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Graphics Software

Simulating Cloth in CG 118

Posted by CmdrTaco from the wouldn't-it-be-nice dept.
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 ;)
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Simulating Cloth in CG More

Simulating Cloth in CG

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  • I've seen a preview movie. It certainly was an early look, etc., but it wasn't so great.

    You shoot a gun at a wall and it's completely obscured by smoke/dust/whatever, when the dust clears, there's a jagged, unrealistic hole there. Yay.

    I've always yearned for a "game" with real physics. I want a world to explore. I don't care much for killing things. I'd just like to run around and see things... Mountains, caves, buildings, trees, cool stuff like that. And if I could interact with it, that would be great. And no, I'm not just asking for Myst... :-P

    I was excited when that Jurassic Park game came out with a "complete physics model" where you could supposedly affect everything in your environment. Never played it, heard it sucked. I should have known it was too good (too early) to be true... But someday, of course.

    And someone said they don't want realistic stuff, because they're trying to *escape* reality. Well, yeah, I'm trying to escape reality, but that doesn't mean my escape shouldn't be realistic. I do, however, agree with the sentiment that flash, glitz, glamour, and large guns do not good gameplay make. I want a fun, engaging game.

    ...

    Dammit! :-P
  • Ever played with xspringies? It's great fun playing with masses and springs.

    I'm sure that could be combined into a game. Runs like the wind on my K6-2/300 too.

    --
  • Comment removed based on user account deletion
  • I don't give a rat's ass about games, but I can see all kinds of other applications. I am a fiber artist when I'm not being a geek, and if you think game graphics are lousy, you should see the ones in the sewing or weaving pattern generation software.

    But this is a very large problem, I can't even predict how fabric will behave all the time and I work with it live and in person.

    If this could work, then you could shop for clothes online and see what they look like yourself. There were some attempts at this a while back, but it looked like the child's toy where you mix and match heads and bodies.
  • It may just be me, but like I said in the title, "Is this really an issue?"

    I think it is, but games aren't necessarily the driving issue.

    It used to be that CG in commercials and the like was done for creation of impossible scenes: boxing Listerine bottles, smiling ants, and the like. But more recently, CG has been used in subtle ways to the point that we don't know it's CG. Instead of being used to create the impossible, it's used to create the possible, it's just cheaper.

    Realistic cloth would help with this, and it might also help with online shopping, as you could get a realistic representation of an outfit with different colors, fabrics, and combinations thereof.
  • The biggest problem with their approach is that you can't lightmap stuff that's been destroyed. In fact, if you watch the preview movie, you'll notice this right away. There's a scene where they blow up a tower. Watch as the lightmapping disappears just before it drops.

    Problem isn't that creating dynamic worlds is hard; it's that lightmapping it is killer. Until we get processors capable of real-time dynamic lighting with hundreds of lights, or some other method of mimicking the effect on the fly, games are going to have the same visual flaws that you see here.

    James
  • They used to be plugins , but now Maya Cloth is part of the Maya Unlimited package: Maya Cloth [aliaswavefront.com] Softimage has cloth simulations available as a plugin. Here is one I found: Fabrix for Softimage [reflectionfabrix.com]

  • If I remember correcetly, there was a plugin for 3D Studio Max called Clothreyes. At this time, I can't remember who it was by. It did very good simulation, however.

    For example, I managed to place a sphere on the ground, classifify a small plane as cloth, and the plugin allowed it to properly drape over the sphere.

    Have a nice day, Rob

    ---
    Rob Flynn
  • Well, for clothing. Maya Complete as clothing as an entire section integrated in the program itself, no plugin required. The clothing interacts with the dynamic fields (such as wind, grafity) set in the dynamic mode.

    (you can access the various modes with F2,F3,F4 etc, or just use the pulldown menu at the top-left of the GUI)

    You can have a free evaluation version of Maya here [aliaswavefront.com]

    Furthermore, I saw some threads about the Final Fantasy movie, about how realistic it is. Well, look over the trailer and guess how heavy the characters are. The sense of weight is well, there is no sense of weight.

    This mistake is commonly made in many animations, 2D as 3D. Just take a look at the chariot scene in Dreamwork's Prince of Egypt. It looks like the chariots including horses are less than 20 kilo's each.

  • Yeah.. but the clothing is just not going to be realistic. My choice is just to ask the token gay guy in the office what to wear. haha

    ----------------------------

  • A small tip for ananova.com (Score:3)

    by PD ( 9577 ) <slashdotlinux@pdrap.org> on Monday November 13, 2000 @08:05AM (#627691) Homepage Journal
    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.

  • No, unfortunately it is not even a question of computing time. The problem of clothing animation cannot in general give a correct solution, whatever the amount of CPU time you dedicate to it (within reasonable bounds... Because you can always resort to a purely probabilistic model :-) ). What makes this difficult is collisions of the cloth with itself. Maya's cloth animation has been criticized as much as any other (and BTW, Maya uses the technique by Baraff & Witkin (siggraph98) described the article this story links to).
  • Ahhhh, but the cloth simulations are not realtime. As far as that is concerned we have already seen CG cloth done before. As someone mentioned there is Geri's Game, and even The Phantom Menace, though it used part simulation, part hand animating. There have been also commercials like a Coca Cola spot by Digital Domain.

