Quite some time ago I stumbled across a pretty neat plugin for maya that is designed to help with modeling corrective blendshapes. I don’t remember where I found it but it came with an Xcode project and I think the credits go to James Jacobs, whos name is listed inside the code. So, thanks James, wherever you may be, this is just some awesome tool!
As it is with these plugins, they usually only run with the maya version they were compiled for and so it was just great to have the Xcode project to be able to compile new versions as new maya releases came along.
So, finally I just compiled a new version for the current maya version and wrapped it in a zip file along with two scripts plus icons that help with the easy task of extracting corrective shapes. I have been working with this for some time now and it really helped to reduce a lot of painstaking modeling time.
I finally converted the original plugin to python in order to make it available to Maya users on all platforms.
Along with a couple of modifications I also changed the actual command, so if you have used the extractDeltas plugin before you might want to update your shelf buttons or hotkeys or whatever is linked to the plugin.
Also, the scripts which were previously coming with the plugin are now included in the code so that you only need to load the plugin and the commands will be available like before.
The command for extracting the model is pretty straight forward:
extractDeltas -s <mesh with skinning but no shape> -c <corrective shape's name>;
The scripts which are included in the plugin supply you with two commands to help with the process. extractDeltasDuplicateMesh creates a simple copy of the selected skin object (polygons only), deletes the intermediate object and unlocks the transform attributes.
performExtractDeltas makes sure that the correct objects are selected and runs the command with the selection. The script expects you to have the bound geometry selected first and then the modeled corrective shape.
Please note that in order to make the plugin work correctly you need a skinned mesh with a clean history. This means that it’s best if you only have your blend shape node followed by the skin cluster. If you have any additional nodes in the history or even deformers after the blend shape node the extraction process will most likely fail. If you are looking for a more advanced correctives workflow take a look at SHAPES.
The following short video demonstrates the use of the scripts and the plugin.
Happy modeling ;)
Download: extractDeltas.zip (OSX, Windows x64 and Linux x64)