[x3d-public] Negative scale only allowed in Transform, not HAnimHumanoid,

[Brutzman, Donald (Don) (CIV)]

Joe, am noticing that negative scale is allowed for Transform but not for HAnimHumanoid.  This issue was uncovered via recent improvements to X3DJSAIL model checking, which flagged the error in your HAnimHumanoid representations for Tufani et al.

 

*	X3D 4.0 Architecture, 10 Grouping component, 10.4.4 Transform
*	https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-IS.proof/Part01/components/grouping.html#Transform

 

Transform : X3DGroupingNode {

 

  SFVec3f    [in,out] scale    1 1 1    (-∞, ∞)

 

*	X3D 4.0 Architecture, 26 Humanoid Animation (HAnim) component, 26.3.2 HAnimHumanoid
*	https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-IS.proof/Part01/components/hanim.html#HAnimHumanoid

 

HAnimHumanoid : X3DChildNode, X3DBoundedObject {

 

  SFVec3f    [in,out] scale    1 1 1    (0,∞)

 

I think that these are good limits on the scale fields.  Negative-scaling transformationof arbitrary geometry is a well-understood use case.  However a humanoid must be internally consistent, using the default X3D right-hand rules, if we are going to use interchangeable behavior animations with it.

 

You might validly apply negative scaling via a Transform parent over the HAnimHumanoid, but (for Superman fans) that might only be workable in a Bizzaro mirror-backwards universe…  No thanks, don’t want to go there.

 

I recommend fixing the geometry in the model definition to be right handed, either via adjustment of the original export, or else postprocessing of the geometry you have.

 

Conceivably such operations might be candidate future functionality for the X3D Tidy stylesheet – pretty tricky however.

 

*	X3D Tidy for Scene Cleanup, Corrections and Modifications
*	X3D Tidy is an XSLT stylesheet that checks for simple authoring difficulties in X3D scenes and fixes them.
*	https://www.web3d.org/x3d/stylesheets/X3dTidy.html

 

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

 

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