[x3d-public] What is "loa" ?

[Don Brutzman]

MUFTI you definitely want to be looking at the HAnim2 specifications.

Web3D Consortium members are the controlling authority for X3D and HAnim specifications, International Standards Organization (ISO) certifies.

X3D3 is simply implementing HAnim2, typically as tersely as possible so that there is no confusion in prose that HAnim2 is the controlling specification.  Please see

* ISO/IEC 19774-1, HAnim2 Specifications parts 1 and 2
   https://www.web3d.org/documents/specifications/19774/V2.0/

===============================================
* ISO/IEC 19774-1, HAnim2 Specifications part 1
   clause 3 Terms and definitions
   https://www.web3d.org/documents/specifications/19774/V2.0/Architecture/glossary.html

3.11
   level of articulation
   LOA
   degree of fidelity based on number of joints in an HAnim figure
===============================================

also

* 4.8.5 Levels of articulation
   https://www.web3d.org/documents/specifications/19774/V2.0/Architecture/concepts.html#LevelsOfArticulation

"Level of articulation (LOA) represents the complexity and detail of joints for a humanoid skeletal hierarchy, and can be used for generating various motions based on the joints. There are five levels of articulation:

     LOA‑0 represents only the humanoid_root Joint object without an accompanying hierarchy, as shown in (Figure 4.3).
     LOA‑1 represents the simplest organization and hierarchy of joints for a humanoid. There are 18 joints and 18 segments. Each segment has a joint in the hierarchy. Figure 4.4 represents LOA‑1 joints.
     LOA‑2 consists of 71 joints and 71 segments (Figure 4.5).
     LOA‑3 consists of 94 joints and 94 segments (Figure 4.6).
     LOA‑4 builds on LOA‑3 by adding anatomical details of hands and feet (Figure 4.7). LOA‑4 consists of 148 joints and 148 segments. Hands and feet joints for LOA‑4 are illustrated in 4.9.3 and 4.9.4 respectively."


* 4.9 Structure of a humanoid, 4.9.6 Hierarchy
   https://www.web3d.org/documents/specifications/19774/V2.0/Architecture/concepts.html#Hierarchy

* 4.9 Structure of a humanoid
   https://www.web3d.org/documents/specifications/19774/V2.0/Architecture/concepts.html

* Annex A (informative) Nominal human body dimensions and levels of articulation (LOAs)
   Nominal human body dimensions and levels of articulation (LOAs)

* A.2 Levels of articulation (LOAs)
   https://www.web3d.org/documents/specifications/19774/V2.0/Architecture/BodyDimensionsAndLOAs.html#LevelsOfArticulation

There is a lot of information in there that deserves careful reading.  You will find tables and diagrams that illustrate every joint and (bone) segment in the human body, along with a number of useful feature-point sites.  This took years of effort by many members of HAnim working group.

Current work by Joe Williams, John Carlson and myself is improving past-legacy examples to match HAnim2 capabilities with X3D4.  We hope that testing and verification will help.

* HumanoidAnimation X3D Examples Archive
   https://www.web3d.org/x3d/content/examples/HumanoidAnimation

* X3D Tooltips, HAnimHumanoid loa
   https://www.web3d.org/x3d/content/X3dTooltips.html#HAnimHumanoid.loa

HAnim designers hope that by identifying both HAnimHumanoid models and HAnimMotion animations with the LOA supported, it will be easier to mix/match models and animations.  Since each LOA is a strict subset of the next LOA, some compatibility is possible across human LOA levels.

* 4.9.7 Site and Segment relationships
   https://www.web3d.org/documents/specifications/19774/V2.0/Architecture/concepts.html#SiteSegmentRelationships

It is not impossible to think that someday this work might even rise to the level of rigor needed for 3D HAnim models becoming part of medical records.  HAnim and X3D4 have the potential to help... everyone.

Thanks for your scrutiny and helpful questions.


On 6/18/2020 11:02 PM, John Carlson wrote:
> 
> To answer your question, many parts of the government like to create acronyms.
> 
> John

Sorry John, can't blame government for this one.  (Wondering, are parts of the government controlling your keyboard?!)

> On Fri, Jun 19, 2020 at 12:38 AM J. Scheurich <mufti11 at web.de <mailto:mufti11 at web.de>> wrote:
> 
>     hI,
> 
>     From
> 
>     https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD1/Part01/components/hanim.html#HAnimMotion
> 
>     SFInt32 [in,out] loa -1 [-1,4]
> 
>     What does "loa" mean ? Fieldnames in X3D are often english words,
>     but the dictionary leo.org <http://leo.org> has no results for "loa" 8-(
> 
>     so long
>     MUFTI
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