No, the integration scheme is *very* important.
My background is in physically based modeling
in computer animation, so here is what I know:
The integration scheme can have such a strong
influence on the stability of the system that
it can mean going from an integration timestep
of a microsecond to a hundredth of a second.
That's a speedup of 10,000. Generally, the
finer the spatial resolution of you simulation
(how fine your cloth mesh or fluid volume is),
the faster a timestep you need.
The brief description of the book cites the
Runga-Kutta method as a preferred technique
over basic Euler integration. The former
is a fourth-order method, the latter a
first-order method. Three orders of magnitude
is nothing to laugh at.
The big breakthrough in cloth deformations came
because Witkin and Kass figured out how to
simulate cloth with a large timestep (they use
implicit integration techniques). Jos Stam
did some nice work with real-time fluids that
relied on a semi-Lagrangian integration scheme
with a vorticity term to undo the artifical dissipation caused by the coarse numerical
simulation.
Actually, the ICT hired Paul Debevec, one of the most prolific young researchers in using real-world data in graphics. Some of his work involves capturing the reflectance properties of skin and rendering the skin with novel geometry and novel lighting. That's a little better than a Quake skin.;)
There's a lot more to the army now than just shooting things up. Peacekeeping missions involve communications, logistics,etc. See here for a sample script (peace-keeping in the Balkans) that they used.
Google has a mechanism that allows people to
remove content from the cache. If the govt
wished to, they could get pages removed from
google's cache. EFF lists at least one govt
page (map of nuclear reactors in US) that is
not cached in google anymore:
EFF article
For more information on google's cache removal policy,
look here.
A year and a half ago I moved from Atlanta to Seattle and shipped seven boxes containing all of my stuff. Each box was packed very well, had arrows indicating up, displayed the weights of the boxes (up to 90 pounds for one of the boxes), and was insured apporpriately. Six of the seven boxes arrived with the contents perfectly intact, including my cello. The seventh box contained my CDs and looked like it had gotten dropped in the ocean. UPS gave me promptly the $500 I insured the box for, and I also was able to clean up most of the CDs.
an American student got released from Russian
prisons after serving part of a questionable
conviction.
CNN story here
Maybe the Russians can argue now, "We freed your
guy; how about you free ours?"
Re:Random bits that are in Pi somewhere
on
Share The Pi!
·
· Score: 1
This is the claim I would make:
For any finite substring of e, it exists
somewhere in pi. For any finite substring of
pi, it exists somewhere in e (assuming e is
normal).
Now let's have fun: For any finite substring s
of e, there exists a finite substring t of e
such that the t is is the first |t| digits of
pi, ending in s.
We can recurse like this arbitrarily deep
(i.e. if i can recurse to depth k, i can
recurse to depth k+1).
Re:What about the length between the messages?
on
Share The Pi!
·
· Score: 3
A specific string of k bits long will on average occur every 2^k bits of a random bitstream.
(For example, it will on average take about
1024 coin tosses to get 10 heads in a row.)[0]
The reasoning I have in mind for this relies
on the fact that coin tosses are independent
events. The digits of pi are certainly not independent random events because we can calculate
them. However, because of normality behaves macroscopically much like independent events,
k precise bits will occur on average
every 2^k bits of pi. I imagine the actual
proof is highly nontrivial, but handwavy entropy
arguments convince me that this is true.
[0] As an interesting sidenote, many of the "streaks" in sports coincide roughly with the
streaks that probability dictates. Baseball hitting streaks aren't necessarily because the
hitter is in the zone... they may be because
probabalistically, they are due to hit in 30
games in a row if their average is.320 and they
play 1000 games (made-up numbers).
Re:Craziness with transcendental and imaginary #s
on
Share The Pi!
·
· Score: 1
Taylor series are used to approximate smooth
functions by polynomials. The coefficients
for the Taylor series are derived from the
nth derivatives. See any calculus book for more.
The Taylor series for e^u is:
1+u+u^2/2!+u^3/3!+u^4/4!+u^5/5!+...
The Taylor series for cos u is:
1-u^2/2!+u^4/4!-u^6/6!+...
The Taylor series for sin u is:
u-u^3/3!+u^5/5!-u^7/7!+...
Now let's look at u=ix for e^u:
e^ix = 1+ix-x^2/2!-ix^3/3!+x^4/4!+ix^5/5!-x^6/6!...
