[x3d-public] HAnimDisplacer effect on coord.point

[Andreas Plesch]

Don, Joe and John

Thanks for collecting these references.

But I am not sure if there is an answer to my original question. Let me
rephrase a bit the question:

After a Displacer contained in a Segment node receives a set_weight input,
should then the coord node emit a point_changed event ?

I do not think HAnim is concerned about that, so it is really a X3D
question.

Thanks, Andreas

On Sun, Feb 9, 2025, 12:49 AM Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
wrote:

> 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> 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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