[X3D-Ecosystem] Geometry nodes in Blender.

[John Carlson]

The reason I am focused on imports due to a WIP pull request I am being
asked to complete.   If someone would like to discuss how to import Jin
with segment and site geometry with animation,  we might make some progress.

I have not been able to import sites and segments as children of bones,
only armature.  That’s a huge problem.

I have not really gotten localized animations working well.

Thus I have been focusing on skinning.

John

On Fri, Dec 20, 2024 at 12:51 PM John Carlson <yottzumm at gmail.com> wrote:

> I can’t send my exported joe kick/skin due to file size and I’m attending
> my wife, so the computer is not an option.  Please share a link to the
> export file.  Thanks Joe.
>
> I shared the link to the .blend file in another message.  That’s what I
> think we should focus on, getting imports working first.  Since .glb
> blender exports are working, we can view the .glb in a number of tools.
>
> John
>
> On Fri, Dec 20, 2024 at 12:06 PM Joe D Williams <joedwil at earthlink.net>
> wrote:
>
>> Please look at John's export of joekick from blender. The skin binding
>> works fine except that it also includes all other geometry in the file as
>> skin so it  doesn't work quite right.
>> The problem in the exported file is that the 'standard' blender transform
>> node does not know about "center" and so it has to be added by a silly
>> USEage in blender to work.
>> Just fix blender (1) so it knows about center in a 'standard' Transform,
>> and (2) how it seems to include all geometry in the file, even children of
>> joints, as included in"skin" field and most all will be fixed.
>>
>> The idea of a bone center is not useful unless it is a joint. If a center
>> field is mentioned anywhere in blender it is in relation to a begin bone
>> end as some sort of crutch for having left center out of standard
>> Transform. Recall the days in 1998 when some tool makers were saying nah,
>> we don't need center in our transform object, translation, rotation, and
>> scale is plenty to expose except as special usage.
>> Thanks,
>> Joe
>>
>>  .
>> -----Original Message-----
>> From: Michalis Kamburelis <michalis.kambi at gmail.com>
>> Sent: Dec 20, 2024 2:07 AM
>> To: John Carlson <yottzumm at gmail.com>
>> Cc: X3D Ecosystem public discussion <x3d-ecosystem at web3d.org>, Vincent
>> Marchetti <vmarchetti at kshell.com>, Katy Schildmeyer KS APPAREL DESIGN <
>> katy at ksappareldesign.com>, Carol McDonald <cemd2 at comcast.net>, Joe D
>> Williams <joedwil at earthlink.net>
>> Subject: Re: Geometry nodes in Blender.
>>
>> > I think what you're saying is break a bone into 2 pieces, one with head
>> plus center (now tail) and one with center (now head) plus tail. This seems
>> like an excellent idea. I'm going to think on it a bit.
>> > My question is, what do I name the 2 pieces? I'm guessing something
>> that I can combine on export.
>>
>> Indeed.
>>
>> As for new bone names: "Leg1_center" (when you need to add new Blender
>> bone when "Leg1" joint has non-zero center in X3D/H-Anim) would look
>> reasonable for me (and code can figure out what happened and invert
>> it, so you can have round-trip that later exports it back into one
>> "Leg1" joint with non-zero center). But that's just a suggestion.
>>
>> > This sounds like Zeno's paradox where I'm just trying to put weights
>> where they don't go. The weights go on the joints. We only have weights for
>> joints on import. ((well, I don't know all of X3D).
>>
>> Weights describe how much each joint influences each vertex. This is
>> equal in Blender, X3D/H-Anim, glTF.
>>
>> I'm not sure if what you're saying is equivalent, but if yes -> OK :)
>>
>> > Remember I'm doing this in python, not in the Blender GUI.
>>
>> Sure, but it should be similar. That is, Blender's Python API exposes
>> a superset of things that you can do from GUI and it uses the same
>> terminology, mostly. And you can observe in Blender's console what
>> your interactive operation "means" in Python, it's a valid way to
>> learn Blender's Python API.
>>
>> > It sounds like I should give up on ever trying to import site or
>> segment geometry, and *try* to do Joints and skin.
>>
>> I'm not sure what do you mean here :)
>>
>> The H-Anim "skin" (one mesh, with joints and weights) should map to
>> Blender, because it is exactly the same concept in Blender. (OK, not
>> *exactly* the same, e.g. Blender, because of history, calls "bones"
>> what X3D/H-Anim and glTF call "joints"; but it is close to equivalent,
>> for 3D graphic artists these are the same things).
>>
>> You don't need to "give up" on anything, from what I can see. Just
>> import/export X3D/H-Anim skin to Blender's skin (Armature). This is
>> what 3D artists would expect.
>>
>> Other features (like attaching rigid objects to sites, without skin)
>> are a separate thing. They can be imported/exported e.g. as bones'
>> children. But these are separate things, I'd advise to focus on the
>> hard case (skin) first :)
>>
>> Regards,
>> Michalis
>>
>>
>>
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