    Even before that there have been some amazing demos shown at SIGGRAPH. There is the work of Nadia Thalmann at Miralab [unige.ch] and a cloth simulation paper [acm.org]was the cover of the SIGGRAPH 98 Proceedings. It was by David Baraff and Andrew Witkin, both I think are now at Pixar.

    It will still take some time to get realtime cloth simulations, especially for simulating different types of cloths, with good collision detection (self and otherwise) and that it doesn't involve a square pice of cloth like a flag, but something more complex like garnments which are made from shaped pieces. Looking forward to it, but not holding my breath.

  • It looks like the people at yourfit.com [yourfit.com] are tackling this problem for the Real World, so that you can try clothes on, on-line. From their site:

    The Company's core product is the Virtual Dressing Room, serving leading apparel e-tailers. This hosted software allows online consumers to easily create models of themselves and try on clothing in multiple sizes and colors. Consumers receive a visual image of how garments fit and look on their body along with a written description of the fit and a size recommendation.
    The interesting thing is, you'd better create an accurate model of yourself in order for the fit modeling to work well.

    So I can't wait for this to take off, so we can read about everybody cracking the yourfit servers to retrieve the model of that intriguing someone special next door...

  • Computers will be at least tens faster in 2005 and a hundred times faster by 2010. Remember the first photorealistic creature was the water monster in Abyss in 1989; people went goo-goo over 18 minutes of dinosaurs in Jurassic Park, and the past couple years have full feature length GC films. Just wait and see new wonders.
  • Clothing animation is a very challenging problem. Efficient integration is of course an issue, but all methods should give similar solutions, if given enough time to solve the problem accurately.

    A much more severe problem lies in self collisions and response. This has not been addressed at all in the article this story linked to. It has also been largely ignored in the litterature: for instance, in the Baraff & Witkin paper in siggraph 98, they describe their solution for this with a short paragraph which, unfortunately for them, clearly highlights that what they did doesn't work :-). For example, they start with the assumption that the initial position of the cloth (ie at the end of the last frame) is a legal state. This means that if something goes wrong, there's no hope of falling back on your feet. Furthermore, the solution at the last frame simply cannot be considered a legal state, because the body has moved, and something has to be done with penetrations with the body. Even if you move the body at the same time step as the simulation (a wise choice), you still end up with this problem. There are also obvious geometric problems with the approach they describe, but it is best described with both hands or at least illustrations so I won't get into that here.

    To sum this up, the problem of cloth self-collisions is a very complex one. Pascal Volino has proposed a solution to this at this year's CGI (article in PDF here [unige.ch]), but I have only skimmed through it myself, and others in the field have diverging opinions about it. Ironically though, he proposes a solution to this whole cloth self collision problem using the very same technique that Baraff used for the integration (but failed to use for self collisions).

  • It's easy when you're on the other end (the consumer end) of development to say "what's the big deal?" But let me just tell you that it's a HUGE deal. Anything that's going to make it easier to tell a story for an animator is another step forward to making great footage. Simulating cloth is a nightmare; there's nothing available that can do it right yet, and that's why you see most characters with very little hanging cloth today in animations. The point is: don't say, "wow! we can simulate cloth with bump maps, we don't need real - cloth simulation!" because that's just stupid. Any step forward in making things *easy* is a good one. Most of you are on the technical end of things, but still...

    One other thing - this isn't just relevent for games, it's more relevent for computer animation in film. Anyways, games are about speed and performance, not high poly count, real cloth simulation won't be around in games for a while, I can assure you. Your personal computer probebly isn't a render farm :)
  • When did gaming take to being real? Its an escape isn't it?

    So is a vacation. When a vacation can be entirely simulated in a game system, from the overpacking down to the watered down margaritas, that's when our job is complete.

    Todays gaming is all about immersing the player into the environment. Soul Caliber and Tekken Tag look good, but it's still not enough. I want to put a VR helmet on my head and actually feel the punches and smell the surroundings. That would be an escape.

    -Dave
  • I look at Maya's fabric and hair generation, and although it could use for some improvement, it does not seem to be as dire an issue as Dean Macri seems to make it out to be. What I really want to know is how different what Dean is talking about is from what Maya does? It seems to me (and this is just from a dabbling with it) that they both use a particles system with similar, if not exact, systems for the rendering of such objects. I must be missing something, but it seems to me that the fabric modules for current modeling programs (which seems more than adequate) could simply be slid under the hood into a game engine. I agree with Dean in that we do not have the power as of yet to make this practical in our low-power/low-bandwidth society, but I disagree in that his approach does not appear to be as revolutionary as I read it to be. And, IMHO, the math isn't terribly difficult. It's high school Calculus, first semester even. It's probably my ignorance and not his. Afterall, he works at Intel (laughs to self).
    ------------------------------------
    Collin (Rafajafar) C**** (like I would give out my name on /. )
  • CG people don't get cold, so why should they need clothes? Clothing I just a technological anachronism when it comes to CG.

