Believable characters are essential part of modern games. Clothing (hair, ornaments, etc) with dynamic and realistic behaviour gives a great opportunity to make game character more authentic, however traditional animation is not flexible enough to handle fully physically realistic clothing, not to mention that animating every detail of complex cloth motion is nearly impossible. Solution (that is already used some in games) – physical simulation of the cloth itself.

Answering industry demands, specialised cloth and clothing simulation middleware are emerging on the market. Let’s take a look on promising of them:

1. APEX Clothing from NVIDIA

You might be already familiar with APEX Clothing – clothing simulation module, part of NVIDIA APEX Framework. APEX C is using constrained cloth approach (Hybrid Clothing, as NVIDIA calls it) – since regular simulated cloth behaves too unpredictably, physics mesh is constrained to the animated mesh (degree of freedom is controlled by artist).

APEX Clothing consists of two components – run-time and authoring. Run-time component is responsible for providing data for rendering, cloth simulation (by making necessary calls to PhysX SDK) in actual game environment, asset deserelization and LOD system.

Authoring component is used to specify cloth behaviour, parameters and free motion restrictions via DCC PhysX plug-ins for 3ds Max and Maya, and standalone Clothing Tool application.

APEX Clothing is available for Xbox 360, PS3 (with appropriate optimizations) and PC. However, PC version not only supports CUDA GPU acceleration, but also can take unusuall advantage from multi-core CPU configurations, as clothing simulation runs in compartments (sub-instance of one type of physics simulation) by default.

So far, Clothing module was used in several games (Mafia II and EvE Online: Incursion), and we can assume that it may become popular in the future, since APEX was promised to be available for free (only one from all the solutions listed in this article) for all developers, and is already integrated into several major game engines, like UE3/UDK.

2. Havok Cloth from Havok

Havok Cloth was one of the first additions to now greathly expanded Havok Products family, revealed for the first time at GDC 2008. Various Havok solutions are widely used in games on consoles and PC, and Havok Cloth was introduced to add cloth simulation capabilities (both character clothing and environmental cloth) to original Havok Physics suite.

Cloth can be authored via Havok Cloth Tools plug-ins for popular moddeling packages, while runtime is fully integrated with Havok Physics and Havok Animation solutions, and is optimized for PC, Mac, Xbox 360, PS3 and Wii platforms.

Havok Cloth is available for licensing and can be already seen in several released games, like DJ Hero, Heavy Rain and Sports Champions.

3. Shroud from Cloak Works

Shroud Engine – cloth and softbody simulation solution, presented by a newcomer (but “composed of game industry veterans“) Cloak Works company. Recent interview with Joe van den Heuvel, Cloak Works CEO, can give a better introduction on Shroud concept and capabilitites then we can possible provide.

Standalone tool – Shroud Studio can be used to author clothing parameters (game models and animations can be imported in FBX or Collada formats) and preview its behaviour (Shroud Studio is using Ogre3D for rendering).

Runtime component of Shroud engine allows easy integration with existing subsytems of game engine, like rigid-body physics or animation.

Shroud is positioned as ultra high-performance solution, capable of showing up to 10x performance improvement over competition. Comparison table is provided below.

However, results must be taken with a little grain of salt – authors are comparing “latest build” of Shroud engine with rather old versions of competitor solutions. We are not sure about Bullet, but in PhysX SDK 2.8.4 (used in APEX Clothing) cloth solver was updated and simulation performance has improved significantly, so it would be interesting to see actual performance data.

Currently, Shroud is in beta and there is no information on games in development that will rely on Shroud engine. Licensing options and availability of console versions are also unknown.

4. Carbon from Numerion Software

Numerion Software, company founded in November 2009 by a small team of former Criterion Software developers, has announced Carbon framework – unified physics engine supporting the simulation of soft- and rigid bodies and motion constraints.

Carbon has evolved from a physics technology used internally by Electronic Arts in games such as Fight Night, FIFA, SKATE, NFS, etc on PC, Xbox 360m PS3 and Wii – great service record to start with.

Carbon engine provides interesting capabilities on high-performance softbody simulation, that can be used to model 2D soft bodies, such as cloth, or 3D volume preserving soft bodies such as flesh

Closed beta of Carbon will be available in April, and current plaforms only include Windows PC, Linux and Mac OSX.

To summarize:

APEX Clothing – affordable, Havok Cloth – reliable, Shroud – fast, Carbon – advanced.

What will take place in future games ? Only time will show.

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