[x3d-public] X3D Working Group agenda: endgame review: TextureProjector nodes, do we include shadows?

[Don Brutzman]

Thanks to everyone active for all work on review, implementation and evaluation as we finalize X3D4 for release this year.

Dialog always helps. Am happy to note that we are in the endgame for X3D4 technical improvements.

If cc:ed X3D4 implementers cannot attend, respectfully request that you provide responses (public or private) beforehand if possible.

Below please find agenda for this week's X3D Working Group meeting, Friday 16 October, 08-0930 pacific time.

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Participation:

[0.1] Web3D Teleconference Information
        https://www.web3d.org/member/teleconference-information

> Please use the following link for all Web3D Consortium Meetings.
>
> Join URL: https://us02web.zoom.us/j/81634670698?pwd=a1VPeU5tN01rc21Oa3hScUlHK0Rxdz09

Last week's minutes and followups:

[0.2] [x3d-public] X3D Working Group agenda 9 OCT 2020: game plan and trajectory for voting on release of X3D4 specification
       http://web3d.org/pipermail/x3d-public_web3d.org/2020-October/013764.html

[0.3] [x3d-public] comments on Projective texture mapping: near/far naming, textureTransform
       http://web3d.org/pipermail/x3d-public_web3d.org/2020-October/013780.html

[0.4] [x3d-public] X3D working group meeting Friday on TextureProjector nodes: special light or texture-mapping technique?
       http://web3d.org/pipermail/x3d-public_web3d.org/2020-October/013784.html

[0.5] [x3d-public] announce: X3D4 updates
       http://web3d.org/pipermail/x3d-public_web3d.org/2020-October/013791.html

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1. Outreach

a. Web3D 2020 Conference registration is FREE and open, schedule released online.  Over 100 people have registered and all papers/posters are now submitted to ACM Digital Library.  They will be freely available for 1 month when the conference starts.

[1.0] Web3D 2020 Conference registration
       https://web3d.siggraph.org

[1.1] ACM Digital Library: Web3D Conference
       https://dl.acm.org/conference/web3d

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b. Anita has been working on establishing an excellent new blog.

[1.2] blog entry "X3D in a Box"
       https://webx3d.org/box-of-x3d

It has seemed somewhat difficult to get a transparent background as part of the X3D model floating over the web page.  Surprisingly, we haven't found a lot of people doing this yet.  We will look at the latest/greatest and focus on background transparency.

[1.3] X3D Tooltips: Background transparency
       https://www.web3d.org/x3d/tooltips/X3dTooltips.html#Background.transparency

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2. Projective Texture Mapping (PTM)

[2.0] X3D4 Working Draft 2, 42  Projective Texture Mapping (PTM) Component
       https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD2/Part01/components/ProjectiveTextureMapping.html

a. Critical point of difference: do the TextureProjectorParallel/TextureProjectorPerspective nodes implement X3DLightNode, or are they simply a texture-wrapping function for geometry?

b. Include textureTransform?  This addition seems simple, logical and consistent.

c. Component naming concern: if we indeed take an X3DLightNode approach, then "Projective Texture Mapping (PTM)" component seems misleading because we are not mapping any texture to any geometry per se.  "TextureProjector*" names are OK.  So, might a better name be "Texture Projector" component?  Seems clearer and more consistent.

d. Conceptual naming concern: is TextureProjectorParallel more appropriately named/designed as orthographic?  Fine point perhaps.

e. Node naming consistency: typically we keep common part of node names last (e.g. Background/TextureBackground nodes, *Material nodes, others).

Perhaps these are better names:

- PerspectiveTextureProjector (or simply TextureProjector)
- ParallelTextureProjector or OrthoTextureProjector

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3. Shadows - or not?

Lots of excellent discussion and prior review.  Time to decide.

[3.0] [x3d-public] X3D minutes 2 OCT 2020: draft X3D4 Shape component, 3 approaches to X3D4 shadows, RenderingEnvironment node, audio concepts
       http://web3d.org/pipermail/x3d-public_web3d.org/2020-October/013726.html

a. Do we have a field on X3DLightNode indicating that a light node can cast shadows?

b. Is the best field X3DLightNode shadowIntensity?  Default value is 0.0 (for backwards compatibility of X3D content).  Is that sufficient to omit a boolean?

c. Do we also provide a boolean field on Shape nodes indicating they can cast shadows?  If so, then is default on or off?

d. Specification prose?

Upside: minimalist changes like the above for X3D content enables the creation of scene content that lets authors take advantage of shadows, while X3D browsers can continue to innovate regarding what algorithms they use.

Downside: much-requested feature remains unfinished, and specialty shadow implementations remain non-interoperable.

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4. Color interpolation of Background nodes

[4.1] [x3d-public] Which color space for Background color interpolation
       http://web3d.org/pipermail/x3d-public_web3d.org/2020-October/013778.html

Implementation discussion on email thread apparently indicates that X3D4 specification improvement is needed:

> > So perhaps it is not too late to add "in RGB color space" to
> >
> > https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/enveffects.html#Backgrounds

Updated reference:

[4.2] X3D4 WD2 24 Environmental effects component
       24.2.1 Backgrounds
       https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD2/Part01/components/environmentalEffects.html#Backgrounds

Paragraphs 4 and 5 each conclude with
- "The sky colour is linearly interpolated between the specified skyColor values."
- "The ground colour is linearly interpolated between the specified groundColor values."

So... is that addition "in RGB color space" (appended at the end of each sentence) sufficient for X3D4 specification prose ?

Or should we allow some variation by browsers and instead append ", typically in RGB color space" ?

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Appreciate all consideration of these resolvable issues.

It will be good to finish everyone's "wish list" and get to the new era of tuning and polishing X3D4 models & player implementations.

Tick tock tick tock tick tock...  Have fun with X3D4!  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 http://faculty.nps.edu/brutzman