Hello,
I'm learning a lot about skinning & rigging from Gabriele Pellegrini's deep dive into the Unreal Metahuman rig in Maya.
UE Metahuman rig deep dive [youtu.be]

The Metahuman skin deformations are using RBF'S aka Radial Basis Functions. I understand RBF based deformations have been around for many years so I was wondering if the biharmonic capture / tetrahedralization skinning tech is more current & superior ?
biharmonic capture [www.sidefx.com]

With the addition of the new muscle tools in 19 and xsense motion capture integration, I was hoping I could shift the entire Animation & skinning pipeline to Houdini.

Unreal and Unity now have Machine learning deformers so the timing to make the shift might be just right.
UE5 ML deformer [docs.unrealengine.com]

Is there a RBF based node inside of houdini and and an example (free or paid) to learn from ?
I'm looking to use a similar toolset as demonstrated by Pellegrini within houdini so I can skin custom characters using the metahuman rig / RBF solver and send them to Unreal.

Thank you so much for reading so far and hope someone could guide me.
b

behram_patel
The Metahuman skin deformations are using RBF'S aka Radial Basis Functions. I understand RBF based deformations have been around for many years so I was wondering if the biharmonic capture / tetrahedralization skinning tech is more current & superior ?

RBF and Biharmonic Capture are apples and oranges
- Biharmonic capture is an advanced algorithm to compute hi quality linear skinning weights, it's not contributing to deformation solve in a any way, it produces weights and that's it

- RBF solver is a generic term but in this context it can for example be a deformation solver (usually run in addition to simple skinning deformer) that uses RBF interpolation function to interpolate corrective blendshapes (or helper joint poses) based on n-dimensional space of certain joint poses from pose examples
Houdini has Pose space Deform sOP that uses RBF for that purpose for example, it may be a little outdated and workflow wise based on Object level workflow and not ideal for KineFX rigs, but you are free to try
(there is also BlendPose CHOP that is a generic node for doing RBF interpolation from examples)

Rok Andic has been covering his implementation of RBF for pose space deformations in KineFX. The link below is a quick demonstration. If you subscribe to his patreon stream he has some more in depth explanations.

I'll also note that in my experience, most corrective deformations can be done with more simple controls. The most common deformations around knees and shoulders, for instance, often only need a dot product of two bones to drive the deformation. But for areas with multiple blend shape possibilities (especially in areas around the face of characters) RBF allows you to set multiple different "targets" that drive different blendshapes or combination of blendshapes.

https://www.rokandic.com/blog/tag/kinefx [www.rokandic.com]

tamte

behram_patel
The Metahuman skin deformations are using RBF'S aka Radial Basis Functions. I understand RBF based deformations have been around for many years so I was wondering if the biharmonic capture / tetrahedralization skinning tech is more current & superior ?

RBF and Biharmonic Capture are apples and oranges
- Biharmonic capture is an advanced algorithm to compute hi quality linear skinning weights, it's not contributing to deformation solve in a any way, it produces weights and that's it

Houdini has Pose space Deform sOP that uses RBF for that purpose for example, it may be a little outdated and workflow wise based on Object level workflow and not ideal for KineFX rigs, but you are free to try

Thank you for underscoring the distinction tamte. Outside of the FEM based muscle toolset, what would you say is the current / ideal tool in houdini to get good looking skin deformations (Metahuman quality) for games.
As demonstrated here by Riham Toulan : rigging the Metahumans in Unreal Engine [youtu.be]

Thank you,
b

made-by-geoff
Rok Andic has been covering his implementation of RBF for pose space deformations in KineFX. The link below is a quick demonstration. If you subscribe to his patreon stream he has some more in depth explanations.

I'll also note that in my experience, most corrective deformations can be done with more simple controls. The most common deformations around knees and shoulders, for instance, often only need a dot product of two bones to drive the deformation. But for areas with multiple blend shape possibilities (especially in areas around the face of characters) RBF allows you to set multiple different "targets" that drive different blendshapes or combination of blendshapes.

https://www.rokandic.com/blog/tag/kinefx [www.rokandic.com]

Thank you so much for presenting information I can follow through with Geoff. I will sub Rockandics patreon.
There was a very good resource on using the the Dot - Product by marco d'ambros : Rig Plane intersection [vimeo.com] which I found originally on Mateusz Matejczyk (Ziva) website [www.matejczyktd.com]

I got the impression that the RBF approach was more sophisticated and better suited to interop between Maya & UE5.
However long into my past I was a 3Dmax generalist. After using Houdini this last year , going to Maya is very,very panful.
However Meta Human editing pipeline extends to Maya only atm.

I was hoping to create a pipeline that had UE & Houdini interop since Epic isn't going to make that happen any time soon. Hence the necessity to adhere to RBF to stay compatible.

Thanks once again.

b