[x3d-public] X3D minutes 4 OCT 2019: X3D-glTF review, defer Annotations, Layout component, #X3Dv4 implementations/issues update

Brutzman, Donald (Don) (CIV) brutzman at nps.edu
Fri Oct 4 09:56:39 PDT 2019

The X3D Graphics Working Group addresses all X3D specification issues and coordinates the technical development of future improvements.

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Attendees: Anita Havele, Vince Marchetti, Nicholas Polys, Dick Puk, Don Brutzman.

1. Agenda check: looks good.


2. *glTF*. Any questions from last week, minutes looked like excellent discussion/progress on X3D loading glTF.
	[x3d-public] Summary of X3D 4 specification changes related to PBR and materials

	[x3d-public] X3D agenda 27 SEP 2019: glTF PBR/lighting, DICOM OBJ

One long-running discussion point is the comparison of glTF and X3D lighting.  Here is a candidate summary.

a. glTF Lighting Extension defines three lights, Directional Point and Spot, which only define color.  These are simply defined, e.g. geometric aspects but only a single color value.

b. Meanwhile Physically Based Rendering (PBR) requires more sophisticated parameters, which are included in core glTF material properties but do not have corresponding light assets defined.  It seems that glTF implementations are allowed to have custom lighting parameters.  This explains why some rendering comparisons of glTF models appear to be rendered differently by different tools.

c. Note that X3Dv3 classic lighting model does include some additional color parameters (diffuse color, ambientIntensity).

	X3D draft, 17 Lighting component

d. X3DOM, X_ITE and CastleGameEngine have worked on implementing the advanced PBR capabilities.  We are looking forward to the detailed analysis by Michalis Kamburelis to be distilled as an updated lighting model for X3Dv4.

	X3DOM glTF examples - PBR Tests - these are quite extensive!
	(Suzanne image attached)

	X_ITE documentation: IndexedTriangleSet shows conversions of glTF to X3D for PBR
	(scroll down to example scene) which were perhaps converted using Titania?
	(conversions could be integrated into player, presumably) we'll invite Holger to a future meeting.

	Castle Game Engine: references provided separately

e. We expect to have corresponding additions to X3D Lighting Component to provide well-defined support for precise consistent rendering of glTF models in X3D, as well as explicit rendering of X3D Shape geometry using the same advanced PBR appearance capabilities.  By default we expect that X3Dv4 will default to "classic" X3Dv3 lighting, that scenes can explicitly set PBR rendering for shapes, and that both "classic" and "PBR" rendering can coexist in a single X3D scene.

f. Khronos experts have agreed to review and comment on whatever we produce in order to ensure compatibility and consistency.

Follow-on TODO: update feature-comparison table. Would anyone like to lead this review update?

> * Attachment [3]: glTF X3D Features Comparison (3 NOV 2017)
>    https://www.web3d.org/sites/default/files/page/X3D%20Version%204%20Strategy/glTfX3dFeaturesComparison.pdf
> * source at
>    https://docs.google.com/spreadsheets/d/12ebxqfQoFPuNhaz8wZkNE6G-w_bqt98iy6p5F9IazVM/edit#gid=0

Nicholas has a draft blog entry on this important subject.  Feedback is welcome:

	Integrating X3D and GLTF


3. *Annotations*.  Review Annotations component modifications posting, see if it is understood

	[x3d-public] X3Dv4 Annotation Component revision, request review

> Refinement of key questions:
> a. What is the scope of an annotation?  Does it affect it's parent, i.e. peers and their childen?  For example, how would you annotate an IFS if the annotation can only get inserted into scene graph as a peer of the containing Shape node?
> b. Can we move url field to 42.3.1 X3DAnnotationNode and then omit 42.4.6 URLAnnotation?  This refactoring would simply overall design, and allow any annotation to be either local (children) or external (via url).
> c. Text annotation might be plain text, styled text (HTML fragment or possibly markdown), XML, etc.
> d. Can we better rename 42.4.3 GroupAnnotation node as InlineAnnotation or ModelAnnotation?  (The name GroupAnnotation is ambiguous and seems to imply that it is grouping annotations themselves.)  Note this is directly related to scoping question.
> e. Can we better rename 42.4.4 IconAnnotation as ImageAnnotation? (The term "icon" implies characteristics such as small size or mostly square, but the node had no such restriction.)
> f. Examples are definitely needed.  Prototypes are certainly possible here to show node design working coherently.
> g. Conceivably this might be legitimately deferred to X3Dv4.1 because correct use of annotations is quite important in XR and MAR contexts.  But it seems close and if done right, the annotations would work satisfactorily with any user-interface modality.