    Now, if all the CG characters were naked you'd have a lot more hair to animate... So perhaps this isn't much of a solution.

    -josh
  • I think, and I could be wrong, that NURBS are meant for static systems of structure in a 3D environment. IOW, they are made, and that's it. The difference in what Dean is saying and what Maya does is that you can create dynamic points in space being the restriction of the object (contradiction alert). Picture fire. It is the dynamic interaction of molecules using a stream of input (oxygen and fuel) and a stream of output (smoke and carbon/ash/whatever). If one were to create fire using NURBS, there would be linkage with little force. It would be static fire, almost plastic in that it can react to force, but the bonds will not break. The only way one could get around it is to create millions of free-floating NURBS and allow them to interact with each other through the medium (heat). This creates some really shiaty fire, IMO, and would not make much sense in the real world.

    The particle system of interaction is different in that it defines a relation between points in space in terms of Physical Forces as opposed to synthetic links. An example of this would be magnetism. NURBs are pure mathematics and do not transfer as well to Physics, so they have no way of describing magnetism. Particle systems, by not relying on connections in space, but forces between points, can simulate the effects of magnetism.

    What Dean is saying in his article is that by using relationships between points in space as opposed to the elasticity of lines between points in space, you can create dynamic fabric interactions. If your hand brushes a NURB (and this is a stretch) the NURB would react as one. If it touches a Particle, that particle would react independent of it's peers, but it's peers would react in relation to it's movement. This is why particles are perfect for fluidic interactions while they are not nearly as practical as NURBS are for solid/quasi-solid models.

    I'm probably wrong about alot in this responce, so be nice if you are an expert.
    ------------------------------------
    Collin (Rafajafar) C**** (like I would give out my name on /. )
  • The difference is Dean is talking about real-time cloth animation. Maybe it is not clear from his article. The Maya stuff looks great but certainly not useful for a game.

    Maya Cloth is based on the Baraff/Witkin solver which Dean talks about in his article. However, the Maya system is made to be flexible and accurate, not fast. It may not work correctly in certain situations (ie: explode) or may take hours to render particularly if their are a lot of collision objects.

    Both of these things are fine in an animation, either restart it or just wait. Neither is acceptable for a game. You need to be fast and robust.

    That is where it gets really hard.

    -Jeff
  • ..but the article is talking about real time cloth simulation, whereas the lobby seen in the Matrix is a chroma shot composited into live action.
  • It may be hard but its getting easier, and these guys are doing a fair job of it.

    http://www.havok.com/

    See the examples, they are not prerendered instead they use a sophisticated physics engine.

    Disclaimer: I dont work for these guys but i know a man who does.

    They even have a dancing baby :)
  • Sorry, but these packages do not produce motion that looks like real cloth in anything other than very restricted situations.... Like draping over simple objects. The technology is a long way from producing convincing simulations automatically.

    Actually, you can achieve amazingly realistic cloth simulation in just about all situations with Maya Cloth, however it usually requires some amount of setup work. Maya Cloth is fully capable of simulating realistic clothing that conforms to the 'skin' of a deformable object (or set of overlapping objects) which forms your character.

    Additionally, there are numerous cloth properties that you can adjust to simulate just about any type of material like denim, silk, cotton, leather, paper, etc and you can apply different dynamic forces such as wind, gravity, magnetic forces, and so on.

    Setup is certainly not "automatic" as it requires letting the clothing 'shrink' onto the body of the character and manually adjusting collision and tesselation factors to achieve realistic cloth simulation and reduce calculation time.

    Once this is done, however, you can pretty much concentrate on animating your character and Maya Cloth does all the rest. A good example of Maya Cloth in action is the clothing on the main character in Stuart Little.

    Paul

  • 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.
    The look good by yesterday's standards, sure. Compare that to today's gaming standards, and they are good, but you know tomorrow will have something better. The standard changes daily, and approximations are only good enough if they meet those standards.
    Most of the story lines, game plots, and genre's have been explored. The latest and greatest fall into technologies hands now, not story tellers. That means more time put into what we haven't virtually maxed out. Making your toys look better than everyone else's.
    When did gaming take to being real? Its an escape isn't it?
    It still is and always will be an escape. Games are an escape, not because they don't look like the real world, but because they don't act like it. They enhanced graphics don't make the game anymore "real" than they were in the 8 bit world. Whether you're fighting dragons, racing down the street running over pedestrians or just designing you're own city, you are still escaping. How many people do those things in real life? And can reset if they don't like the results? The fact that you can see the reflection of a light in a puddle of water, or the shadows of the folds of clothes, just makes the escape itself all the more realistic.
  • Check out www.havok.com they are doing all sorts of realistic simulations.

