[X3D-Ecosystem] Geometry nodes in Blender.

[John Carlson]

Why do I need to learn Blender?


https://youtu.be/ytomieYqUCQ
<https://youtu.be/ytomieYqUCQ?si=GXDiSTA6j3ZkUsID>

John

On Sat, Dec 21, 2024 at 12:11 PM John Carlson <yottzumm at gmail.com> wrote:

> I’ve moved discussion here to include others:
> https://projects.blender.org/extensions/io_scene_x3d/issues/64
> <https://projects.blender.org/extensions/io_scene_x3d/issues/64#issuecomment-1374368>
>
> On Sat, Dec 21, 2024 at 11:58 AM John Carlson <yottzumm at gmail.com> wrote:
>
>> 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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