[x3d-public] HAnim skinned deformation

[Andreas Plesch]

Primitive restart would be available for webgl2:

https://www.khronos.org/registry/webgl/specs/latest/2.0/#NO_PRIMITIVE_RESTART_FIXED_INDEX

I was also trying to think to think of a way to offload the matrix
multiplications per vertex to the GPU. Instead of just a single world
transformation for each geometry, it would be necessary to have a
transformation matrix per vertex. Hopefully, the uploading of all the
matrices per frame to the GPU would not negate the computional
performance gains.

-Andreas

> Date: Sun, 15 Jul 2018 21:10:43 -0600
> From: GPU Group <gpugroup at gmail.com>
> To: X3D Graphics public mailing list <x3d-public at web3d.org>
> Subject: Re: [x3d-public] HAnim skinned deformation
>
> There's a thing in GLES3 if x3dom can detect that availability.
> https://www.khronos.org/files/opengles32-quick-reference-card.pdf
> page 3 > vertex arrays > Primitive Restart
> And I haven't tried primitive restart. You know how IndexedFaceSet has an
> index, with -1 to indicate the end of a face?
> Well that -1 can be the restart index. Then I don't know what I was
> thinking but somehow I thought that related to HAnim, in particular the
> ability to write a shader that works on an indexed face set, rather than
> more basic primitives like triangle fan. And so for HAnim you won't need to
> rebuild triangle fans on every frame - just modify the vertices and normals
> in-place, and re-send the same indexes with -1 to end each face or triangle.
> Hope that idea works, haven't tried it. -Doug
>
> On Sun, Jul 15, 2018 at 6:41 PM, Andreas Plesch <andreasplesch at gmail.com>
> wrote:
>
> > Further observations
> > On Fri, Jul 13, 2018 at 4:36 PM Andreas Plesch <andreasplesch at gmail.com>
> > wrote:
> > >
> > > Some partial answers:
> > >
> > > On Thu, Jul 12, 2018 at 8:18 AM Andreas Plesch <andreasplesch at gmail.com>
> > wrote:
> > > >
> > > > Before diving into an HAnim skinned deformation for x3dom, there are a
> > few questions:
> > > >
> > > > proto
> > > >
> > > > Is there a proto implementation for skinned deformation, eg. the skin
> > related fields ?
> > >
> > > Boxman has a script which does some skinned deformation:
> > >
> > > http://www.web3d.org/x3d/content/examples/Basic/
> > HumanoidAnimation/BoxManIndex.html
> > > http://www.web3d.org/x3d/content/examples/Basic/
> > HumanoidAnimation/BoxMan.js
> > >
> > > The scene uses native HAnim tags. It may or may not work in x_ite with
> > > HAnim protos.
> >
> > Joe has a native tag BoxMan with test skin deformations.
> >
> > > The script just applies the weights as factors to a transform matrix
> > > which may be quite different from the blending of coordinates. Of
> > > course, the weights can be generated in the first place in such a way
> > > that this application could work.
> > >
> > > > examples
> > > >
> > > > Are there examples in addition to Joes kicking player ?
> > >
> > > There are the Lucy avatars available from seamless3d:
> > > http://www.seamless3d.com/hanim/
> > > I had view3dscene convert them to xml:
> > > https://github.com/andreasplesch/x3dom/blob/HAnim_work/test/functional/
> > HAnim/Lucy_test4.x3d
> >
> > All players I tested which have skinned deformation implemented show
> > the Lucy animation with inverted rotations. The players are:
> > view3dscene 3.18
> > BSContact
> > freewrl 4.0
> > Probably there is a problem with the Lucy example and perhaps how
> > seamless3d exports hanim.
> >
> > > A maria_noscript model was also available at some point but seems lost.
> > >
> > > > skinCoordWeight
> > > >
> > > > This field modulates the transformation applied to the indexed coords
> > by a factor ranging from 0 to 1. It is not quite clear how the factor
> > should be applied. The spec. focuses on the amount of rotation but scaling
> > and translation presumably should also be affected.
> > > >
> > > > Should scaling and translation be weighted ?
> > > >
> > > > The most straightforward way would be to just scale all the components
> > of the transformation matrix. However, that does not work for the
> > rotational components. Is there a recommended way to apply the weights to
> > the complete transformation matrix ? Multiply all the individually weighted
> > field matrixes ? That would be a lot of matrix multiplications, for each
> > coord for each frame of an animation.
> > > >
> > > > skinNormals
> > > >
> > > > The spec. only refers to the skinCoords as being affected by the
> > weighted transform. Presumably the skinNormals also need to be transformed ?
> > > > If so, it seems to make sense to only apply the rotational component,
> > and ignore scaling and translation ?
> > >
> > > Apparently there was some opiniated discussion around normal
> > > generation: http://seamless3d.com/hanim/hanim_with_hardware_shaders_
> > issues.html
> > >
> > > > Mix of skeletal and skinned bodies
> > > >
> > > > It is possible to have geometry both in the skin and the skeleton
> > (within segments) fields.
> > > > In this case it seems the full transform would be always applied to
> > the segment geometries. That may lead to out of sync movement during
> > animation but such mixed representation may not be intended to be fully
> > supported. How should an implementation deal with such humanoids ?
> > >
> > > May not be a priority to resolve.
> > >
> > > --
> > > Andreas Plesch
> > > Waltham, MA 02453
> >
> >
> >
> > --
> > Andreas Plesch
> > Waltham, MA 02453
> >
> > _______________________________________________
> > x3d-public mailing list
> > x3d-public at web3d.org
> > http://web3d.org/mailman/listinfo/x3d-public_web3d.org
> >
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-- 
Andreas Plesch
Waltham, MA 02453