[x3d-public] X3D Working Group meeting 23 SEP 2022: Mantis issues review, ballot deadlines, X3D Application Stack Layer Examples diagram

Fri Sep 23 11:43:20 PDT 2022

Attendees: Dick Puk, Don Brutzman

1. We first reviewed the two recently posted Mantis issues regarding SVG and
QIF.  We also looked at a Mantis issue posted earlier this year relating to
scalable composition of really large X3D worlds.  Selected details follow.

a.	Mantis 1400: add Scalable Vector Graphics (SVG) to recommended image
formats for ImageTexture

https://www.web3d.org/member-only/mantis/view.php?id=1400

SVG references:

*  <https://www.w3.org/Graphics/SVG> https://www.w3.org/Graphics/SVG
* "SVG is a markup language for describing two-dimensional graphics
applications and images, and a set of related graphics script interfaces."

Dick estimation: thinks SVG is a 2D scene-graph definition language. It can
result as an image, though so can X3D.

This issue suggests that SVG be listed as a recommended (optional) format
that can be rendered as an ImageTexture, using the default presentation
settings of the SVG model.

Of note is that browsers are not forbidden from implementing SVG as an
ImageTexture format, and also that SVG-to-PNG converters are commonplace.

Of further note is that the DPS minutes already showed a use case for SVG as
ImageTexture, namely conversion of metadata information as a carefully
laid-out annotation image that is billboarded in context. Having direct SVG
rendering would eliminate the offscreen conversion step, permitting direct
integration of X3D models with other HTML/SVG web graphics.

Concern: don't want to overcomplicate the existing ImageTexture
functionality as a 2D array of pixels. Once generation of pixels becomes a
computational process, this is different functionality for the ImageTexture
node. This might raise further concerns about impact of ImageTexture
computational complexity in various profiles (such as Interchange Profile).

Possible alternate: define SvgTexture node? What fields would it have?

Suggested possible resolution:

a. Browsers are welcome to implement ImageTexture as an allowed url format
if they see fit,
b. SvgTexture ought to be designed and considered as a possible new node,
c. ComposedImageTexture (or somesuch) might be designed and considered as an
even-more general possibility for comuputational 2D imagery,
d. Following further practical experience, defer any specification-change
recommendations to future X3D4.1.

b.	Mantis 1401: aligning X3D4 LineProperties with Quality Information
Framework (QIF) specification

https://www.web3d.org/member-only/mantis/view.php?id=1401

Suggested resolution:

a. The concepts are directly aligned and overlapping, with some additions by
QIF.
b. This ISO standard does not appear to have been considered by SC24 or
JTC1.
c. Close scrutiny of both terms and definitions needs to be performed before
any changes might be recommended.
d. If changes are indeed warranted and acceptable, then they likely need to
first considered as part of the Registry of Items, specifically entries for
linestyle and hatchstyle.
e. At that point, amendment of X3D to stay aligned with Registry of Items
(or possibly add further styles independently) can be considered.
f. Defer to X3D 4.1.

Meanwhile note in Web3D current ballot comments the need to fix the table
erratum previously noted.

c.	Mantis 1192: 07.2.2 Bindable children nodes - Undefined results if
bindable node is under Switch or LOD is problematic

https://www.web3d.org/member-only/mantis/view.php?id=1192#bugnotes

Comment on 19775-1: Abstract X3D Definitions - V3.3
7.2.2 Bindable children nodes

<http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/component
s/core.html#BindableChildrenNodes>
http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components
/core.html#BindableChildrenNodes

-----------------
Subject: Undefined results if bindable node is under Switch or LOD is
problematic

Spec sayeth:
"The results are undefined if a bindable node is bound and is the child of
an LOD, Switch, or any node or prototype that disables its children."

This leads to all manner of inconsistent problems among scenes. It also
means that Inline node (which may or may not include bindable nodes) has
undefined behavior under LOD/Switch/etc.

As a result, in addition to indeterminate X3D browser behavior, it means
that X3D scenes are not fully composable. That is contrary to X3D design
objectives.

Different prose and deterministic guidelines is needed in this section that
provides clear rules for binding/unbinding nodes when they become active
within LOD/Switch/etc. Small adaptations to current binding rules can likely
address this problem satisfactorily.

Related: Mantis issue 749

April 29:

Analysis during X3D Working Group call:

a. Switch would keep each binding stack aligned with whichever child was
active, thereby binding and unbinding nodes whenever the Switch level is
modified.

b. LOD would have all of its child bindable nodes on the binding stack
throughout, so that user experience was consistent. For example, it would
make no sense for Viewpoints to get arbitrarily unbound and bound, based on
range to viewer, as a user independently navigated through a scene.

c. LOD attempting to maintain author intent has access to all Viewpoint
nodes on binding stack, and range-to-viewer LOD transitions are either
flexible suggestions (browser-optimization control) or rigidly enforced
(forceTransitions field is TRUE). Thus if a node is subsequently bound by
user in a different inactive LOD child branch, then that binding event is
honored and that LOD child branch becomes the active child branch. This
binding event (and changed LOD child branch selection) takes precedence over
browser range/performance considerations, and also takes precedence over
whatever value is provided in forceTransitions field. (Example: selecting a
room Viewpoint while in a large building model).

d. NavigationInfo, Background and Fog binding stacks and responses to
binding events should behave identically to Viewpoint. Variations would be
exceedingly complex and not understandable. Consistency means that author
intent and user action always take precedence, for Switch and LOD response.

Spec editors work on integrating these principles as specification prose (we
are close already) and report back recommended changes to X3D working group.

Don's opinion: this will significantly help user-sensible scalability of
huge (perhaps Metaverse-scale) models using many Inline and prototype nodes,
enabling predictable and performant navigation and traversal throughout.

Today's session.

Alternatives deserving working-review consensus:

a. Recommending this clarification of undefined prior specification prose
might add important value, or might be construed as a technical change to
X3D4.0 that possibly requires future re-balloting as another X3D 4.0 DIS
(which is not an acceptable outcome).

b. If not balloted then this becomes an X3D4.1 issue.

c. Web3D might consider some alternative approach to strongly encourage
adoption of this clarified approach in order to further encourage greater
scalability of multi-world environments, and better alignment with shared
Metaverse design imperatives. For example, are we creating a Best Practices
Pending X3D 4.1 Approval document of some sort?

2. We only have 4 total issues to review as planned Web3D comments.  This
will occur during a single working-group meeting, 7 OCT.

Deadline for X3D Ballot comments:

*	OCT, Web3D comments to INCITS (U.S. National Standards Body
*	TBD OCT, INCITS comments to SC24
*	4 NOV, SC24 comments to ISO

No meeting currently planned for 30 SEP.

3. Bonus round: we worked on the "layer" diagram from recent meetings a bit
more.  Latest X3dApplicationStackLayerExamples is attached, all comments
welcome.

Have fun with X3D!

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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://web3d.org/pipermail/x3d-public_web3d.org/attachments/20220923/09b52ac5/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: X3dApplicationStackLayersAlternatives.png
Type: image/png
Size: 57035 bytes
Desc: not available
URL: <http://web3d.org/pipermail/x3d-public_web3d.org/attachments/20220923/09b52ac5/attachment-0001.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 5353 bytes
Desc: not available
URL: <http://web3d.org/pipermail/x3d-public_web3d.org/attachments/20220923/09b52ac5/attachment-0001.p7s>