=cos x + i sin x
A lot of people seem to be confused on why we're interested in nonphotorealistic rendering. It is not because we want to reproduce exactly Van Goghs
or Monets or Dalis. Surely one could argue convincingly that it would require solving the AI
problem.
Instead NPR is about an alternative way to present
content efficiently. Technical sketches are easier to understand than photographs of the same part. We might want an impressionistic style to an animation to capture a dreamy mood. We might want cartoon physics to do Roadrunner/Coyote stuff. A person can understand and feel a grossly
simple cartoon but feel disturbed by a photorealistic rendering with imperfect shadows.
There are other good reasons for NPR, but I'm off to an ultimate game...
You notice diffraction and interference a lot more
than you think.
Look at a compact disk.
Look at the sun through your eyelashes.
One way to reproduce those
effects would be to model the microgeometry. However such a scheme would require way too much time and would suffer from numerical precision problems. Instead researchers construct analytical methods or model the macroscopic statistics of the microgeometry.
With regards to the original QED poster, researchers recently have looked at dispersion, fluorescence, phosphorescence, Rayleigh and Mie scattering, subsurface scattering, hair, skin, diffraction, wet objects, iridescence, etc.
For some of these effects, a clever shader can
reproduce the rough characteristics of the effect. Otherwise some subset of the physics is modeled.
For more info, check out recent SIGGRAPHs, Euro. Workshops on Rendering, and Glassner's Principles of Digital Image Synthesis.
And check out this SIGGRAPH for how to render skim milk vs 2% milk vs whole milk:)
My freshman year in college (1996) was pretty
much first year of prevalent online gaming.
We played Quake, we saw cheaters and got mad at
them, and we cheated too.
Quake was available on the SGIs then. On the
SGIs, it was trivial to turn the polygon rendering into wireframe mode (probably equivalent to what
this driver is claiming to do). My guess is someone might also be able to hack up a DLL for GL
that renders polygons as wireframes and have any
game load up the hacked DLL instead. Not only
has ASUS's "cheat" been around for years, but I
also contend that someone can write one for the
PC that will work with any graphics card.
Now onto cheating. Some of the ways we cheated
(would be considered cheating under most people's
definitions):
1) changing the invisible-person model to visible
2) changing the person model to emit a really huge
glow (so can be seen from behind walls)
3) editing holes into walls
4) using cheat modes that no one else knew about
5) hacking the quake executable so that the server
could not send commands to the client (e.g. renaming color to dolor so in capture-the-flag,
you could be colored blue but be on the red team)
6) using bots (I hacked up the StoogeBot to remove the SBot name and to disable the "No Bots" kick off -- it was actually a nontrivial hack)
Believe it or not, when we competed in clan matches, we did not use any of the above. We
reserved the above as an added toy for when
we were in the mood for something different
(and it was very much a game of who could figure
out how to cheat the most).
There were also other things we did that could be
considered cheating because they likewise gave
us unfair advantages (but I am guessing that most
of you will not consider them cheating):
1) Talking to each other over the phone on headsets
2) Having a tool sit next to the quake player to
time quad, RL, and shout out "5 sec till quad," etc.
3) Remembering spawning-point orders
4) Using our 3l33t mice to shoot rockets down
for splash damage instead of being a dumb keyboarder and going for the direct hit
5) When running into a room, shooting rockets blindly into known camping spots.
When we played other clans, we did not cheat,
and we did not get accused of cheating.
When we played against random people online,
we would constantly be accused of cheating.
"You always have quad! Stop camping quad!"
"Actually I showed up at quad 5 sec ago to
kill the camper waiting there.""Bullshit! You must be cheating!"
I got so sick and tired of being called a cheater
while playing legitimately that I did an experiment:
I played using the bot and the name "Yo Mama."
Almost immediately I got called a cheater.
Another time, I played using the bot but the name
"Thresh" (the best Quake player then). Funny,
I never got called a cheater.
The moral of the story is that people get annoyed when they play against a suspected cheater (because only someone with better skillz should be able to beat them -- wouldn't want to shatter that ego) and when a good player playing legitimately is suspected of cheating (because that player wants everyone to know that his skillz are better than theirs -- wouldn't want to shatter that ego).
No matter what game designers try to do, people will always find a way to cheat. It will not always be easy to pick out cheaters from non-cheaters. So take all your playing with a grain of salt and don't let it get to your ego.
Gaming should be a fun stress reliever, not a stress giver.
