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Simulating Cloth in CG
monty writes: "Creating realistic clothing in games may not seem that difficult, but according to one of Intel's research programmers it turns out it is very difficult indeed. Intel senior technical marketing manager Dean Macri gave a presentation at the recent AGDC outlining the problems with simulating cloth, and some possible solutions. There is an online presentation (including downloadable source code and a fully configurable executable of the demonstration simulation) at The math is a bit intense, but the implications are that realistic cloth simulation remains out of reach for today's processors."
Monty found it on BigKid, but I couldn't ;)
You can improve the rendering of the hair on your newscaster by picking any color other than bright green. Optimize the little things first before you try more sophisticated hair rendering algorithms.
If tits were wings it'd be flying around.
Ahh, yes. I remember them, as well.
The company that produced Clothreyes also did Cartoonreyes, Metareyes, etc. I believe their name is Infographica. You can find out more here
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Rob Flynn
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Rob Flynn
Pidgin
You see, this is just another excuse for the makers of Tomb Raider to keep Laura Croft in skimpy outfits...
"Well, we'd like to cloth her more, but it's just so hard to simulate!"
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Feminism is the wild notion that women are human beings.
It may just be me, but like I said in the title, "Is this really an issue?" I look more for interesting game play, a good story, and decent graphics. Do I care that the clothing looks realistic? Not really. Do I care that the game obeys the laws of physics? To some extent, yes. But since I play a lot of fantasy and pseudo-fantasy games, those laws get broken a bit. Am I more interested in a good story within the game, motivation for why the characters are doing whatever they are doing in the game, and a good game engine.
I don't want reality in my games. That is what I am escaping from.
Eric Gearman
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Atomic batteries to power! Turbines to speed!
Creating realistic clothing in games may not seem that difficult...The math is a bit intense, but the implications are that realistic cloth simulation remains out of reach for today's processors
Actually I would have assumed it would be very, very difficult to realistically model clothing. I'd have assumed it would be very, very difficult to UNrealistically model clothing. I'm no CG designer (or physicist), but wouldn't it be similiar to realistically model fluid dynamics, only with a whole lot of weird variables thrown in?
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Some packages, such as Lightwave and Maya, have real physics engines for animation. Realistic cloth simulation is not all that difficult... unless you have to do it real time. Maybe the NVIDIA GeForce 12 mega-hyper-championship-edition with it's Strategic Motivation Engine(TM) or the newly advertized PlayStation IX will have the power we all need to see realistic clothing on in Quake MXCCLIV, and this technology can also be applied to organic material simulation, so that the body parts flying, as one get gibbed, can be perfectly accurate and anatomically correct.
"Evil beware: I'm armed to the teeth and packing a hampster!"
Lex orandi, lex credendi.
At a conference a few weeks ago (Learning to Behave - TWLT17 in Twente), there was a speaker from University College Londen who talked about "Efficient Cloth Model for Dressing Animated Virtual People".
I couldn't find the whole article online, but a very rough overview is here.
So far noone has really managed to simulate anything within a fraction of 'realism'. The number of variables that need to be taken into consideration is absolutely horrendous. The nearest we can get without throwing Cray computing power about is a vague approximation.
But...
Isn't a vague approximation enough? Take a recent computer game as an example, say Tekken Tag Tournament or Soul Caliber on the PS2 and Dreamcast respectively. Both these games look damn good. No doubt about that. They're by no means 'realistic', far from it in fact, but who cares? The games are fun. When did gaming take to being real? Its an escape isn't it? Maybe in the future games will look like the world around us, on that day I think I'll be going back to my SNES.
http://twitter.com/onion2k
Allow me to play the cynic for a moment...
So, Intel has studied the problem and determined the answer is "We need faster processors". Is anyone surprised?
If you wish to have stretch and shear, then you don't need 8 virtual springs. 6 will suffice.
a---b
/ \ / \
f---x---c
\ / \ /
e---d
Bend can be added using another 3 springs, a-d, b-e, c-f. 9 springs rather than 12.
Remember that the trianglular lattice is used for most things anyway (see the wire frame pictures on the second page for an example).
Et voila, 25% faster!
FP
Also FatPhil on SoylentNews, id 863
When working at the chemistry department of the University of Arizona, I ended up co-sysadminning a supercomputer called the Ardent Titan. Ardent seems to have disappeared.
The Titan's focus was graphics and vector-processing. A scalar processor loads one register with one value resulting from one operation. A vector processor loads n registers with n values resulting from one operation; think "ADD AX TO EACH REGISTER IN VX[]". Four CPUs in our model, but it supported far more.
One of the sample programs was a flag hanging on a flagpole. It was a 512x512 node swatch of cloth, and it was being animated at 30fps, if I recall. You could drag your mouse to adjust a wind source. As you moved the source, the flag would flap realistically.
I had my one-processor SGI (MIPS 4000 at 100MHz) handle the same basic simulation with 64x64 nodes, a few years later. Of course, the complexity of the simulation increases geometrically with the size of the swatch of free fabric, but it's not THAT terrible.
In essence, the simulator is just an MxN array of nodes, with springs between each node horizontally, vertically and diagonally. The two diagonals can be given opposing compression limits, to emulate the thread bias of cloth. Apply forces to all nodes, and minimize the energy on each node. Take another pass to apply forces of self-collision, where one part of the fabric tries to intersect another part.
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The problem with clothing is that different fabrics "hang" differently. Apparently, this is a big issue in the clothing industry and determines why clothing designers choose different fabrics for different outfits: it isn't just how the fabric looks, but how it behaves. The computer has to emulate the performance of the cloth not just in terms of how it behaves at vertices and how it stretches, but also how it behaves along with gravity. If you look in "Geri's Game", notice how the clothing folds. The designers had to emulate not just the person's body, but the structure of clothing on top of that body (until now, clothing has always been animated along with the body). Don't even get me started on the problems of textures.
In essence, the problem is very, very difficult. It is not so much a question of computing power; we are still working on how exactly to model it in the first place.
... but not necessarily in the sense you're thinking of. Allow me to explain by way of example:
When I saw the new Final Fantasy trailer, I was completely blown away. But it wasn't until I had watched the trailer a couple of times and explored the rest of the web site that I realized that one of the reasons was because the characters seemed to move so very realistically -- especially their clothes.
"Is this really an issue?" Yes, but in one of those subtle ways that is often hard to justify to the bean-counters. To me, the best special effects are the ones that don't call attention to themselves, but rather let the storyline continue. And that goes for movies and games. Since we are beginning to see more and more CG characters on the silver and game screens, any little bit towards realism is a step in the right direction.
In the attempt to escape from reality, are you really satisfied with blocky characters that jerk across the screen? Realistic cloth simulation in no way limits the possibility for "unrealistic" plot, action, character movements, etc. It only makes the characters themselves seem more realistic. If you really want to escape from "realistic" characters, go play on an old NES, or better yet an Atari. Their games have as much action, plot, and challenges as today's games -- but they don't look so realistic.
"I came here to kick ass and chew bubblegum. I'm all out of bubblegum." MSE USC APX AIA CSI CASp