    (+1 Karma Whore)
    :)
  • Hugo Elias [virgin.net]
    Chris Hecker [d6.com]
    Jeff Lander [gamasutra.com]

    Henry
  • Bump mapping can add texture to surfaces without increasing the polygon count. Take a look at the Lightning demo by NVidia (sorry, Win32 only). One of the options available is to turn on and off bump mapping. With bump mapping on, the NVidia logo looks embossed on the strike plate.

    As for games which implement it, Q3 definitely does; Soldier of Fortune and Elite Force do; I'm not so sure about Unreal Tournament, but the original Unreal (think old-school, like Unreal 206/208 on a 3dfx card) had a feature like that in GLide: whenever you walked right up to a metal crate, it would have an electroplated, galvanized texture. The stone doors in Chizra's temple had an etched look. Perhaps this was done with multi-texturing as opposed to bump mapping (it worked on the Voodoo 2, which I don't think supported bump mapping); either way, it died out as soon as Tim Sweeney screwed around with original Unreal (replacing the weapon sounds with those from the then upcoming UT, screwing around with Steve Polge's bot code, fixing Direct3D, etc.)

    Therefore, why complicate the scene by adding extra polygons for texture when it could all be done via bump mapping? Dented cobblestones on the ground, cracked wood planks, rusting stone; it can all be enhanced by bump mapping.

  • And a computer science minor I am glad to see this it gives me hope that I could find a cool computer science job that has alot of math in it and I do not mean number crunching.
  • Computer simutation of cloth is an old CG problem and very complex one. Simulation systems have been evolving for years (just get out your back issues of Computer Graphics World,) and nobody was even claiming to be near doing real-time simulation.

    There are three forces at work: gravity, centrifugal forces and the tension of the cloth around objects against these forces. This is not trivial.

    Only the force of gravity is predictable.

    The rest are all solutions of simultaneous equations. The more realistic the simulation, the finer the division of the cloth area into matrixes of threads. The number of calculations goes up geometrically.

    We're definitely not there yet.
  • This is fsckin' hillarious!
  • I am married to an artist, and have often seen the struggles she and others have to get a passing fair representation of draped cloth (and that's when they drape it the way they want it.)
  • How about virtual Strip Poker?
  • Currently, Volition is working on a first-person shooter game called Red Faction [redfaction.com]. The Geo-Mod engine features "real-time, arbitrary geometry modification" (you can blow up bridges and sniper towers, and they fall, completely unscripted! You can also fire the rocket launcher into the ground or at walls to create holes) and "Advanced physics simulation - supports falling geometry, particles and liquid" (you can blow holes in the ground next to a stream, and channel liquid into it!). This might be a control nightmare, but it looks promising. PC Gamer had a scoop on the game back in their August issue, but unfortunately, they don't archive on their website (at least for previews). I wouldn't expect to see this game released for another year; I foresee many control problems that may arise by having such a dynamic world created with everything unscripted.
  • I don't want reality in my games. That is what I am escaping from.

    I agree with you to a degree; reality is boring. Imagine a fighting game that, if your character took too much damage during a fight, required you to "play" through 2 months of game time recuperating in a hospital. More realistic, but less fun. Graphical realism, on the other hand, is something that generally doesn't alter the gameplay/fun factor (with exception of excessive polygon counts slowing down the rendering engine). Compare and contrast playing something like Quake 2 with and without a 3D accelerator; even if you "rigged" the fps count to balance things out a bit, there's just no getting around the more aesthetically pleasing visuals from the more "realistic" rendering.

    As long as game designers don't go overboard ("If you do too many kicks, it causes a realistic physical simulation of a tear in your pants, which then drop to your ankles and make you fall flat on your face."), i don't think it'll be a problem.

  • Seriously, advances that make games more realistic always add to the experience. Nothing can substitute for good game design, of course, but take two equally well designed games, and the one with better graphics is going to be more fun. Why bother moving beyond black and white games? Or wire-frame? Because higher detail allows subtlties to be represented that would be impossible using older technologies. Anyone who's ever tried to puzzle out exactly what the arm flailing in FFVII is supposed to be expressing knows what I'm talking about.

  • 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!"

    But so very easy to stimulate.

  • Rendering realistic cloth movement might be tough, but the CG industry has already perfected rendering pure and unadulterated evil in humanoid form. Witness Jar-Jar Binks.
  • Computer geeks don't have any fashion sense and aren't able to properly dress themselves in real life, naturally they can't do it in the virtual world either, i'm not surprised :)

    ----------------------------
  • Huh?

    Bump mapping is a way of representing high frequency geometrical detail on a low frequency approximation. It has a few disadvantages, (depending on how you do it) - try looking at a bump mapped surface side on, and you'll see nothing but flatness.

    This doesn't really have much impact on modelling cloth.

    Incidentally, the effect you mention in Unreal is called detail texturing, which involves modulating the source texture with a high resolution, but smaller texture at proximity.

    Henry
  • More exactly, the two main problems in computer animation are clothing and hair. Although hair is somewhat more difficult, they aren't really big rendering issues.

