than the specified amount.
>
> I've heard that similiar techniques are used for stachastic renderers
> for the same reason. There is a certain loss of accuracy, but it
> doesn't require much extra time and results in more visually pleasing
> images. If you take that image and draw a freehand mask around it in a
> paint program, then apply a gaussian blur to the image, I bet the
> results would be very nice.
>
> comments/flames?
>
> -Mike
>
> Ken wrote:
>
> > I too will avoid comment on the specifics of this scene which is
> > note worthy in and of itself but one thing concerns me about this
> > image and other recent image postings using the new media feature.
> > That concern is the grain structure that seems to be an inherent
> > artifact of the process. While not as pronounced in the smoke of
> > the above mentioned image, probably due to it's distance, it really
> > shows up often in many other images. I wonder if this is going to
> > be a fact of life with this feature or if there is a something that can
> > be done to reduce the particle size while maintaining the density
> > needed for realism.
> > Smoke paticles are very fine particulate matter and the reason it
> > appears to us as it does is primarily due to shear volume. Might this
> > grain artifact be a problem of image resolutions and screen capabilities
> > or am I just jumping the gun on this still evolving feature ?
> >
> > I'm willing to entertain discussion on this but truthfully have as yet
> > not spent much time with it and am by no means a barometer of
> > it's potential.
> >
> > --
> > Ken Tyler
> >
> > tyl### [at] pacbellnet
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Ken wrote:
> Your system date is off a day.
Pardon my French but MotherF*^$er!!! I've had several people tell me it
was off and after several missed attempts I'm sure I got it right now.
I can't for the life of me understand why my message was listed as being
posted on Sunday. I'm looking at my system date and time now and it
says Monday, January 4th, 1999, 9:14...crap, it says AM! ARGGGGGGGGH!!!!
Um, I got it fixed now. Blood pressure dropping...sanity returning...
> I was working with fog in a recent image after trying unsuccessfully
> to get atmospheric media to work the way I wanted and thought
> to myself on more than one occassion how now it would be to
> be able to constrain the fog feature into a specific volume of space
> like you can media. The particle size used in the fog function is
> very nicely uniform in size and the density is controllable through
> filtering and transmission values. A few enhancements and more
> user control over that feature would make for great smoke,
> clouds, and various other similar items that have no real substance.
> The feasibibility of such an undertaking I no not but I can dream.
Actually, you can put fog in an object. It fun to do too cause it's
fast. The trick is to make an object and put some fog in it, then use
inverse. Now the inside is outside and the outside is inside. :)
-Mike
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Stephen Lavedas wrote:
>
> About Atmospheric banding... I had problems with that even though I set
> sample VERY high... then I realized that since I was running my Desktop
> at 16bit color, I was viewing a 24bit image, undithered at
> 16bits...Changing my Desktop to 32bit cleared up the banding. Just a
> comment (it doesn't fix the media grain artifact, but I must believe
> that this graininess can be used somehow..)
The problem with the image in question (FSaP) is clearly not color
discritization....
The problem is the simple Monte-Carlo technique used by POV. Each pixel
has the integral calculated independently from its neighboring
pixels. This is wasting information. More sophisticated Monte-Carlo
techniques can be used, with introduction of potentially considerable
complexity, which make use of the generally smoothly-varying nature
of the media fields.
The problem reminds me of the one in semiconductor device processing,
where Monte-Carlo is being used to predict the distribution of ions
which result from the bombardment of semiconductor device surfaces
with charged dopants. Some excellent results were demonstrated
at the latest International Electron Device Conference in San Francisco
of the use of some clever but relatively simple techniques to get
more out of each randomly sampled ion event. For example, one can
do "particle splitting" in which more than one particle shares part of a path,
but then part way through is split into multiple particles to generate
different random paths. But I digress....
The improvement of the interior methods would make an excellent
subject for a patch.
Dan
--
http://www.flash.net/~djconnel/
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Hey guys, I kind of liked the image :) at least until reading all these
techno-notes about it.
A great picture is bound to get more scrutiny than others though.
And I have a thought too. Looks like quite a bit of turbulence used,
depending on how it was applied, that can cause some level of graininess
too. The artist might have even preferred the look of it as is anyhow.
And if emission or absorption is used the crandy nature increases
drastically over pure scatter and density alone, from what I've seen. Be
willing to bet absortion, at least, was used.
The flaming parts were noticably ephemeral looking to me and caught my
attention more than the sooty smoke did. A tighter, torrent of flames
would have looked nice.
Want to say, btw, loved the pictures detail and "overall" look.
Dan Connelly wrote:
>
> Stephen Lavedas wrote:
> >
> > About Atmospheric banding... I had problems with that even though I set
> > sample VERY high... then I realized that since I was running my Desktop
> > at 16bit color, I was viewing a 24bit image, undithered at
> > 16bits...Changing my Desktop to 32bit cleared up the banding. Just a
> > comment (it doesn't fix the media grain artifact, but I must believe
> > that this graininess can be used somehow..)
>
> The problem with the image in question (FSaP) is clearly not color
> discritization....
>
> The problem is the simple Monte-Carlo technique used by POV. Each pixel
> has the integral calculated independently from its neighboring
> pixels. This is wasting information. More sophisticated Monte-Carlo
> techniques can be used, with introduction of potentially considerable
> complexity, which make use of the generally smoothly-varying nature
> of the media fields.
>
> The problem reminds me of the one in semiconductor device processing,
> where Monte-Carlo is being used to predict the distribution of ions
> which result from the bombardment of semiconductor device surfaces
> with charged dopants. Some excellent results were demonstrated
> at the latest International Electron Device Conference in San Francisco
> of the use of some clever but relatively simple techniques to get
> more out of each randomly sampled ion event. For example, one can
> do "particle splitting" in which more than one particle shares part of a path,
> but then part way through is split into multiple particles to generate
> different random paths. But I digress....
>
> The improvement of the interior methods would make an excellent
> subject for a patch.
>
> Dan
>
> --
> http://www.flash.net/~djconnel/
--
omniVERSE: beyond the universe
http://members.aol.com/inversez/POVring.htm
=Bob
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Bob Hughes wrote:
>
> Hey guys, I kind of liked the image :) at least until reading all these
> techno-notes about it.
>
Actually I believe everybody has done a great job of sticking
to the subject of the media grain problems and have avoided the
critiqueing of the image quite ethicaly. That is until ...
--
Ken Tyler
tyl### [at] pacbellnet
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