Nicholas points out that a lot of things have changed since then, and there are big issues that need to be addressed in a more coherent and complete fashion.  There are more use-case requirements than are documented.
- As one prominent example, what about HTML and markdown and XML and JSON?
- As another prominent example, Smithsonian has three annotation types that are simple/different/useful.
- As a third example, what about annotations to external HTML browser?
- As a fourth example, what about when an annotation targets a portion of a single mesh?  Or a single point, or a group, or a geospatial location?

We need to push this component back to a baseline reconsideration of requirements, use cases and exemplars.  This should all be deferred as future work, better and more appropriate in X3Dv4.1 when we are looking specifically at VR/AR/MAR.  It would also benefit from having well-defined relationship between HTML5 and X3Dv4 (for another example, coordinate space definitions would be clearer).  There are many historic examples of various layout toolkits and GUI architectures that made good limited progress but did not resolve all needs consistently.

Certainly refactoring is possible - Nicholas described one.  Could this reconsideration be an objective for nascent UX working group?  Perhaps the problem space is too broad, and thus better better to wait?  Of note is that all the working groups have an interest in this work being done correctly.  Accessibility, usability and W3C ARIA are additional related domains...  there is quite a lot to consider.  Perhaps this work will be suitable for someone to consider a workshop proposal.

There are no other strict dependencies on this draft component elsewhere in the X3D specification.

*We agreed to defer Annotation Component as future work, not as a part of X3Dv4 specification.*

Related note: Feng Liu has proposed starting a Web3D User Experience (Web3dUX) working group.  This topic will be reviewed over there.

	Mondays 09-1000 pacific (12-1300 eastern) following X3D Semantic Web Working group call.
	entries on Web3D Calendar and Web3D Teleconference page (same links as semantic call).

Related annotation work by Leonard Daly

Important related research work, multiple explanatory assets attached:
	Nicholas F. Polys, Virginia Tech, dissertation, 2006
	"Display Techniques in Information-Rich Virtual Environments"


4. *X3D Implementations*. Review and update page.

	X3Dv4 Implementations Status

a. PointProperties implementation efforts continue in the Design Printing Scanning working group.  Looks like a good spec but we want to encourage multiple consistent implementations.  Slightly tricky since points are hard to capture visually.

b. Layout component has been identified for deprecation but there has been implementation work.


- X_ITE has implemented Layout component: Layout,LayoutGroup,LayoutLayer,ScreenFontStyle,ScreenGroup


- Janek Jankowski has relevant papers on this topic and annotation considerations, including the following:


	The 2LIP model and its implementations,2009
	2LIPGarden: 3D hypermedia for everyone,2009
	2lip: Filling the gap between the current and the three-dimensional web, 2009

Proposed next steps:
- identify proper example scenes,
- evaluate them in X_ITE (and any other implements),
- consider whether overlaps with HTML5 are acceptable or difficult/problematic, then
- formally decide whether to deprecate or encourage consistent adoption.

c. Looking ahead: there are two threads ongoing in X3DOM and X_ITE regarding textures and colors.

We plan to continue with implementation and issue review next week.


5. *Issues Inventory*.  Mantis review, have we tagged all relevant issues as #X3Dv4 ?

	Mantis Issue Tracker


6. Teleconference update

We have switched to Zoom channel, to good effect.  It allows use of internet audio, screen sharing and chat with links.

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Members and invited experts are welcome.  We are an open organization. Please let us know if you have an important topic to present or discuss.

The X3D Graphics Working Group addresses all X3D specification issues and coordinates the technical development of future improvements.

Each week we report out both public and member-only information - membership has value.  To become a Web3D Consortium member:
	Join the Web3D Consortium


No member-only information was relayed in these minutes.

*Ten weeks to go before our X3Dv4 contributions deadline*

	X3D Version 4

We will continue reviewing individual issues and implementation status next week (sections 4 and 5 above).

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 http://faculty.nps.edu/brutzman
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