[X3D-Public] X3D Followers meeting Wednesday please

Don Brutzman brutzman at nps.edu
Wed Feb 8 09:04:14 PST 2012

We had a productive Followers review call today by Herbert Stocker and I.

On 2/6/2012 9:08 AM, Don Brutzman wrote:
> Some minor but longstanding action items are to address comments on
> the Followers (chasers and dampers) component.  Herbert, we need your
> feedback please.
> Primary points:
> - shouldn't there be a ScalarDamper node to correspond to ScalarChaser?
> 	(InstantReality has also implemented this)

Details follow.

Instant reality

We also looked at their other proposed nodes:

InstantReality Followers
    PositionChaser3D (alternate name for PositionChaser)
    PositionDamper3D (alternate name for PositionDamper)

X3D specification, Followers component, 39.4 Node reference

    39.4.1 ColorDamper
    39.4.2 CoordinateDamper
    39.4.3 OrientationChaser
    39.4.4 OrientationDamper
    39.4.5 PositionChaser
    39.4.6 PositionChaser2D
    39.4.7 PositionDamper
    39.4.8 PositionDamper2D
    39.4.9 ScalarChaser
    39.4.10 TexCoordDamper2D

Diff list:
    TexCoordChaser (if defined, X3D name would be TexCoordChaser2D)

A reasonable argument could be made that consistency of support
for both Chaser and Damper ought to provided for each data type.

Herbert didn't think it would be difficult for BitManagement to
also implement these 4 additional nodes.  He has no object to adding
these nodes.

I'm willing to add them to X3D-Edit to match.

Any other implementers have an opinion?

We discussed whether it would increase the burden for browser implementers.
Since any implementation of 10 existing nodes in Followers component includes
each of these data types, and since it also includes both Chasers and Dampers,
and since the algorithms are essentially identical in each case, the level of
difficulty is very low.  Further we could say that since the animation
algorithms are quite simple, these 4 nodes do not appreciably increase the
size of a plugin implementation.

Therefore, subject to group approval, we recommend that these 4 nodes be added
to X3D.

Action items for InstantReality would be to
- rename TexCoordChaser to TexCoordChaser2D (to match proposed change)
- rename TexCoordDamper to TexCoordDamper2D (to match existing X3D spec)

Dick:  Web3D will likely want to recommend making this change as part of
the X3D version 3.3 ISO review.  This might be considered to be errata
since the changes provide proper consistency to the Followers component.
Let's please discuss our options on the next working group teleconference.

> - getting consistent browser support for example scenes
> 	http://www.web3d.org/x3d/content/examples/Basic/Followers/

We reviewed these examples.  Some work but many don't in BS Contact.
Most of the scenes were my translations of Herbert's original examples,
which used a preliminary node syntax developed prior to approval of the
X3D Followers Component.

Herbert can check on BS Contact support and whether the example scenes
are correct or not.  I will fix any scene problems and check the updates
back into version control.  For test purposes we might implement
CoordinateChaser as a native node (instead of using a prototype),
if others in X3D group agree that this addition to the spec is likely.

We will both work to revisit this topic in 2 weeks during the
teleconference 22 FEB 2011.  All feedback 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 http://faculty.nps.edu/brutzman

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