Peer review can be plenty effective and
nearly[0] immune to bias when the reviews are
double-blind: the reviewers do not know the
authors, and the authors do not know the
reviewers. SIGGRAPH, the premiere graphics
conference (and perhaps even more prestigious
than the best graphics journals around[1]),
uses a double-blind system.
[0] Sometimes the reviewer can figure out the
author based on paper content and writing
style. Other times, humorous things happen,
such as the reviewer criticizing a paper
written by author X for not citing previous
work by author X.
[1] Unfortunately some old and wrinkled Board
of Regents folk who grant tenure still think
journals are better.
Slashdot Mirror
No, the integration scheme is *very* important.
My background is in physically based modeling
in computer animation, so here is what I know:
The integration scheme can have such a strong
influence on the stability of the system that
it can mean going from an integration timestep
of a microsecond to a hundredth of a second.
That's a speedup of 10,000. Generally, the
finer the spatial resolution of you simulation
(how fine your cloth mesh or fluid volume is),
the faster a timestep you need.
The brief description of the book cites the
Runga-Kutta method as a preferred technique
over basic Euler integration. The former
is a fourth-order method, the latter a
first-order method. Three orders of magnitude
is nothing to laugh at.
The big breakthrough in cloth deformations came
because Witkin and Kass figured out how to
simulate cloth with a large timestep (they use
implicit integration techniques). Jos Stam
did some nice work with real-time fluids that
relied on a semi-Lagrangian integration scheme
with a vorticity term to undo the artifical dissipation caused by the coarse numerical
simulation.
Actually, the ICT hired Paul Debevec, one of the most prolific young researchers in using real-world data in graphics. Some of his work involves capturing the reflectance properties of skin and rendering the skin with novel geometry and novel lighting. That's a little better than a Quake skin. ;)
There's a lot more to the army now than just shooting things up. Peacekeeping missions involve communications, logistics,etc. See here for a sample script (peace-keeping in the Balkans) that they used.
For more information on google's cache removal policy, look here.
A year and a half ago I moved from Atlanta to Seattle and shipped seven boxes containing all of my stuff. Each box was packed very well, had arrows indicating up, displayed the weights of the boxes (up to 90 pounds for one of the boxes), and was insured apporpriately. Six of the seven boxes arrived with the contents perfectly intact, including my cello. The seventh box contained my CDs and looked like it had gotten dropped in the ocean. UPS gave me promptly the $500 I insured the box for, and I also was able to clean up most of the CDs.
an American student got released from Russian prisons after serving part of a questionable conviction.
CNN story here
Maybe the Russians can argue now, "We freed your guy; how about you free ours?"
This is the claim I would make:
For any finite substring of e, it exists somewhere in pi. For any finite substring of pi, it exists somewhere in e (assuming e is normal).
Now let's have fun: For any finite substring s of e, there exists a finite substring t of e such that the t is is the first |t| digits of pi, ending in s.
We can recurse like this arbitrarily deep (i.e. if i can recurse to depth k, i can recurse to depth k+1).
A specific string of k bits long will on average occur every 2^k bits of a random bitstream. (For example, it will on average take about 1024 coin tosses to get 10 heads in a row.)[0] The reasoning I have in mind for this relies on the fact that coin tosses are independent events. The digits of pi are certainly not independent random events because we can calculate them. However, because of normality behaves macroscopically much like independent events, k precise bits will occur on average every 2^k bits of pi. I imagine the actual proof is highly nontrivial, but handwavy entropy arguments convince me that this is true.
.320 and they
play 1000 games (made-up numbers).
[0] As an interesting sidenote, many of the "streaks" in sports coincide roughly with the streaks that probability dictates. Baseball hitting streaks aren't necessarily because the hitter is in the zone... they may be because probabalistically, they are due to hit in 30 games in a row if their average is
Taylor series are used to approximate smooth functions by polynomials. The coefficients for the Taylor series are derived from the nth derivatives. See any calculus book for more.
The Taylor series for e^u is:
1+u+u^2/2!+u^3/3!+u^4/4!+u^5/5!+...
The Taylor series for cos u is:
1-u^2/2!+u^4/4!-u^6/6!+...
The Taylor series for sin u is:
u-u^3/3!+u^5/5!-u^7/7!+...
Now let's look at u=ix for e^u:
e^ix = 1+ix-x^2/2!-ix^3/3!+x^4/4!+ix^5/5!-x^6/6!...
=cos x + i sin x
Now just plug in x=pi to get e^(pi i)=-1.
