poseDeformer and blendShape hack

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  02 February 2013
poseDeformer and blendShape hack

Hi guys,
I was just playing with Comet's posedeformer and tried to change a little the maya's blendshape connections to simulate a posedeformer. It seems to work a little and I'd like to know what do you think and if I shoudl go on on this direction or go back to Comet's. However it seems really a too simple solution so I guess it's gonna break somehow...
I attached "pippoBlending".ma as an examble(where I just animated the blendshape wight and it becomes active at frame 10).

Here we go; let "pippo" be a mesh, with a skeleton and a skinCluster deformer associated; let "pippoShape" be the output mesh of the skinCluster deformation.

1) create 2 "virgin" meshes (createNode mesh, a priori no shader), pippo_cloneShape, pippo_correctShape

At the end, pippoShape will be hidden, pippo_cloneShape will be the output mesh and the third one the blendshape correction.

2) feed the skinCluster output to the 2 virgin meshes (i.e. connect pippoShape.outMesh to pippo_cloneShape.inMesh and to pippo_correctShape.inMesh);

By doing so, the deformation of pippoShape drives the original shapes of its copy and the potential correction (working this way is it equal of working in "pose space"?)

3) perform a blendshape between pippo_clone and pippo_correct as master (as it was a standard blendShape);

4) move the original pippo in a troubling pose and sculpt pippo_correct;

5) "connect/blend/drivenkey" the blendweight to the troubling pose (as you wish);

The idea is that the tweaking (in world space) you do in the correction are dragged by the base mesh of its node, which deforms along the original skin deformation... probably this is equivalent to a scuplture in pose space??? I don't know. If I'm not wrong, this should be pretty alike an easy posedeformer since it seems to allow the sculpting of the blendshapes in pose space. For easy correction, it seems to work, but I'm puzzled if in more complex situations it could.

You guys think it's a suitable solution or should I go back to Comet's posedeformer or to the classic blendshape inverse correction script?

At the end, one just would need a little scipt to perform the connection of the meshes, nothing more I think and it works as the usual blendshape with multiple masters...

Attached Files
File Type: zip pippoBlending.zip (6.6 KB, 1 views)
  02 February 2013
the key to pose space deformation is that a mesh is affected by deformation first, then is posed in maya's terms, blendshape deformation comes first, skin cluster after that.

any deformation chain where skin cluster is first will mean that your blendshape points still move in worldspace, not pose space.
ngskintools.com - skinning plugin for Autodesk Maya
  02 February 2013
you're right, at the end is not in pose space, but by making the blendshape target dynamic, for corrections as in the elbow/shoulders it's not very far from that (it seems to me)
  02 February 2013
haven't checked how scene looks like, but it sounds to me this would be a good test - after setting up the corrective, try posing your character in a different pose (say, turn whole character 180deg first, then put arms in non-default pose) and then test that elbow. usually if that looks good both in endpoints and in transition, you're good to go though I'd imagine you'll get some weird results, like character getting back to sculpt pose or verts moving not where they would have to.
ngskintools.com - skinning plugin for Autodesk Maya
  02 February 2013
hi, you're 100% right
As soon as I move the other joints, it breaks; with a single joint it's not so evident, but with more than two joints "actives" it's indeed pretty far from being in local space and it doesn't work... so back to the standard solution of inverting the target!

thanx man
  02 February 2013
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