[x3d-public] HAnimDisplacer effect on coord.point

[John Carlson]

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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>
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