[x3d-public] HAnim and glTF skins

[Andreas Plesch]

My interest was in supporting animation in glTF inlines  in x3dom. With
basic animation pretty much solved as TimeSensor/Interpolator/Route combos,
the next step is skinned animation. Since HAnim is actually not strictly
limited to humanoids (if the H is ignored), it appears more and more
feasible to use it to represent glTF skins and skeletons in a fairly
complete manner. At least this is what my first manual translations
suggest. I am not familiar with other skinned animation systems but most
can export glTF.

Another feature in glTF are morph targets which are independent of skins.
They are similar to HAnim displacers but I have not looked very closely if
it is possible to define a mapping between them.

One difference is that morph targets can be used outside of a joint
hierarchy (skeleton) in glTF whereas displacers are confined to joints and
segments within a x3d skeleton. Until displacers are released into the
wild, it would mean that glTF meshes with morph targets have to be wrapped
in a humanoid node. This seems possible.

Implementing HAnim vertex wise deformation ultimately needs to be in vertex
shaders. This may actually mean using a glTF skin representation since it
is perhaps more shader friendly.

-Andreas

---on the phone---

>
> Date: Wed, 28 Nov 2018 16:35:17 -0800
> From: Leonard Daly <Leonard.Daly at realism.com>
> To: x3d-public at web3d.org
> Subject: Re: [x3d-public] HAnim and glTF skins
> Message-ID: <20125083-023f-b96a-6586-ab8e6d3ea128 at realism.com>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> Andreas,
>
> I have read all of the messages with this subject. I am responding to
> the first one because I think that is best where my question arises.
>
> Are you working on an understanding and implementation of H-Anim skinned
> animation in X3D or the more general animation of skinned surfaces that
> is done in Maya/Blender/+ in most every other application/use?
>
> If you are doing the more general case would it make more sense to get a
> good understanding of the process and work-flow that is used in those
> applications and practices?
>
> If the intent is to use H-Anim with X3D, you will need to resolve the
> differences between X3D V3.3/H-Anim V1.0 and X3D V4 (not yet in
> existence)/H-Anim V2.0 (perhaps); as you have noted in one of the other
> messages in this chain.
>
>
> Leonard Daly
>
>
> > I am collecting information on these skinning systems here:
> >
> > https://github.com/andreasplesch/x3dom/wiki/HAnim-and-glTF-skins
> >
> > [This is a editable wiki if anybody wants to add to it]
> >
> > It looks like the less well known
> >
> > jointBindingPositions/Rotations/Scales and skinBindingCoords/Normals
> >
> > fields used for non-humanoid skeletons may be useful but I am not
> > certain how to interprete those fields. Castle may not implement those
> > as a search did not find a match ?
> >
> > My understanding is that the transformation matrix defined by these
> > fields needs to applied before joint trafos are applied. But to which
> > vertices ? The ones listed in skinBindingCoords for sure (if they are
> > indexed by skinIndex field in the joint) but how does
> > skinBindingCoords and skinCoords field interact ? Does the
> > skinBindingCoords field take precedence ? But why then have both
> > fields in the first place ?
> >
> > Could the jointBinding fields equivalently be replaced by a sub-Joint
> > node under the joint the fields map to ?
> >
> > Is there an example using these fields ?
> >
> > Thanks,
> >
> > -Andreas
> >
> >
> >
> >
>
> --
> *Leonard Daly*
> 3D Systems & Cloud Consultant
> LA ACM SIGGRAPH Past Chair
> President, Daly Realism - /Creating the Future/
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> ------------------------------
>
>
> From: Leonard Daly
> Sent: Wednesday, November 28, 2018 4:35 PM
> To: x3d-public at web3d.org
> Subject: Re: [x3d-public] HAnim and glTF skins
>
> Andreas,
>
> I have read all of the messages with this subject. I am responding to the
> first one because I think that is best where my question arises.
>
> Are you working on an understanding and implementation of H-Anim skinned
> animation in X3D or the more general animation of skinned surfaces that is
> done in Maya/Blender/+ in most every other application/use?
>
> If you are doing the more general case would it make more sense to get a
> good understanding of the process and work-flow that is used in those
> applications and practices?
>
> If the intent is to use H-Anim with X3D, you will need to resolve the
> differences between X3D V3.3/H-Anim V1.0 and X3D V4 (not yet in
> existence)/H-Anim V2.0 (perhaps); as you have noted in one of the other
> messages in this chain.
>
>
> Leonard Daly
>
> I am collecting information on these skinning systems here:
>
> https://github.com/andreasplesch/x3dom/wiki/HAnim-and-glTF-skins
>
> [This is a editable wiki if anybody wants to add to it]
>
> It looks like the less well known
>
> jointBindingPositions/Rotations/Scales and skinBindingCoords/Normals
>
> fields used for non-humanoid skeletons may be useful but I am not
> certain how to interprete those fields. Castle may not implement those
> as a search did not find a match ?
>
> My understanding is that the transformation matrix defined by these
> fields needs to applied before joint trafos are applied. But to which
> vertices ? The ones listed in skinBindingCoords for sure (if they are
> indexed by skinIndex field in the joint) but how does
> skinBindingCoords and skinCoords field interact ? Does the
> skinBindingCoords field take precedence ? But why then have both
> fields in the first place ?
>
> Could the jointBinding fields equivalently be replaced by a sub-Joint
> node under the joint the fields map to ?
>
> Is there an example using these fields ?
>
> Thanks,
>
> -Andreas
>
>
>
>
>
> --
> Leonard Daly
> 3D Systems & Cloud Consultant
> LA ACM SIGGRAPH Past Chair
> President, Daly Realism - Creating the Future
>
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