    If you look carefully at Geri's clothing, you'll notice some odd quirks -- but I guess it's like watching a magician, you're not as impressionnable if you're a magician yourself. :-) Also keep in mind that in a motion picture production context, simulation is not your only resource; you actually have real people working for you :-). Sometimes you'll have small penetrations into the body or whatever, so you'll just pull a few vertices by hand or even load up the frames in photoshop to paint them...

    As far as hair is concerned, Monsters inc (Pixar's next movie with Disney) doesn't show off any impressive animation. You can see stuff that's just as good, even better, in Mighty Joe Young (yes, most of the shots use a CG gorilla, complete with realistic-moving hair and all). The really challenging part about hair animation is the movement of long hair which interacts with itself. Otherwise, you just need to animate a few long chains (say, one per square inch), and interpolate the rest, and it looks fairly good.

  • Sorry, but these packages do not produce motion that looks like real cloth in anything other than very restricted situations....
    Like draping over simple objects.
    The technology is a long way from producing convincing simulations automatically.
  • Cloth can be a great effect, visually (What would the lobby scene in The Matrix have looked like without the flowing trenchcoats?), but at such great expense it's probably not worth the realtime cost. But to pre-animate the effects on the mesh, storing it as conventional mesh deformation may be an acceptable shortcut in many situations.

    It would definitely enable much larger meshes rendered with greater accuracy. Before realtime is practical, there's always precomputation.

  • "The biggest problem with their approach is that you can't lightmap stuff that's been destroyed."

    Good point, and that's exactly why the lightmap concept is being abandoned soon. The next DOOM will do real-time lighting, as opposed to having the mapmaker do the lightmap compile and the player wait while the lightmap gets loaded. Red Faction might be real-time as well, though who knows right now?

    One other thing: Id Software is doing all their work with the GeForce series on Windows 2000. John Carmack mentioned that before on one of the interviews, and in one of his .plan entries. Apparently, the GeForce will hold up fine while doing real-time light calculations (it must be tied into the vis process somehow; that's the only way to avoid an overload of light sources). The GeForce will play the next DOOM perfectly, as it was intended, while the ATI Radeon will be the runner up. Of course, 3dfx cards will make for nice screenshots, but the Voodoo5 series has little else in its favor.

  • see topic
    "One World, One Web, One Program" - Microsoft Promotional Ad
  • I haven't used Clothreyes, but Digimation [digimation.com] make some amazing plugins, that amongst other things, simulate cloth and hair.

    hummer
  • What Robert says is partially true - the models for clothing are not yet perfect (same with hair, actually, same with many CG issues - you can generally tell CG smoke and water, for example). Modeling clothing and hair requires modeling both a "solid structure" (the body) beneath, and the "soft structure" on top (hair, actually, requires many structures to be modeled - lots of hairs - clothing requires several complex dynamical structures to be modeled). To accurately physically model the clothing dynamics, there are A LOT of variables, and a lot of constraints.

    However, computational power IS a concern in terms of getting realistic hair and clothing into games. Pixar uses a VERY large render farm in making their films, and most of the top quality algorithms are optimized not for speed but for, well, quality. The best of what can be done now requires a lot of computational power. Not until a sufficiently realistic algorithm is completed, though, can one start to optimize it for less powerful computers (and, as with any imaging algorithm, sufficient is subjective - beauty is in the eye of the beholder...)

    But, while these technical issues are certainly fascinating, fun to work on, and of great utility to the digital film industry - the question that hasn't been asked about gaming is: is that much realism actually necessary? (With necessary in the industry being defined as: does it make the game more fun, and thus more people will buy it?)

    My experience in the gaming industry, and VR industry, indicates that the quality of the story, and of the action, outweighs the "realism" of the images. If the industry put more money into the creation of more compelling stories, more engaging games (including less repetition - which becomes harder to do if you need to cache hard-to-render scenes to use them over and over to save CPU time and/or money in up-front rendering basically cell-animation style), and better integration of network interaction into the game plot structure... I think the results would be more fruitful than better and better algorithms for hair and clothing.

    I think researching cool rendering algorithms is fun, and should continue, but the gaming industry could also stand to invest some more money into better interaction design and better writers...

  • It's been already done (Score:1)

    by Anonymous Coward
    A Spaniard (Spanish from Spain :-) company does sell a plugin for 3D Studio MAX that simulated very well clothes. It's called ClothReyes, and it belongs tho the same family of the famous MetaReyes organic modeling tool. Their current web page is here [reyes-infografica.com]. And yes, I'm Spaniard too. -- David Rigel

  • ...Or whatever you call the 64 bit processor that Intel keeps promissing, should put us a good bit forward, but they have a long way to go until rendering realtime will be reality in any game console.

    My second rant... Game consoles are a long way from ever generating the quality of cloth that Maya and others are currently doing for movies. These are two seperate forums that have little in common currently...

    My last and final rant... Why cant we have reality in our games, doesn't that make the fantasy that much more adictive?

