[x3d-public] HAnimDisplacer effect on coord.point

Sat Feb 8 21:49:53 PST 2025

Thanks for pointing in the right direction John.

Direct links to functional requirements for Displacer in HAnim 2.0 specification:

  *
HAnim 2.0. Part 1:  Humanoid animation (HAnim) architecture, Clause 4 Concepts, 4.7 Displacer object
  *
https://www.web3d.org/documents/specifications/19774/V2.0/Architecture/concepts.html#DisplacerObject

  *
HAnim 2.0. Part 1:  Humanoid animation (HAnim) architecture, Clause 6 Object interfaces, 6.6 Displacer
  *
https://www.web3d.org/documents/specifications/19774/V2.0/Architecture/ObjectInterfaces.html#Displacer

and

  *
X3D 4.0 Architecture, Clause 26 Humanoid Animation (HAnim) component, 26.3.1 HAnimDisplacer
  *
https://www.web3d.org/specifications/X3Dv4/ISO-IEC19775-1v4-IS/Part01/components/hanim.html#HAnimDisplacer

and informative

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

Thanks for implementation efforts and careful scrutiny.

Questions and potential issues/clarifications/corrections are always welcome.

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 John Carlson via x3d-public <x3d-public at web3d.org>
Sent: Saturday, February 8, 2025 3:43 AM
To: Extensible 3D (X3D) Graphics public discussion <x3d-public at web3d.org>; Carol McDonald <cemd2 at comcast.net>; Joe D Williams <joedwil at earthlink.net>
Cc: John Carlson <yottzumm at gmail.com>; Andreas Plesch <andreasplesch at gmail.com>
Subject: Re: [x3d-public] HAnimDisplacer effect on coord.point

Here’s what HAnim spec says under Displacer:

https://www.web3d.org/documents/specifications/19774/V2.0/index.html

“For the Displacer objects that are contained in the displacers field of the Segment objects, the displacements are defined and applied in the Segment coordinate system. The base mesh for the morphed Segment is the original mesh defined in the Segment.”

And here’s what it says under Segment:

“

The coord field is used for Segment objects that have deformable meshes and shall contain coordinates referenced from the indexed mesh for the Segment object. The coordinates are given the same name as the Segment object, but with a "_coords" appended (e.g.,"skull_coords").”

displacements are an offset from the mesh,  with weight from 0 to 1.  So weight times displacement is total offset from base mesh.  0 weight = no offset, 1 weight = full displacements offset

The Coordinate point is maintained to handle weight = 0.  Weight ranges from 0 to 1, but double check.

Joe or Carol might know where to find it in the HAnim spec.

I believe the answer is, “during rendering,”. Since weight can vary with animation, and so can displacements, AFAIK.  More than one displacer can be applied to the mesh.

I have not read the spec.

John

On Sat, Feb 8, 2025 at 5:13 AM Andreas Plesch via x3d-public <x3d-public at web3d.org<mailto:x3d-public at web3d.org>> wrote:
https://www.web3d.org/documents/specifications/19775-1/V4.0/Part01/components/hanim.html#HAnimDisplacer

does not directly explain what the effect of the displacer on the coord.point field of the containing HAnimSegment is. But it mentions the coord.point field and seems to imply that the coord.point field is involved.

So the question is if the Displacer should alter the coord.point field in order to achieve a graphical displacement, or if the Browser should only apply the displacements during rendering without a change in the coord.point field ?

This is relevant if the coord.point field is accessed by routes or scripts, in addition to displacers.

Thanks for any feedback or ideas,

Andreas

--
Andreas Plesch
Waltham, MA 02453
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