[x3d-public] X3D Working Group meeting 23 SEP 2022: Mantis issues review, SvgTexture

Thu Sep 29 06:04:15 PDT 2022

We cannot represent 100% of glTF 2.0 features as X3D nodes. We're not
there (yet).

So the statement “X3D 4.0 provides full support for inline loading or
directly representing glTF 2.0 models.” sounds too strong IMHO. At
least for me, the words "full" and "directly representing" above would
suggest that we can express 100% glTF features in X3D, which we can't.

We achieved progress in X3D 4.0 (we have PBR which is compatible with
glTF). But we still have various missing things:

1. Compressed geometry from glTF -- it can loaded, but it has to
become decompressed in the process. (like CGE) Or the browser has to
load glTF meshes without converting them to X3D meshes. (like FreeWRL)
Or browser has to use browser-specific extensions (like X3DOM).

    We don't yet have the "ideal solution" - X3D nodes for mesh data
that can be uploaded to GPU directly. Document
https://www.web3d.org/specifications/FeaturesComparisonX3D4glTF2.pdf
also states it --- we added together on one call valid statement "X3D
native nodes directly corresponding to glTF compressed geometry not
supported, but Inline loading of glb models is supported."

2. Various other things I mentioned in
https://github.com/michaliskambi/x3d-tests/wiki/Converting-glTF-to-X3D
. Some have extensions in CGE, for some -- we don't yet have a ready
solution:

2.1. Tangent node (extension in CGE ,
https://castle-engine.io/x3d_implementation_rendering_extensions.php#section_Explicit_tangent_vectors
)

2.2. Modulate mode for Color/ColorRGBA (
https://github.com/michaliskambi/x3d-tests/wiki/Converting-glTF-to-X3D#per-vertex-colors
, https://castle-engine.io/x3d_implementation_rendering_extensions.php#section_ext_color_mode
)

2.3. glTF CubicSpline and Step interpolation. CubicSpline can be
approximated in X3D by converting to Linear with more points (e.g.
10x), Step can be performed by converting to Linear with 2x points
(CGE has extension to do "Step" explicitly). But that's not perfect.

2.4. Skinned mesh animation. We all agreed that glTF skinned mesh
animation can be probably expressed as X3D H-Anim nodes, but so far
nobody (from what I know) actually figured out how to do this
conversion (not to mention -- conversion that preserves the
efficiency, and allows to play glTF skinned animation on GPU without
calculating anything extra on browser). CGE is just playing glTF
skinned mesh animation without the help of H-Anim nodes. Last I heard,
Andreas was working on it in X3DOM, but wrote it is unfinished.

Regards,
Michalis

czw., 29 wrz 2022 o 13:00 Brutzman, Donald (Don) (CIV)
<brutzman at nps.edu> napisał(a):

>
> I added a summary statement (quoted below) and made a few formatting improvements.
>
>
>
> Features Comparison X3D4 glTF2 (.pdf) spreadsheet shows complete interoperability with glTF rendering.
> https://www.web3d.org/specifications/FeaturesComparisonX3D4glTF2.pdf
> https://www.web3d.org/specifications/FeaturesComparisonX3D4glTF2.xlsx
> “X3D 4.0 provides full support for inline loading or directly representing glTF 2.0 models.”
>
>
>
> As ever, all review comments and questions welcome.  Have fun with X3D!  8)
>
>
>
> 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: Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
> Sent: Saturday, September 24, 2022 7:55 AM
> To: John Carlson <yottzumm at gmail.com>
> Cc: X3D Public Mailing List (x3d-public at web3d.org) <x3d-public at web3d.org>; Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
> Subject: RE: [x3d-public] X3D Working Group meeting 23 SEP 2022: Mantis issues review, SvgTexture
>
>
>
> John, there is a bit more in the issue and the references.
>
>
>
> SVG produces animatable interactive 2D images through vector graphics.  So it has characteristics of both ImageTexture and MovieTexture (and interpolators and scriptable event models).
>
>
>
> Dick’s point yesterday was that implementing such a combination is different and bigger than ImageTexture or MovieTexture.  The ways that an author might use an SVG model are similar, but when you think of how a browser might do it and then add computation, user interaction, security, etc. etc. then the design perspective is quite different.  This leads us to the tried-and-true approach of implementing and testing further, most likely as a new node.
>
>
>
> So I think that is an interesting and important justification that he made.  We offer it back to the group for review and discussion – thanks for your points.
>
>
>
> 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: John Carlson <yottzumm at gmail.com>
> Sent: Friday, September 23, 2022 5:33 PM
> To: Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
> Cc: X3D Public Mailing List (x3d-public at web3d.org) <x3d-public at web3d.org>
> Subject: Re: [x3d-public] X3D Working Group meeting 23 SEP 2022: Mantis issues review, ballot deadlines, X3D Application Stack Layer Examples diagram
>
>
>
> Recommendation:  SvgTexture should be a single frame MovieTexture for now, with possible extensions to animation with ROUTEs and ECMAscript, if animation is enabled on SvgTexture node.  I don’t know if MovieTexture enables/disables animation, but my guess is, yes.
>
>
>
> Disabling/enabling animation of SVGs should be in more inclusive profiles.
>
>
>
> Is that simple enough?
>
>
>
> On Fri, Sep 23, 2022 at 7:23 PM John Carlson <yottzumm at gmail.com> wrote:
>
> Consider:   SVG is a manipulation language for inserting 2D graphics into a scene.   Definition languages are more closely related to schemas, or possibly for manipulating schema.  After insertion into a scene, ECMAscript is typically used for manipulation.   ROUTEs should be allowed to as well.
>
> SVGs should be considered animations with popular packages being D3.js.
>
>
>
> Otherwise,  SVG is a declarative language, similar to X3D and HTML.   Last I heard, there was no official schema for SVG.
>
>
>
> If the SVG is animated by ECMAscript, wouldn’t it more properly be used to texture surfaces and volumes with a MovieTexture?  Are MovieTextures 2D or 3D?   What textures are used for VolumeRendering?
>
>
>
> On Fri, Sep 23, 2022 at 1:44 PM Brutzman, Donald (Don) (CIV) <brutzman at nps.edu> wrote:
>
> 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.
>
>
>
> 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
> * "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.
>
>
>
>
>
> 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.
>
>
>
>
>
> 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/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
>
>
>
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