[X3D-Public] [h-anim] [X3D] H-Anim WG, higher LOA considerations

Joe D Williams joedwil at earthlink.net
Fri Nov 15 15:07:34 PST 2013

This would be a nice picture. Keep in mind we also might want to be 
able to indicate surface features.

> - in essence, put sacrum at ...

The HumanoidRoot Joint is always at the center of the diagram.
Joint has Segment(s) and child Joint(s)
Segment has Site(s).
Segment can be bone.
Site is end-effector
LOAs defined by inclusion of Joint(s) and Site(s).

Even though a model 'flattened in 2D' is illustrative of the hierarchy 
I still think a 3D model (such as spec Illustrated example) is most 

The term 'flat' is interesting because even though you 'flattened' the 
model in order to show the connections, there is another meaning of 
"Flat" in relation to the humanoid.

This second definition of a 'Flat' skeleton would be that while the 
connections between the joints appear to show a heirerchy, the 'Flat' 
skelton does not work like the X3D skeleton hierarchy works. It has no 
kinematics. In the "Flat" skeleton, each joint is positioned 
independently of any others. I mention this again and again hoping 
somone will show me wrong just because the BVH data I have seen is 
meant to be applied to a "Flat' skeleton. I think Inverse kinematics 
will be required to make BVH style data sets work with the X3D 
hierarchal skeleton.

Best Regards,

----- Original Message ----- 
From: "Don Brutzman" <brutzman at nps.edu>
To: "Myeong Won Lee" <myeongwonlee at gmail.com>; <h-anim at web3d.org>
Cc: "Medical working group" <med at web3d.org>; "X3D Graphics public 
mailing list" <x3d-public at web3d.org>
Sent: Wednesday, November 13, 2013 7:54 PM
Subject: Re: [h-anim] [X3D] H-Anim WG, higher LOA considerations

> [cc: Medical & x3d-public for possible anatomical expertise]
> We are trying to build a better body and are trying to figure out 
> how to go from the current Level of Articulation (LOA) 0,1,2,3 out 
> to the full anatomically correct human skeleton.
> Attached is a diagram leading from our discussion today... further 
> informed by Kwan Hee Yoo's work to model high-definition face, hands 
> and feet as H-Anim additions.
> On 11/13/2013 6:28 PM, Don Brutzman wrote:
>> a further design enhancement, hoping to capture the questions 
>> better...
>> composability concern:  can different parts in different humans be 
>> combined, perhaps merged at a single common joint?
> if HAnimHumanoid node might begin by containing any HanimJoint, not 
> just sacrum, then different body parts might be composable at the 
> shared parent/child HanimJoint.
> I've always assumed that the sacrum Joint had to be the root.  It 
> would be tedious (and not very composable) if each body part had to 
> have a full skeleton linking it back to sacrum every time.
> We looked in the H-Anim specification and didn't find a specific 
> prohibition against other joints as the root...  could be there 
> though. Joe might know.
> http://www.web3d.org/files/specifications/19774/V1.0/HAnim/ObjectInterfaces.html
> http://www.web3d.org/files/specifications/19774/V1.0/HAnim/ObjectInterfaces.html#Humanoid
> "The skeleton field contains the HumanoidRoot Joint object.  The 
> Humanoid object is considered the parent object of the HumanoidRoot 
> Joint object and defines a coordinate space for the HumanoidRoot 
> Joint object.  Thus, the Humanoid object's transformation affects 
> the Joint object hierarchy in the skeleton field.  A hierarchy of 
> Joint objects is defined for each H-Anim humanoid figure within the 
> skeleton field of the Humanoid object and a hierarchical definition 
> of joints is present even when the geometry of the humanoid figure 
> is not defined within the skeleton field."
> Also found useful:
> http://www.web3d.org/files/specifications/19774/V1.0/HAnim/concepts.html#SkeletalHierarchy
> http://www.web3d.org/files/specifications/19774/V1.0/HAnim/concepts.html#StructureOfAHumanoid
> http://www.web3d.org/files/specifications/19774/V1.0/HAnim/concepts.html#Hierarchy
> which does define the complete hierarchy, including
> HumanoidRoot : sacrum
> Back to the diagram, going beyond the current limits of HAnim LOA 0 
> through 3:
> Dick insightfully observed that the dotted lines actually run back 
> to the center in this diagram.
> it would be very interesting to take the an LOA3 figure and
> - flatten it in 2D
> - spread out the node tree radially into respective circles for each 
> LOA, since they are all strict subsets
> - note what other other parts are still needed and where they go
> - in essence, put sacrum at center of attached diagram and propagate 
> the skeleton graph outward across LOAs
> Does anyone know of such a flattened skeleton, treating the joints 
> mathematically as a graph structure?
> 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 
> http://faculty.nps.edu/brutzman


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