[x3d-public] X3D minutes 4 DEC 2020: resolving X3D4 endgame issues
John Carlson
yottzumm at gmail.com
Sat Dec 5 14:48:40 PST 2020
+1 for Michalis!
I believe that higher intensities can be achieved through cubemaps but I
have little evidence besides my examples, which I am not sure if they do
HDR or not.
The goal is to achieve realistic lighting.
Thanks
John
On Sat, Dec 5, 2020 at 4:15 PM Michalis Kamburelis <michalis.kambi at gmail.com>
wrote:
> Don,
>
> Your arguments about the light intensity limit at 1.0 come down to
> "this limit seemed to work for us" :) And I see your point, because it
> *seemed* like it was a working solution. Although I will now argue
> that it was never a working solution :)
>
> The thing is, it was not really working (even with the Phong lighting
> model), if you try to create lights that reflect the reality, i.e.
> have a realistic falloff. The exact equations for "realistic falloff"
> in glTF are in
> https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
> , but within the X3D they can approximated simply by using
> "attenuation = 0 0 1". Simplifying, this means that you have an
> inverse-quadratic-with-distance falloff, that is you multiply light
> contribution at each point by
>
> 1 / lightDistance^2
>
> Now, if you try to use such realistic falloff, you will see that
> intensity = 1.0 can only result in very very dim lights, i.e. these
> lights influence quickly goes to practical zero . You will not be able
> to express realistic lighting conditions at all.
>
> This is why I argue for removing this limit. It's not only about the
> physical lighting model, it applies to both Phong (Material) and
> physical (PhysicalMaterial) models. It's not about glTF consistency or
> Blender -- any description of physically-correct lights will allow for
> larger intensity values. Any authoring tool nowadays will also allow
> you to have lights with intensity > 1, if it supports realistic
> lighting.
>
> So it's not a theoretical discussion, the limit at 1.0 is actually,
> practically, a problem :)
>
> Hope this makes it clearer. The way to test it is just to create a
> dummy scene in Blender, add light sources, export to glTF and try to
> open e.g. in view3dscene -- you will immediately see that limiting
> yourself to "intensity = 1.0" is just limiting too much, you cannot
> create correctly bright scenes. Of course you could create a lot of
> light sources to simulate "one very bright light source", but then it
> comes at very large efficiency cost (each light source takes time to
> computer), for no good reason (as I bet that, for any practical
> renderer implementation, removing the 1.0 limit is almost no work).
>
> I just checked Unity, and they also allow larger intensity (
> https://docs.unity3d.com/ScriptReference/Light-intensity.html ),
> although they chose to limit it at 8.0. (Which is also an arbitrary
> limit, with no relation to reality -- I don't know why they chose
> "8.0", I assume it just made it easier to show in the editor as a
> range.)
>
> Regards,
> Michalis
>
> sob., 5 gru 2020 o 18:48 Don Brutzman <brutzman at nps.edu> napisał(a):
> >
> > Hi Michalis.
> >
> > For X3DLightNode /intensity/ field, the wording about "nominal lighting
> intensity" is trying to express "regular practice for light intensity" i.e.
> our usual authoring expectations, which remain unchanged.
> >
> > The point is that composability of X3D scenes has always assumed
> consistent use of lights. This is not a mathematical issue.
> >
> > If everyone uses light intensity [0,1] as we have for oh-so-many years,
> things seem to work satisfactorily when X3D models and scenes are composed
> together.
> >
> > Potential problems:
> >
> > a. If someone decides "hey my models are very important so my lights
> will have intensity of 1000" then that has bad impact when loaded with
> other scenes.
> >
> > b. When someone's exporter/editor drops a decimal point on light
> intensity, it goes undetected by preprocessor validation and unflagged at
> run time, with the same bad impact when loaded with other scenes.
> >
> > c. When some other tool performs a "save as X3D" operation, they have no
> indication that their custom light conventions might need adjustment.
> >
> > d. Presumably if someone loads a glTF model with really bright lights,
> the same composition problems occur due to mismatched lighting schemes.
> >
> > Quality thus suffers from inconsistent practice, and such a lack of
> lighting regularity might significantly degrade X3D model re-use overall.
> >
> > Meanwhile, it has been noted in the working group teleconferences that
> current X3D specification already allows definitions of higher intensity
> for special effects, for example by putting multiple coincident PointLight
> nodes at the same location.
> >
> > Further, if there has been a use case that makes extra-high-intensity
> lights of practical value, it hasn't been communicated or shared yet.