Instead NPR is about an alternative way to present content efficiently. Technical sketches are easier to understand than photographs of the same part. We might want an impressionistic style to an animation to capture a dreamy mood. We might want cartoon physics to do Roadrunner/Coyote stuff. A person can understand and feel a grossly simple cartoon but feel disturbed by a photorealistic rendering with imperfect shadows. There are other good reasons for NPR, but I'm off to an ultimate game...
Look at a compact disk.
Look at the sun through your eyelashes.
One way to reproduce those effects would be to model the microgeometry. However such a scheme would require way too much time and would suffer from numerical precision problems. Instead researchers construct analytical methods or model the macroscopic statistics of the microgeometry.
With regards to the original QED poster, researchers recently have looked at dispersion, fluorescence, phosphorescence, Rayleigh and Mie scattering, subsurface scattering, hair, skin, diffraction, wet objects, iridescence, etc. For some of these effects, a clever shader can reproduce the rough characteristics of the effect. Otherwise some subset of the physics is modeled.
For more info, check out recent SIGGRAPHs, Euro. Workshops on Rendering, and Glassner's Principles of Digital Image Synthesis.
And check out this SIGGRAPH for how to render skim milk vs 2% milk vs whole milk :)
My freshman year in college (1996) was pretty much first year of prevalent online gaming. We played Quake, we saw cheaters and got mad at them, and we cheated too.
Quake was available on the SGIs then. On the SGIs, it was trivial to turn the polygon rendering into wireframe mode (probably equivalent to what this driver is claiming to do). My guess is someone might also be able to hack up a DLL for GL that renders polygons as wireframes and have any game load up the hacked DLL instead. Not only has ASUS's "cheat" been around for years, but I also contend that someone can write one for the PC that will work with any graphics card.
Now onto cheating. Some of the ways we cheated (would be considered cheating under most people's definitions):
1) changing the invisible-person model to visible
2) changing the person model to emit a really huge glow (so can be seen from behind walls)
3) editing holes into walls
4) using cheat modes that no one else knew about
5) hacking the quake executable so that the server could not send commands to the client (e.g. renaming color to dolor so in capture-the-flag, you could be colored blue but be on the red team)
6) using bots (I hacked up the StoogeBot to remove the SBot name and to disable the "No Bots" kick off -- it was actually a nontrivial hack)
Believe it or not, when we competed in clan matches, we did not use any of the above. We reserved the above as an added toy for when we were in the mood for something different (and it was very much a game of who could figure out how to cheat the most).
There were also other things we did that could be considered cheating because they likewise gave us unfair advantages (but I am guessing that most of you will not consider them cheating):
1) Talking to each other over the phone on headsets
2) Having a tool sit next to the quake player to time quad, RL, and shout out "5 sec till quad," etc.
3) Remembering spawning-point orders
4) Using our 3l33t mice to shoot rockets down for splash damage instead of being a dumb keyboarder and going for the direct hit
5) When running into a room, shooting rockets blindly into known camping spots.
When we played other clans, we did not cheat, and we did not get accused of cheating. When we played against random people online, we would constantly be accused of cheating. "You always have quad! Stop camping quad!" "Actually I showed up at quad 5 sec ago to kill the camper waiting there.""Bullshit! You must be cheating!"
I got so sick and tired of being called a cheater while playing legitimately that I did an experiment:
I played using the bot and the name "Yo Mama." Almost immediately I got called a cheater. Another time, I played using the bot but the name "Thresh" (the best Quake player then). Funny, I never got called a cheater.
The moral of the story is that people get annoyed when they play against a suspected cheater (because only someone with better skillz should be able to beat them -- wouldn't want to shatter that ego) and when a good player playing legitimately is suspected of cheating (because that player wants everyone to know that his skillz are better than theirs -- wouldn't want to shatter that ego). No matter what game designers try to do, people will always find a way to cheat. It will not always be easy to pick out cheaters from non-cheaters. So take all your playing with a grain of salt and don't let it get to your ego. Gaming should be a fun stress reliever, not a stress giver.
Peer review can be plenty effective and nearly[0] immune to bias when the reviews are double-blind: the reviewers do not know the authors, and the authors do not know the reviewers. SIGGRAPH, the premiere graphics conference (and perhaps even more prestigious than the best graphics journals around[1]), uses a double-blind system.
[0] Sometimes the reviewer can figure out the author based on paper content and writing style. Other times, humorous things happen, such as the reviewer criticizing a paper written by author X for not citing previous work by author X.
[1] Unfortunately some old and wrinkled Board of Regents folk who grant tenure still think journals are better.