[x3d-public] HAnim 2 X3DUOM...what is default?

[Joseph D Williams]

➢ … what the default value represents …

SITES:
Please look at part 1 annex B. The artwork illustrates the target locations for important surface features and reference measurement points of the humanoid. These are common body surface features used by a wide range of interchange. The tables in Part 1 Annex A lists a typical x y z location relative to 0 0 0 between the feet in the standard default pose. For hanim v2 we reused all v1 sites and added more from established work in other international humanoid interest groups. These human-scale measurements can be used to define a “standard” x3d hanim humanoid skin space. 

JOINTS: 
>From this skin space, the v1 team estimated appropriate joint center locations for the skeleton and located them in the same coordinate system using the same human scale in order to generate the “standard” list of skeleton joint center locations shown in the table of Part 1 Annex A. 

TOGETHER:
Combining the skin space and skeleton space models with some example animations then serves to completely validate the structure and function of the web3D x3d hanim character model. The humanoid can be built and animated in 5 levels of articulation to serve simple visual interactive transactions up to high fidelity kinematic simulations in immersive environments. And, since the x3d live scenegraph with internal/external SAI is the best, if not the best, realtime interactive data base, we have a great playground for hanim creations. 

So, to summarize, interested people made some progress from the mechanical armature to a programmable skeleton designed for interaction with other humanoids. They and us took the time to develop vrml and x3d until the hanim authortime can support human readable and highly transportable user code and a runtime that can use all of x3d and show the best of hanim versatility. 

Finally, now you can see that the skin space and skeleton space are distinct but stuffs gonna work best when the spaces are the same. Skeleton space is determined by the location of each Joint (itself an enhanced Transform node) center value. The effect of changing rotation value of a joint depends upon its function in the skeleton hierarchy. 
Likewise, the location of a surface feature also depends upon its position relative to 0 0 0 (can be considered in skin space but technically a style of user code can embed the Site location in Segment space). 

An example is if the skeleton is size fortyX relative to natural human space, then if you scale the skeleton to fit default scene space, and you have figured out how to do that with reasonable result, then you would set the Site locations in default scene coordinate space. If you did not rescale the skeleton natural human space, then the Sites would again be placed relative to skeleton space. 

Finally, the general recommendation for this is just draw the stuff in place relative to a “standard” humanoid using dimensions for your target character. If you have skeleton that is not dimensioned with respect to the natural scale, then change the joint centers to eliminate the need to somehow “scale the skeleton” to fit into a human-scale VR.

I hope this helps to lead you further into the fun of hanim. (For example, notice the default value for every Joint translation is by default and just works out right to be 0 0 0. The joint center value determines how it produces an effect on the hierarchy. For the Site, its location is set directly by its parent Segment and moves according to the parent Segment. The skeleton hierarchy is in Humanoid space but to scale the skeleton you must scale the Humanoid. If you scale the Humanoid, then you are scaling every contained space.) 

Thanks and Best, 
Joe




From: John Carlson
Sent: Wednesday, March 24, 2021 9:45 PM
To: Don Brutzman; X3D Graphics public mailing list
Subject: [x3d-public] HAnim 2 X3DUOM...what is default?

It would be most helpful if the default value in the enumerations in the 
HAnim concrete nodes in X3DUOM would some how inform the reader what the 
default attribute's value represents in the Humanoid (is it a center or 
translation for example).

Thanks!

John


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