> Please advise if you have one.
> >
> > Personally I think it is a bad idea to change this limit, might agree if
> the words can strongly express regular practice so that norms remain
> understood.
> >
> > BTW, my nomination as first law of engineering: "if it ain't broke,
> don't fix it." We have 23 years of successful practice preceding this
> recent proposed change.
> >
> > Perhaps better words that the initial attempt below can express this
> expectation for composition.
> >
> > ... Or perhaps "discretion is the better part of valor" and we should
> not let our mathematical creativity jeopardize what is already working
> well, i.e. /intensity/ range [0,1] as ever.
> >
> > Absent a use case other than "gee whiz granddad, everybody else can do
> it" - this change is not yet sufficiently justified for inclusion in X3D4.
> >
> > Thanks for continuing to share your opinions on this important matter.
> >
> >
> > On 12/4/2020 12:59 PM, Michalis Kamburelis wrote:
> > >
> > >
> > > As for the "phrasing of intensity values > 1": I admit I don't
> > > understand what this text is trying to say.
> > >
> > > - "Nominal lighting intensity and ambientIntensity values are
> > > typically limited to a range [0,1] for consistent composability of
> > > scenes."
> > >
> > > - "Consider maintaining nominal upper limit 1"
> > >
> > > What is a "nominal lighting intensity"? What is a "nominal upper
> limit"?
> >
> > rationale above.
> >
> > > The text is contradictory, basically claiming that values > 1.0 is
> > > absolutely OK, but at the same time suggesting to have them <= 1.0.
> >
> > No worries, in the minutes you are looking at meeting notes for a
> possible draft revision... Sorry if there was an omission or error. We
> are trying to make an informed decision, so rest assured that final prose
> will match final specified bounds in X3D4 specification, validation tools,
> X3DUOM, tooltips, test cases, etc.
> >
> > > As I explained in an earlier thread, I fail to see the reason to treat
> > > values of intensity > 1.0 in any way special. They go through the same
> > > equations. Browsers practically do not have to do anything to support
> > > them. The values > 1.0 also do not cause any additional problems
> > > (because final colors could be > 1.0 anyway, even in X3D 3). According
> > > to physical interpretation (given in the Lighting component, for
> > > physical lighting model) there's also no reason to limit them to 1.0,
> > > so authoring tools should not limit them either (Blender doesn't have
> > > any limit on light power).
> >
> > rationale above.
> >
> > of note is that our use cases for any arbitrary sharable model on Web
> are broader than Blender, which provides an excellent authoring environment
> for authors deliberately putting their models together.
> >
> > > Note that there's no reason to mix this with ambientIntensity. This
> > > one can stay, as in X3D 3, limited to [0,1]. It has no correct
> > > physical interpretation anyway, it's just a multiplier for material's
> > > ambient.
> >
> > Very good. Thanks for feedback that X3DLightNode /ambientIntensity/
> field can remain with [0,1] constraints, we weren't sure about that on the
> past two conference calls. Agreed, no change.
> >
> > > Regards,
> > > Michalis
> >
> > p.s. am happy to discuss if that helps, please feel free to call. we
> need to lock this down by next Friday.
> >
> > > pt., 4 gru 2020 o 19:42 Don Brutzman <brutzman at nps.edu> napisał(a):
> > >>
> > >> Attendees: Vince Marchetti, Dick Puk, Don Brutzman
> > >>
> > >> Big agenda but milestone deadline is looming and all issues are
> familiar. Thanks for all advance meeting preparation, we hope to proceed
> rapidly.
> > >>
> > >> We now meet one hour later than before: 09-1000 Pacific time.
> > >>
> > >> [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
> > >>
> > >> Prior minutes:
> > >>
> > >> [0.2] [x3d-public] X3D working group minutes: scheduling, conference
> quicklook, specification work planning, X3D4 finalization
> > >>
> https://web3d.org/pipermail/x3d-public_web3d.org/2020-November/014002.html
> > >>
> > >> ---
> > >>
> > >> 1. X3D4 topics
> > >>
> > >> [1.0] X3D4
> > >> https://www.web3D.org/x3d4
> > >>
> > >> Changes to X3D4 specification on members-only github are also being
> refreshed daily at
> > >>
> > >> [1.1] X3D4 Working Draft 3
> > >>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD3/
> > >>
> > >> Corresponding pristine text in preparation for Web3D Consortium
> member ballot is currently being autogenerated along with a log of both
> corrections and remaining issues.
