[X3D-Ecosystem] Geometry nodes in Blender.

[John Carlson]

The trick on export is to traverse the non-bone joint+ hierarchy, and get
the bone_parent to retrieve the bone head (joint center).  Then I look up
the vertex groups from the bone name to get the weights and coordIndexes.

Now the question is, do I put animations on bone joints or non-bone
joints.  I think bone joints is best.  So when I traverse the non-bone
hierarchy, I ignore empties that are joints, and do any animation on
transforms or sites (which carry the mesh).  I am not aware that I can
animate segments.  I still am not convinced that I’ll be able to
distinguish Sites and Segments from Transforms on output.  I guess segments
are direct children of joints.

On Sat, Dec 21, 2024 at 9:26 AM John Carlson <yottzumm at gmail.com> wrote:

> In summary, on Blender import, to enable x3d transform animation, I have
> to create empty objects.   To enable skin weights, I need bones. That means
> 2 hierarchies because armature has 2 hierarchies, one empties, etc, and one
> bones.  We can’t multiply out the transform hierarchy and set matrix world
> like we do in production because of transform animation.  I agree, it’s
> super simple without animation.
>
> Some collada models expect the matrixes to be multiplied out on x3d
> reimport and have hierarchical meshes. They don’t have animation.  Please
> provide collada models with animation.  We might be able to fix x3d export
> here if someone tells me how to handle hierarchical meshes.  In general,
> all objects in blender have transforms, so this needs to be thought out.
> Primarily, I think, each x3d object equivalent will have a transform and a
> shape on export. I don’t know how I’m going to convert empties to sites and
> segments except by name.  I think that’s implemented, I forget if I
> disabled it or it’s not available on import.  This is one reason why the
> exporter is in flux.  We probably can create an option on export.
>
> Some models have both skin and segments. We need segments to support sites.
>
> Do we want animation import?  What I can probably do is detect animation
> and  turn on hierarchical loading.
>
> At this point, OpenUSD looks super attractive if they opened up the .usda
> grammar.  AFAIK, every prim has a matrix.
>
> If someone has a snapshot of an object attached to a parent bone in the
> blender hierarchy, that would be super helpful.
>
> John
>
>
>
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