  • http://www.bigkid.com.au/articles/00_11/cloth.htm

    I'm not surprised monty managed to find it, especially since he's the admin at BigKid ;p

  • Re:Simulation of Cloth has been here ... (Score:3)

    by RobFlynn ( 127703 ) on Monday November 13, 2000 @12:17PM (#627732)

    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 [reyesworks.com]

    ---
    Rob Flynn

  • You think you're joking, but you've actually hit the nail pretty close to the head. The same reason that superheroes wear skintight outfits (their anatomy is easier to draw without clothing draped over it) applies to video games to an even greater extent. The Quake guy isn't exactly skimpily dressed, but all of his clothes are literally painted on. The same applies to Laura Croft. The less clothes, or the tighter those clothes, on a CG character, the more realistic it will appear until you have a reliable and affordable cloth simulator that produces real-time rendered effects.
  • ... that cloth was a pain in the ass to model/animate.

  • Ah... (Score:4)

    by Electric Angst ( 138229 ) on Monday November 13, 2000 @05:33AM (#627735)
    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!"
    --

  • Is this really an issue??? (Score:3)

    by EFGearman ( 245715 ) <EFGearman@@@sc...rr...com> on Monday November 13, 2000 @05:36AM (#627736)
    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
    --
  • Well, now the 3D porn can put its clothes back on, which is way more sexy than seeing a failed attempt at rendering anatomy.

    I'd like to see some good 3d felt.

    ----

  • You are approaching this problem in the wrong manner. What you should do is save valuable processor cycles by forgoing any clothes at all on female characters. Besides, we all know that "jiggle" effects are more efficient than "ripple" effects or others associated with clothes :)

    (do you hear that roaring sound? i think that's hormones...)

  • Heh... (Score:1)

    by pb ( 1020 )
    Didn't I hear something about Square getting patents on a method for doing this quickly for the Final Fantasy movie?

    Well, I probably saw it on slashdot at some point, if I know me...

    Oh man, I can't wait for that movie...
    ---
    pb Reply or e-mail; don't vaguely moderate [ncsu.edu].
  • You can check out the demo on Hitman.dk [hitman.dk].

    It has tons of other cool physics features as well, falling bodies and the like. It's supposed to go gold this week.
  • Yeah - I remember this is an age old problem. But even if it was possibly to do realistic simulations, they'd be too slow for games.
  • ...you should SEE what they can do in simulating cloth! I mean, those simulated corduroy pillow cases are making headlines.

  • not to nitpick (Score:3)

    by nomadic ( 141991 ) <`nomadicworld' `at' `gmail.com'> on Monday November 13, 2000 @05:41AM (#627744) Homepage
    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?
    --

  • Real time problems only... (Score:3)

    by Paladin128 ( 203968 ) <aaron.traas@org> on Monday November 13, 2000 @05:42AM (#627745) Homepage
    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!"

  • the implications are that realistic cloth simulation remains out of reach for today's processors.

    Depends what you mean by realistic. I once pointed out to some X-Box advocates that the Pentium III 600 MHz (I know its 733 MHz this week) might be a trifle underpowered for physics simulations and received a withering look. In this case I happened to have a colleague who has used a considerably slower processor to create an animated dress as a benchmark, it's since been turned into a cute tech demo. Understanding algorithms and appreciating the machine architecture are at least as important as processor cycles.

    Also, even though I think the X-Box CPU is underpowered wrt to its GPU, something tells me there will be some kickass cloth demos on it.

  • Real phyiscs = real macro scale physics. I remember this package for Lightwave that did physics for clothes and it was awful (and cost >$1500...)
  • Back in 1982, the 3D rendering scenes were relatively easy (16-bit untextured, average scene polycount of 600 I'm guessing). All that the computer had to do was compile a 24-fps scene, which probably took hours. In fact, the compilation process did get fudged up at one point: in the cross-fade between Tron looking at Sarc's destroyer and Flynn trying to drive the recognizer. In that cross-fade, the framerate drops by half, then shoots back up once the first scene was completely faded.

    I wish that they'd release the source code to the Tron scenes; they might make great Quake maps, or maybe the movie could be recreated in Q3! That'd be pretty cool.

  • A while ago in 1993-94, or when SPARCs were like 25 Mhz, Softimage in Montreal did some work on a roller coaster animation where clothes just had to look convincing. Dunno if it made it into their software as I never go it for X-mass. Of course we are still not talking games, this is just for doing adverts only. Anyone seen that at a Sigraph?

    Since then Microsoft bought it, and errr... well...

  • Virtual clothing (Score:3)

    by Titanhead ( 24709 ) on Monday November 13, 2000 @06:33AM (#627750) Homepage
    At a conference a few weeks ago (Learning to Behave - TWLT17 in Twente [utwente.nl]), 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 [ucl.ac.uk].
  • Havok [havok.com] have lots of physic simulation demos - including one of cloth. The dancers are pre-programmed but the cloths movement happens in real time.
  • I kinda have to agree with you there. I'm sure most people buy a game based on playability, rather than attention to detail. However, I do always maintain at least one game to show off the power of my system.