> > >>
> > >> ---
> > >>
> > >> a. MIDI 2.0 and Web Midi accepted. Audio and sound changes complete,
> checked in.
> > >>
> > >> [2] [x3d-public] X3D4 Sound Component and MIDI 2.0 review: accepted
> for ballot
> > >>
> https://web3d.org/pipermail/x3d-public_web3d.org/2020-December/014188.html
> > >>
> > >> Many thanks for many reviews and multiple endorsements.
> > >>
> > >> ---
> > >>
> > >> b. Continued review and editing of prose for clarity in Lighting and
> Shape components, with focus on glTF support.
> > >>
> > >> [3] Various comments reading X3Dv4 current working draft (WD3 in
> GitHub repository)
> > >>
> https://web3d.org/pipermail/x3d-public_web3d.org/2020-December/014189.html
> > >>
> > >> No problems noted but more editing work needed. Michalis has the
> baton for some technical clarifications, then Dick and Don will continue
> working on prose phrasing to meet ISO editorial conventions.
> > >>
> > >> *** TODO
> > >>
> > >> Note phrasing of intensity values > 1:
> > >> =====================
> > >>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD3/Part01/components/lighting.html
> > >>
> > >> 17.3.1 X3DLightNode
> > >> X3DLightNode : X3DChildNode {
> > >>
> > >> SFFloat [in,out] ambientIntensity 1 [0,1]
> > >> or
> > >> SFFloat [in,out] ambientIntensity 1 [0,∞] # Consider
> maintaining nominal upper limit 1
> > >>
> > >> SFFloat [in,out] intensity 1 [0,1]
> > >> or
> > >> SFFloat [in,out] intensity 1 [0,∞] # Consider
> maintaining nominal upper limit 1
> > >>
> > >> SFColor [in,out] color 1 1 1 [0,1]
> > >> SFBool [in,out] global FALSE
> > >>
> > >> Nominal lighting intensity and ambientIntensity values are typically
> limited to a range [0,1] for consistent composability of scenes. If
> multiple light sources illuminate a single geometric shape, the totals for
> color values computed at a given point may be greater than one. Using
> intensity values greater than one can provide useful effects and is allowed
> without error.
> > >> =====================
> > >>
> > >> ---
> > >>
> > >> c. Gamma correction
> > >>
> > >> Of note in this long-running issue:
> > >> - no single entity (hardware, software, browser, author) can yet
> drive to a cross-platform solution.
> > >> - stating accepted expectation (gamma correction is expected) might
> lead to false sense of optimism.
> > >> - still complex but some further progress might be expected with XR
> activity next year.
> > >>
> > >> and realization that there is something we can mostly control:
> rendering screen to image, allowing visual checking/comparison and also
> unit testing. No requirement that all browsers look exactly the same -
> rendering pipelines have some leeway - but at least we can test compare and
> keep improving. Especially useful with addition of physically based and
> non-photorealistic (unlit) rendering.
> > >>
> > >> [4] [x3d-public] [...] Gamma Correction for X3D4 final draft
> > >>
> https://web3d.org/pipermail/x3d-public_web3d.org/2020-November/014103.html
> > >>
> > >> summarized as
> > >>
> > >>> There are 2 spec choices below: acknowledging norms by simply
> stating that gamma correction is typically expected,
> > >>> or else continuing to say nothing.
> > >>
> > >> Check consensus: adding no additional statement still seems most
> pragmatic? So "not" say we all...
> > >>
> > >> ---
> > >>
> > >> d. Putting default duration bounds on url refresh activity
> > >>
> > >> Clearly we don't want a lot of unclosed 3D scenes and window frames
> becoming zombie network loads (or even Denial Of Service DOS threats).
> > >>
> > >> [5] [x3d-public] X3D4 security-related field addition: X3DUrlObject
> refreshTimeLimit
> > >>
> http://web3d.org/pipermail/x3d-public_web3d.org/2020-November/014182.html
> > >>
> > >> with John Carlson's follow-on reply exploring rationale and examples
> further.
> > >>
> > >> Recommendation: include this field (X3DUrlObject refreshTimeLimit) as
> a prudent security precaution.
> > >>
> > >> ========================
> > >> 9.3.2 X3DUrlObject
> > >>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD3/Part01/components/networking.html#X3DUrlObject
> > >>
> > >> X3DUrlObject {
> > >> SFString [in,out] description ""
> > >> SFBool [in,out] load TRUE
> > >> SFTime [in,out] refresh 0.0 [0,∞)
> > >> MFString [in,out] url [] [URI]
> > >> }
> > >> [...]
