[x3d-public] X3D, Blender, and which way is up.

[John Carlson]

Primarily, currently, my skin imports with standard Blender conventions,
and the armature with another.  I think this primarily because I imported
joint centers without any center transforms or matrix settings for the
Blender bones.

If I apply skin weights, the skin becomes elasticman.  This is also due to
animations at frame=0 away from I-pose, which makes it difficult to do
auto-rigging.

John

On Sun, Nov 24, 2024 at 2:38 PM John Carlson <yottzumm at gmail.com> wrote:

> Yes, Vince.  There’s definitely issues with my HAnim importer after
> including recent changes to the Blender importer.
>
> Please check the Discussion on the Blender extension site.
>
> Ideally, we would have something that would work with any coordinate axes
> the user selected.
>
> John
>
> On Sun, Nov 24, 2024 at 1:40 PM vmarchetti--- via x3d-public <
> x3d-public at web3d.org> wrote:
>
>> I've seen that the email thread starting with the minutes of the last
>> Blender-X3D support call had a subthread about the orientation conventions
>> that glTF, Blender, and X3D use.
>>
>> I recommend Michalis' answer at
>> https://web3d.org/pipermail/x3d-public_web3d.org/2024-November/020882.html
>> .
>>
>> One confusing aspect is that not only do Blender and glTF disagree about
>> which axis is forward, they disagree about what the word "forward" means.
>>
>> For Blender, the word "forward" refers to the axis that the viewer is
>> looking along when they are viewing the front of the model.
>> The viewer is translated from the model in the -Y direction, and they are
>> looking in the +Y direction. That, +Y,  is Blender "forward"
>>
>> glTF defined "forward" by the model.Looking at the first sentence of the
>> of section 3.4 of the glTF specification.
>> https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#coordinate-system-and-units
>> ,
>>
>> glTF uses a right-handed coordinate system. glTF defines +Y as up, +Z as
>> forward, and -X as right; the front of a glTF asset faces +Z.
>>
>>
>>
>> glTF says the "forward" refers to the direction the asset, a.k.a. model
>> is facing and the spec shows this example picture . In Blender terminology
>> this model is oriented "-Z forward"
>>
>>
>>
>> [image: boombox.png]
>>
>> The X3D standard has the same orientation convention as glTF, by virtue
>> of the X3D default placement of the Viewpoint at a Z=+10 position and
>> looking in the -Z direction. That is why in Blender terminology the X3D
>> convention should be considered -Z forward. The code in the Blender
>> extensions server was changed to this default for X3D import and export on
>> Nov 4 2024 and this default is in release 2.4.0 of this Blender extension.
>>
>> Vince Marchetti
>>
>>
>>
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>>
>
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