[x3d-public] X3D meeting agenda 18 FEB 2022: SpotLight angles, Volume Rendering component

[Michalis Kamburelis]

Thanks, I'll join this Friday!

As for goals, my quick answers to SpotLight issues:

> is figure OK?

Yes.

> Is relationship correct, typically beamWidth <= cutoffAngle.

Depends on how you define "typically". Both beamWidth <= cutoffAngle.
and beamWidth > cutoffAngle make sense, they make sense for authors
(and real-world) and existing SpotLight prose and equations explicitly
make both situations sensible. Use beamWidth < cutoffAngle if you want
smooth spot edges, use beamWidth >= cutoffAngle if you want sharp spot
edges -- both make sense.

> Should we modify default values?

Yes.

The current defaults (in X3D 3.3 and 4.0) are weird IMHO (cutOffAngle
= pi / 2 is too large, no other software has so large default).

The defaults in VRML 97, X3D 3.0, 3.1 and 3.2  were better.
cutOffAngle = pi / 4 makes most sense. And is consistent with
outerConeAngle in glTF.

So we have a choice:

A. keep the new X3D 3.3 / 4.0 defaults (that are IMHO bad)

B. revert to defaults in VRML 97, X3D 3.0, 3.1 and 3.2 (best option
IMHO, and likely matches already what X3D browsers are doing -- does
anyone have report which browsers actually adjusted to X3D 3.3
defaults?)

C. invent completely new defaults. Like cutOffAngle = pi / 4 and
beamWidth = pi / 8 or 0.

Note that existing software/formats have various defaults in general
for this (see my mail in thread
https://web3d.org/pipermail/x3d-public_web3d.org/2022-February/016744.html
where I list glTF, Blender, Unity), and even slightly different way of
smoothing. So I don't see much benefit in doing C. I think B is the
simplest and correct resolution :)

> Should we improve prose for clarity?

No, the prose is good. Both prose and equation are good, prose even
explicitly says beamWidth may be > cutOffAngle in which case there's a
sharp edge to spot.

Looking at Mantis ticket
https://www.web3d.org/member-only/mantis/view.php?id=441

- Someone made wrong assumption "Thus default values need to have
cutOffAngle > beamWidth." . Why? They don't need to. We had
cutOffAngle = pi/4 and beamWidth=pi/2 for a long time, implemented by
many VRML/X3D browsers, this was actually good.

- Then someone made wrong action to fix it, exchanging cutOffAngle and
beamWidth defaults. Even if you really want cutOffAngle > beamWidth as
default, then you should have decreased beamWidth, but not change
cutOffAngle IMHO.

> Nicholas and Michalis: please comment on following issues:

Sorry, I admit I didn't have time to look at Volume Rendering component yet.

Regards,
Michalis


śr., 16 lut 2022 o 05:53 Brutzman, Donald (Don) (CIV)
<brutzman at nps.edu> napisał(a):
>
> Regular Friday meeting 08-0900 Friday, call information below.
>
>
>
> Videoconference Connectivity:
>
> https://us02web.zoom.us/j/81634670698?pwd=a1VPeU5tN01rc21Oa3hScUlHK0Rxdz09
> https://zoom.us/j/148206572  Password 483805
> https://www.web3d.org/member/teleconference-information
>
>
>
> Spiraling questions about SpotLight field relationships and default values, beamwidth and cutoffAngle
>
>
>
> X3D4 Architecture, Lighting component, clause 17.4.4 SpotLight
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD1/Part01/components/lighting.html#SpotLight
>
>
>
> excerpted
>
>
>
> SpotLight : X3DLightNode {
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>
>
>   SFFloat [in,out] beamWidth        π/4      (0,π/2]
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>
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>   SFFloat [in,out] cutOffAngle      π/2      (0,π/2]
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> }
>
>
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> X3D4 Architecture, Lighting component, Figure 17.1 — SpotLight node
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD1/Part01/components/lighting.html#f-SpotLightnode
>
>
>
> [x3d-public] Defaults of SpotLight.cutOffAngle, beamWidth changed (maybe by mistake) in X3D 3.3
> https://web3d.org/pipermail/x3d-public_web3d.org/2022-February/016744.html
>
>
>
> Mantis 441: 17.4.3 SpotLight -- Default Values (resolved 2009)
> https://www.web3d.org/member-only/mantis/view.php?id=441
>
>
>
> Michalis has agreed to walk us through this.  Goal outcomes for confirmation:
>
> is figure OK?
> Is relationship correct, typically beamWidth <= cutoffAngle
> Should we modify default values?
> Should we improve prose for clarity?
>
>
>
> = = =
>
> Working on Mantis issues for Volume Rendering component
>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD1/Part01/Architecture.html
>
>
>
> X3D4 Architecture, Volume rendering component
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD1/Part01/Architecture.html
>
>
>
> Nicholas and Michalis: please comment on following issues:
>
>
>
> Mantis 917: Table 41.7 Volume rendering component support levels - ShadedVolumeStyle shadows support unclear
> https://www.web3d.org/member-only/mantis/view.php?id=917
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>
>
> and
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> Mantis 709: 41.4.4 ComposedVolumeStyle - Remove reference to ordered field
> https://www.web3d.org/member-only/mantis/view.php?id=709
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>
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> Can we remove ‘ordered’ field from table?
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>
>
> = = =
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>
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> Other topics of group interest… are always welcome.
>
>
> Membership has value! Please consider joining Web3D Consortium.
>
> https://www.web3D.org/join
>
>
>
> Thanks for all preparations and inputs.  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
>
>