[x3d-public] Units for BVH vs HAnimMotion.values

Sat Oct 14 12:34:07 PDT 2023

Wondering if you are reporting issues to Blender, John.

We found when writing the BVH import for X3D-edit that not all BVH files are formatted exactly the same, it was never standardized.

*	X3D-Edit 4.0 Authoring Tool for Extensible 3D (X3D) Graphics
*	https://savage.nps.edu/X3D-Edit
*	X3D-Edit is a free, open-source Extensible 3D (X3D) Graphics authoring tool for simple high-quality authoring, editing, import/export, validation and viewing of X3D scenes.
*	Suggested installation: install Apache NetBeans first, then install the X3D-Edit plugin.  Most reliable, you also will get notifications of updates automatically.

If you have a working BVH example that X3D-Edit has trouble handling and importing, then I’ll be happy to add corrections for that to our TODO list.  Thanks for all efforts.

all the best, Don

-- 

Don Brutzman  Naval Postgraduate School, Code USW/Br        brutzman at nps.edu

Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA    +1.831.656.2149

X3D graphics, virtual worlds, navy robotics https://faculty.nps.edu/brutzman

From: x3d-public <x3d-public-bounces at web3d.org> On Behalf Of Joe D Williams
Sent: Saturday, October 14, 2023 12:27 PM
To: John Carlson <yottzumm at gmail.com>; GPU Group <gpugroup at gmail.com>
Cc: x3d-public at web3d.org
Subject: Re: [x3d-public] Units for BVH vs HAnimMotion.values

> I’ve not had success with Blender Bvh import.

Success with blender would mean you have a blender skeleton that is animated by the bvh euler angle rotation data.

Don't even bother with Blender, maybe, because x3d does a documented conversion and the order of success is the same. The skeleton animated using the motion node directly may or may not actually convert to use interpolators. Or, the angle data is fully converted as shown to x3d syntax interpolator-driven animations used to control the skeleton. Just because the x3d player can use the bvh motion file doesn't mean it has to expose any x3d syntax. 

> is sufficient to imply Motion data is in degrees? Thee is no spec for bvh. Per part 2, if you have a file that looks like the descriptions, has the sample set of keywords and data structures, then give it a go. We also show how actually convert the file to x3d syntax if it is worth examining in detail. 

Joe

-----Original Message-----
From: John Carlson <yottzumm at gmail.com <mailto:yottzumm at gmail.com> >
Sent: Oct 14, 2023 8:00 AM
To: GPU Group <gpugroup at gmail.com <mailto:gpugroup at gmail.com> >
Cc: Joe D Williams <joedwil at earthlink.net <mailto:joedwil at earthlink.net> >, <x3d-public at web3d.org <mailto:x3d-public at web3d.org> >
Subject: Re: [x3d-public] Units for BVH vs HAnimMotion.values

I’ve not had success with Blender Bvh import.

John

On Sat, Oct 14, 2023 at 6:54 AM GPU Group <gpugroup at gmail.com <mailto:gpugroup at gmail.com> > wrote:

The Blender > Export/Import > mocap bvh code may have some hints.  

Hypothesis: on import it converts from mocap to interpolators, on export goes the other way.

Q. do you think that HAnim 5.2.4 Angle Conversion Procedure is sufficient to imply Motion data is in degrees? It doesn't mention the Motion node explicitly (Hypothesis written in an early era).. If so we could make the Motion.values degrees by default, as Joe suggested and 5.2.4 'indirectly implies'? 

-Doug

On Sat, Oct 14, 2023 at 2:47 AM John Carlson <yottzumm at gmail.com <mailto:yottzumm at gmail.com> > wrote:

Here's the Euler Angle to Axis-Angle in HAnim Pt section 5.2.4 

https://www.web3d.org/documents/specifications/19774/V2.0/MotionDataAnimation/AnimationUsingInterpolators.html#AngleConversionProcedure

Hmm!  I'm guessing that Blender has a routine for this! Sure enough!  Trying it now.

Not with HAnimMotion, I don't know how to do that yet.  Suggestions?

John

On Sat, Oct 14, 2023 at 12:21 AM Joe D Williams <joedwil at earthlink.net <mailto:joedwil at earthlink.net> > wrote:

> Um, then why is angle even listed here?

That is easy, take another look. 

Euler angles are not listed anywhere! 

Convert to axis-angle like showed in Part 2 and forget xyz angles/

Joe

-----Original Message-----
From: John Carlson <yottzumm at gmail.com <mailto:yottzumm at gmail.com> >
Sent: Oct 13, 2023 6:15 PM
To: Joe D Williams <joedwil at earthlink.net <mailto:joedwil at earthlink.net> >
Cc: <x3d-public at web3d.org <mailto:x3d-public at web3d.org> >
Subject: Re: [x3d-public] Units for BVH vs HAnimMotion.values

Um, then why is angle even listed here? 

Confusing as heck!

https://www.web3d.org/documents/specifications/19775-1/V4.0/Part01/concepts.html#t-Standardunits

John

On Fri, Oct 13, 2023 at 7:19 PM Joe D Williams <joedwil at earthlink.net <mailto:joedwil at earthlink.net> > wrote:

> otherwise specified in a UNIT statement 

https://www.web3d.org/documents/specifications/19775-1/V4.0/Part01/concepts.html#Standardunitscoordinates

"However, the world coordinate units may be modified by specifying a different length unit using the UNIT statement."

There is Not Now nor will there Ever be a UNIT statement that allows degrees for rotation and orientation. 

Never, will angles appear in any x3d animation interpolator. 

To apply an import using angle units, it is converted to x3d before use, then discarded or possibly stored somewhere away from working area for reference.  

Thanks and Best,

Joe

-----Original Message-----
From: John Carlson <yottzumm at gmail.com <mailto:yottzumm at gmail.com> >
Sent: Oct 13, 2023 11:44 AM
To: X3D Graphics public mailing list <x3d-public at web3d.org <mailto:x3d-public at web3d.org> >
Subject: [x3d-public] Units for BVH vs HAnimMotion.values

Apparently BVH uses degrees for rotations.  Units for HAnimMotion should use radians unless otherwise specified in a UNIT statement, AFAIK. 

Comments?

Thanks!

John 

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