    Still, it would be pretty cool to say my level 80 barbarian looks fly in his crushed velvet pimp outfit.

  • I don't want reality in my games. That is what I am escaping from.
    That's right, you don't want reality in a fantasy game, but you do want immersion. The whole strive of (most) video game graphics is to create as much of an immersive appearance as possible. This is to enhance the escapism that you experience.

    Picture super mario bros on the NES, and then picture the exact same gameplay, but it 3d, ultra hi-res VR with force feedback. I know which one is going to be much more convincing to your senses. When you're playing games (to use this as an example) where the supposed 'clothes' on the characters are rigid and taught (a la Lara Croft) it is one out of many little things which disrupt the fantasy experience.

    Games are much more exciting, as the illusion that you are there is greatened. When you can believe the illusion created by the graphics etc, then you'll feel much more adrenalin or distress or whatever emotions you feel playing games, because your senses are being fooled into thinking it's real.

    On the other hand, if the gameplay was affected by the clothes (picture the character in Jedi Knight being caught up in his cloak as he tries to swing the lightsaber around), it would probably be pretty dumb. However, better immersion (through graphics, sound etc.) can only help the experience.
  • >where the supposed 'clothes' on the characters are rigid and taught (a la Lara Croft) it is one out of many little things which disrupt the fantasy experience.

    I don't know about you, but the words rigid and taut in regards to Ms Croft are hardly disruptive to my fantasy experience.

  • But if Hasbro were to release Geek Fashion Designer for Windows and Linux, we would be able to learn how to dress ourselves appropriately. I can't wait.
  • So, Intel has studied the problem and determined the answer is "We need faster processors". Is anyone surprised?

    The purpose of that research group at Intel is to find new ways to use up CPU time. Really. I've been down to visit that group. I do physically-based animation [animats.com] myself, so I'm familar with that crowd.

    Cloth is hard to simulate because cloth has hard tension limits. This makes the numerical problem stiff, and you can't just integrate the springs and dampers explicitly. You have to either use a constraint solver or an implicit integrator, both of which are slow. This class of problem (integration of stiff systems of differential equations) takes more numerical work than it seems it should. Work continues on speeding it up.

  • Imagine you want to look at how something would fit you from a website. Say maybe http://www.jcrew.com/ or http://www.landsend.com/cd/frontdoor/ You might want to put in your body-type and see how the shirt would look on you. As of now companies need to make the clothes in order to see how they will react. This is why there is an entire industry of fit models. (no for the most part they are not hot.) They try on the clothes and then have the designers and production people look at them and say "that underwear needs more lycra, she is looking a little too cheeky." Real world application, yes. Interesting, no.
  • Havok [havok.com] is an Irish company who have written a full newtonian physics engine for win32 and PS2. Their site has loads of information on it (not necessarily technical, but lots of demo movies and actual demos [havok.com]). They even have two demos which showcase cloth in particular.

    I've also checked out some of their competitors (mathengine [mathengine.com], etc) and havok seems miles ahead. Unfortunately, I don't think havok supports any open source platforms.. I can't imagine they're not working on that, though.

    cheers,
    -o

  • Now we can finally manage to do on a computer what the Greeks did 2,500 years ago --- draping cloth over a body to make it appear realistic.
  • I think they have hair patents too, but keep in mind that there is a world of difference between rendering the Final Fantasy Movie and playing Quake 3. "Fast" probably means it takes like 5 minutes to do the calculations instead of 30. Not exactly applicable to real-time games, which is what the article talks about.

  • Allow me to be a cynic also. Did you read the article? It wasn't at all an attempt to plug their CPUs. It was purely academic, and was gratuitous with it's references. It was a just a study in cloth deformation, in fact, there was no mention of intel-centric optimization--- take look at the code. sheesh, from the people that gave us VTune, it looks like they don't even use it!

    I like the fact that Intel spends its vast resources taking on interesting stuff like this, AND OPENLY publishing its work. They actually pay someone to sit around and write 3D code that has virtually no impact on their profitability (at this point, anyway...) for the sake of research.


    ---

  • Pixar has improved their shadow algorithms greatly since "Geri's Game". Based on a new method presented at SIGGRAPH 2000 [siggraph.org], hair can be self-shadowed in a more efficient manner while producing a higher quality result. Categorized under the Image Based Representations [siggraph.org] paper section, Deep Shadow Maps (PDF available) [stanford.edu] will greatly enhance modelled hair, fur or smoke. I've heard that this new algorithm has already been encorporated into Renderman and I believe was even used in Toy Story 2. Who needs clothes when you can cover every character in fur or hair? :^)
  • This was my first reaction too, but when I started playing with his math myself, I discovered that an orthogonal method keeps the math much simpler.

