[x3d-public] X3D V4 Draft Requirements Proposal

Andreas Plesch andreasplesch at gmail.com
Mon Mar 27 20:05:33 PDT 2017 

Hi Leonard,

this is a good, demanding list. Some quick comments below.

From: Leonard Daly <Leonard.Daly at realism.com>
To: X3D Public <x3d-public at web3d.org>
Subject: [x3d-public] X3D V4 Draft Requirements Proposal

Last week there was a bit of conversation on the 3D WG list about
requirements. I am sending my contribution on the topic of X3D V4
requirements to the public list to get increased conversation. Note that
this is NOT the product of the WG and I am not claiming that these are
final. This is only a personal early draft of requirements for X3D
running in a web browser environment. Please feel free to discuss or
propose additions/changes to this list.


*Requirements*
Boundary conditions: This is just for X3D running in a web browser and
integrated with HTML. If there is X3D outside of this limitation, these
requirements may or may not apply.

Note: Some of these requirements may overlap by varying amounts. It was
easier to specify them this way then trying to make a complete and
non-overlapping set. I'm not going to even claim that this is a complete
set, but it is a beginning.

For those that want XHTML, then convert all references to HTML to XHTML
and make the appropriate syntax changes. The differences between HTML
and XHTML in the appearance of the elements and attributes is that XHTML
is strict. This amounts to closing elements, elements and attributes are
lower case, mandatory elements and attributes, different MIME type
(text/html vs. application/xml or applications/xhtml+xml), and quoted
attributes -- see https://www.w3schools.com/html/html_xhtml.asp for
details. The WhatWG has a pretty good documentation page on the
differences at https://wiki.whatwg.org/wiki/HTML_vs._XHTML.


1) Look "like" HTML (5).
   a) Elements (nodes in X3D-speak) shall be case independent
   b) Attributes (fields in X3D-speak) shall be case independent
   c) X3D nodes shall not have name conflicts with any HTML-defined elements


I believe the HTML5 Custom Elements spec requires a prefix-name format for
element names. While allowing lowercase should we also allow
'x3d-transform' format alternative names ?


   d) All X3D nodes shall support all HTML Global Attributes
(https://www.w3schools.com/tags/ref_standardattributes.asp)


Is this equivalent to requiring that X3D nodes need to derive from
HTMLElement as defined in the DOM ?

   e) All X3D fields with the same name as HTML attributes shall behave
as the HTML element
   f) TBD: Not all style attributes apply to X3D nodes & fields

2) Function "like" HTML (5).
   a) All nodes shall be fully integrated with the DOM [This may need to
change if certain nodes need to remain hidden from the DOM. For example,
the manner which X3DOM implements Inline.]
   b) The scene graph does not need to be DOM (or a portion of it).


Not sure I can follow here.

   c) Changes to the DOM shall be reflected in the scene graph
   d) Changes to the scene graph shall be reflected in the DOM


Using the DOM to maintain and reflect state is often considered slow. Could
d) be optional ? Changes to the scene graph cause events which can be
listened to if required. (This is why cobweb-dom does not reflect back
interpolator output to the DOM at this point).

   e) Events are handled as HTML events
   f) DOM is the external (i.e., from the web page) API to the scene graph


X3dom does it that way. One could add that this external API could be
implemented using the SAI thereby guaranteeing X3D event flow determinism.


3) X3D shall support the evolving web standards for flat-3D (WebGL), VR
(WebVR) and AR (nothing yet).


I still want to complete my diff between webvr draft standard and x3d.
However, it looks like the webvr standard already evolved quite a bit.


4) Existing features & functionality
   a) Perform the following tasks with the requirements that is be
conflict with the above
     i) Conduct a review of all existing features (nodes) to determine
if any should be deprecated in V4
     ii) Conduct a review of all existing functionality (run-time) to
determine if any should be deprecated or changed in V4
   b) Include all features and functionality that passes the above reviews

5) Additional features shall be added
   a) Deformable-skin joint based animation
   b) Support for multiple geometry formats, including OBJ, glTF


I have a pretty good idea about gltf2 support in x3dom, see my x3dom GitHub
issue. But since it is quite a bit of work, it will be some time/use case.

   c) Increased Material support with a standard library of pre-defined
shaders


Three.js has good shaders including for PBR. But again quite a bit of work.
Not sure if Fraunhofer is that engaged since there may be commercialization
interest.

   d) Mechanism to navigate a scene without a pointing device
   e) Mechanism to touch or select objects without a pointing device


Or with wand or controller.

   f) Review other 3D/VR display technologies (XML3D, A-Frame, GLAM,
etc.) to determine if there are features that should be included


The three.js examples are also inspiring. Postprocessing of the rendered
frame in another shader stage comes to mind.  There are probably many more
modern graphics methods which need some support. Ambient occlusion ssao ?
Motion blur ? Distance defocus ?

Generally, the vrml spec. was written before the advent of powerful GPUs
(massively parallel super computers) where it now can be faster to repeat
the same fragment shader operation for each pixel (perhaps a million times)
rather than update data between cpu and gpu once. Not sure what the
consequences exactly are other than being shader friendly in some way.


Andreas



--
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Chair
President, Daly Realism - /Creating the Future/
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