Dual Quaternion skinning in Maya

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Dual Quaternion skinning in Maya

 

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This Maya plugin implements a smooth skinning node doing dual quaternion skinning. It is described in the tech report "Dual Quaternions for Rigid Transformation Blending" by Kavan et al. (see also his page ) Basically, it does the same as a skinCluster node. The plugin adds a new Maya node called "skinClusterDq". As it is quite involved to set up a skinning network in Maya (which is hidden from the user by some MEL scripting), setting up a skinClusterDq node is done by copying the internal Maya structure for an existing skinCluster node. MEL helper functions are provided to do this.

 

License

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This software is provided 'as-is', without any express or implied warranty. In no event will the author(s) be held liable for any damages arising from the use of this software. Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions: 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required. 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software. 3. This notice may not be removed or altered from any source distribution. Contact ======= This plugin was written by Guido de Haan. Many thanks to my employer, Guerrilla (), for letting me release this project publicly as it was partially written in company time.

 

Quick start

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1) Make sure you load skinClusterDq.mll 2) Make sure you load the skinClusterDqUtils.mel script 3) Create or load a scene with skinClusters in it 4) Call the MEL function 'createSceneSkinClusterDq' to create skinClusterDq nodes for each skinCluster node in the scene. NB: This can take some time as all attribute values/connections are copied one-by-one. 5) That's it...

 

skinClusterDq node

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 You can see the difference between dual quaternion skinning and normal Linear Blend Skinning (LBS, as done by Maya's standard skinCluster node) by changing the "skinningMode" attribute of the skinClusterDq node. Easiest way to change this is to select the skinClusterDq node and open up the attribute editor. There are 3 possibilites for setting the skinning mode: 0: LBS - Linear Blend Skinning Default skinCluster behavior 1: DQLB - DualQuaternion Linear Blending Skinning with fast dualquaternion blending 2: DQIB - DualQuaternion Iterative Blending Skinning with iterative dualquaternion blending. Higher quality, but more expensive. When you created the skinClusterDq node via 'createSceneSkinClusterDq' or 'createSkinClusterDq', the skinClusterDq is linked to the original skinCluster node via a message attribute called 'origSkinCluster'. Other MEL utility functions use this to e.g. switch or copy settings from the original skinCluster node.

 

Weight Painting

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When you replaced a skinCluster node by a skinClusterDq node, starting the weight painting tool refuses to work. This is due to the MEL scripts handling the weight painting are expecting a skinCluster node to be present. It uses the 'skinCluster' command to query all sorts of information, most importantly the influence objects. To make it work with the 'skinClusterDq' node, some minor modifications were needed of the original Maya MEL scripts. A modified version of 'artAttrSkinJointMenu.mel' (Maya 7.0) is included and contains some small changes that were necessary to make it work again. After you loaded this script, you can start painting weights using 'artAttrSkinDqToolScript 3', as opposed to the normal behavior 'artAttrSkinToolScript 3'. See MEL Scripts section for more info.

 

MEL scripts

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1) skinClusterDqUtils.mel Contains several helper functions to support skinClusterDq workflow. Most important ones are: * createSceneSkinClusterDq: Create 'skinClusterDq' nodes for each existing 'skinCluster' node in the scene * createSkinClusterDq(string $skinClusterNodeName): Create 'skinClusterDq' node for given 'skinCluster' node and reconnects Maya graph from old skinCluster node to the new node. NB: This can take some time as all attribute values/connections are copied one-by-one. * toggleSkinClusterDqOutput(string $skinClusterDqNodeName): Toggles geometry output of a skinClusterDq and its corresponding skinCluster node. You can return to your original skinCluster node with this, in case some standard MEL scripts refuse to work when a skinClusterDq node is attached instead of a skinCluster node. * syncSkinClusterDq(string $skinClusterDqNodeName): Copies all settings from the original skinClusterNode to the given skinClusterDq node. * syncSkinCluster(string $skinClusterDqNodeName): Copies all settings from the the given skinClusterDq node to its original skinClusterNode. * artAttrSkinDqToolScript(int $setToTool): Copy of artAttrSkinToolScript() which starts the skin weight painting tool. Weight painting will not work by default as its MEL scripts assume it's working with skinCluster nodes and not with skinClusterDq nodes. The biggest problem here is that the 'skinCluster' command is used in a lot of places. To start painting, use 'artAttrSkinDqToolScript 3'. 2) AEskinClusterDqTemplate.mel: Provides Attribute Editor settings for the skinClusterDq node. Hides most of its input attributes. Copied from AEskinClusterTemplate.mel 3) artAttrSkinJointMenu.mel: This is a modified version of the Maya 7.0 script $(MAYADIR)/scripts/others/artAttrSkinJointMenu.mel This script handles the weight painting tool window, but uses the 'skinCluster' command to get the influence objects. All calls 'skinCluster -q -inf $NODENAME' were replaced by a call to a helper function called 'artGetSkinInfluenceObjects'. When the $NODENAME refers to a skinCluster node, it will just call 'skinCluster -q -inf'. When it's a skinClusterDq node, it will returns all 'skinClusterDq.matrix' connections as the influence objects. NB: You have to replace this script in order for painting to work!

 

Known Bugs

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Maya's component editor doesn't show skin vertex weights when a skinClusterDq node is used

 

Changes

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2007/01/15: Initial release version 2007/01/18: Fixed bug in "copyInputAttr" and "copyOutputAttr" commands. Destination array attributes were not cleared first, only existing elements were copied. 2007/01/30: Blending quaternions in dual quaternion blending algorithms is now using the quaternion with max weight as a pivot (to make sure the shortest path is taken by sign selection of quaternion dot product). MEL function 'createSceneSkinClusterDq' now returns the list of skinClusterDq nodes it created. 2007/01/31: The clearing of array attributes for "copyInputAttr" and "copyOutputAttr" commands didn't work properly. There's no easy way of doing this using the Maya API, so attempted a different approach. 2007/03/02: Working approach for copying array attributes using the "removeMultiInstance" MEL command to clear the destination attribute before copying. 2007/03/19: Public binary release. Source code will be released on SourceForge.net soon. 2007/03/21: Public release. Visit 2008/03/28: Minor compile fixes for Visual Studio 2005. Added support for (orthogonal) scaling. Added Maya 2008 version.