    If you look closely, the triangular lattice is composed entirely of right triangles before deformation.
  • Have you never seen a "high" priest in Spandex? Guess you weren't a choirboy, then.
  • Note well that this technique is in the process of being patented by Pixar. I have no idea how much they are trying to patent, when it may grant, and all of the other pertinent information. I do know that they make no mention of the patent in their Siggraph paper. thad

  • Realistic simulation of anything. (Score:4)

    by onion2k ( 203094 ) on Monday November 13, 2000 @05:43AM (#627772) Homepage
    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.
  • Sometimes research into an issue like this will develope useful algorithms that can be utilized for other things.

    The reason for this is that they're not only 'simulating clothing' but utlizes advanced paralell collision detection, deformation algorithms, numerical integration and so forth.

  • Anyone can do it with enough time and CPU power... the problem is doing it realtime. An 64-CPU SGI wouldn't be able to do it even close to real time.

    "Evil beware: I'm armed to the teeth and packing a hampster!"

  • Big surprise (Score:4)

    by Chris Pimlott ( 16212 ) on Monday November 13, 2000 @05:46AM (#627776)
    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?
  • It would seem difficult to buy a computer these days at less than 600MHz; that's an IMPRESSIVE amount of power. But when I go look at the store, there aren't games that need more than 300MHz. So there aren't games that need a new computer for the majority of gamers (faster frame rates, true, but not a convincing thing for most gamers). So I don't think the CPU power will be out there for this until games start requiring more CPU power incrementally. Also, TnL graphics take a bit of CPU load off, thereby improving things. But basically, I think games need to start demanding more CPU power. It's out there, so use it!
  • 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
  • What you should do is save valuable processor cycles by forgoing any clothes at all on female characters.

    Ah, but games usally have male characters too. Do you want them all to be nekkid or clothed in spandex? I guess one could save processor cycles by putting them all in rigid body armor, but while that may be suitable for warrior characters and the like, it seems a bit odd on galactic emperors and high priests.

    Realistic clothing may be neat eye candy in games - and that's a Good Thing - but it can't make up for poorly designed rules or a boring concept.

  • Saw this stuff in 1988! (Score:4)

    by Speare ( 84249 ) on Monday November 13, 2000 @06:52AM (#627782) Homepage Journal

    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.

  • Pixar short (Score:5)

    by RobertGraham ( 28990 ) on Monday November 13, 2000 @07:01AM (#627783) Homepage
    The two big problems in CGI have been clothing and hair. This is why Pixar created the animated short "Geri's Game [pixar.com]": it showed off some impressive new clothing algorithms, though they still couldn't do the hair right. However, I've seen the preview to Pixar's next movie that includes a hairy monster: the hair is amazing.

    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.

  • Pixar's patent on scalar fields on subdivision surfaces has already been granted. This includes some of the techniques used in their cloth animation system (e.g. the "starch" scalar field applied over Geri's shirt to specify how malleable the cloth is over its surface).

    Pixar has a history of software patents. Probably the most silly one is a patent they got during the 80s, and extended in the early 90s, on certain kinds of Monte Carlo integration. Oh, yes, and Pixar also claim an interface copyright on the RenderMan API and RIB protocol. They do NOT play nice with so-called "intellectual property".

    Pixar would be one of the coolest companies in the world if Steve Jobs weren't in charge. :-)

  • I guess my point here is that most games seem to require a 300MHz CPU, when I can't buy a new computer running at less than twice that speed. Why not 450MHz? I agree, you can't require a new system, but most of the gaming community, not just the high end, has a moderatly new system. The only way the games get the increased CPU power is if they demand it. Yes, I am advocating the increasing CPU power/ software need cycle; it makes cooler games. I just don't want my OS/ word processor/ email client involved. My system is over 2 years old (processor) and isn't even pushing the upper limits on any games out there. So, to all the game developers out there, keep up the good work, and write something to make use of the 1.2 GHz Thunderbird I am going to upgrade to in a few weeks.
  • Computer graphics is an exercise in modelling.

    Practically every technique that is in use in graphics today (specifically, and particularly, in games), is a model, an approximation to the real world. Texture mapping, polygonal approximation, simplistic lighting models - all of these are convenient, efficient, and realistic looking models of real life.

    What the story appears to say is "computers are far away from this particular model". Well, that's always going to be true, since the model can always get more realistic and detailed, up until the limits of understanding particle interaction in modern physics.

    The presentation itself is very interesting, and also presents some models that are somewhat feasible for limited use in today's applications.

    Henry

  • Alias/Wavefront has plugins for Maya that simulate hair/cloth, and has had them for quite some time. I've seen demos with hair/cloth turned on that are quite stunning. Unfortunatly I can't seem to find the link on their webpage Alias/Wavefront [aliaswavefront.com], but they have a demo movies [aliaswavefront.com] section. In particular, watch Bingo and look at the small girl's dress. This is an old demo, but I think they used an early version of the cloth plugin to make it (which is why the dress looks a little plasticy).

  • Yes... (Score:4)

    by flieghund ( 31725 ) on Monday November 13, 2000 @05:55AM (#627797) Homepage

    ... 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.

  • There's so many people with computers and on the net who are interested in Pr0n these days, who's going to care about being able to generate fake clothing on characters? :-)

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