> > >> =====================
> > >>
> > >> Proposed field for maximum refresh duration. Note this is not the
> same as browser working its way through url list, and finding or timing out
> on any individual url, which is owned by the software implementation and
> the associated network protocol.
> > >>
> > >> SFTime [in,out] refreshTimeLimit 3600.0 [0,infinity]
> > >>
> > >> "The refreshTimeLimit field defines the maximum duration in seconds
> that /refresh/ activity is allowed to occur. This field is intended to
> reduce potential risks associated with indefinite repetition of automatic
> link retrieval. Setting the /load/ field to TRUE resets the
> refreshTimeLimit clock. If refreshTimeLimit is exceeded then load is set to
> FALSE."
> > >>
> > >> Alternate names might be autoRefreshTimeLimit, together with renaming
> /refresh/ as /autoRefresh/.
> > >>
> > >> X3DUrlObject {
> > >> SFString [in,out] description ""
> > >> SFBool [in,out] load TRUE
> > >> SFTime [in,out] autoRefresh 0.0 [0,∞)
> > >> SFTime [in,out] autoRefreshTimeLimit 3600.0 [0,infinity]
> > >> MFString [in,out] url [] [URI]
> > >> }
> > >> [...]
> > >>
> > >> Absent further comment, we expect to proceed with this clarifying
> naming refinement.
> > >>
> > >> ---
> > >>
> > >> e. References review requested
> > >>
> > >> [6.0] [x3d-public] X3D4 endgame review: normative references and
> informative bibliography
> > >> http:s//
> web3d.org/pipermail/x3d-public_web3d.org/2020-November/014122.html
> > >>
> > >> Note several replies that are not part of the thread per se.
> > >>
> > >> [6.1] X3D4 Architecture, Normative references
> > >>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD3/Part01/references.html
> > >>
> > >> [6.2] X3D4 Architecture, (Informative) bibliography
> > >>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD3/Part01/bibliography.html
> > >>
> > >> Continuing review welcome, thanks for several improvements received.
> > >>
> > >> ---
> > >>
> > >> f. ExternalShape, ExternalGeometry?
> > >>
> > >> ExternalShape handled by Inline.
> > >>
> > >> [7.0] X3D4 9.4.2 Inline
> > >>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD3/Part01/components/networking.html#Inline
> > >>
> > >> What about ExternalGeometry for glTF models, is it needed? Not
> finding it in Mantis, wondering if there is no strong use case or maybe
> we've dropped a ball. Wondering if this was an intentional omission or
> overlooked?
> > >>
> > >> Presumed use case: glTF file contains a mesh (perhaps a compressed
> mesh) and then X3D Appearance gets applied.
> > >>
> > >> Can we add this node? If overlooked then it would have to be
> non-controversial and already have multiple implementations, at this late
> date...
> > >>
> > >> As of today it seems too late for X3D4, feedback welcome.
> > >>
> > >> ---
> > >>
> > >> g. Event Utility node clarifications
> > >>
> > >> Thanks Andreas for remembering this long-overlooked issue.
> > >>
> > >> [8.0] [x3d-public] X3D4 draft nearing readiness for ballot; Mantis
> 519 Event utilities, ignoring set_boolean false events
> > >>
> https://web3d.org/pipermail/x3d-public_web3d.org/2020-November/014185.html
> > >>
> > >> This applies to IntegerTrigger and TimeTrigger nodes, ignoring
> set_boolean FALSE improves logical understanding and simplifies event
> animation chains.
> > >>
> > >> Absent objections (none heard) will apply this straightforward
> change. No problems with prior compatibility identified as a result of
> this logical refinement.
> > >>
> > >> Review led Dick and I to also look at related issue
> > >>
> > >> [8.1] Mantis 1183, 30.4.6 IntegerTrigger - Ambiguous response when
> integerKey field is reset
> > >> https://www.web3d.org/member-only/mantis/view.php?id=1183
> > >>
> > >>> Suggested clarification to ensure consistent implementations and
> expectations: append
> > >>> "Resetting the integerKey field generates a corresponding integerKey
> field output event."
> > >>
> > >> also related:
> > >>
> > >> [8.2] Mantis 1182: 30.4.3 BooleanToggle - Ambiguous response when
> toggle field is reset
> > >> https://www.web3d.org/member-only/mantis/view.php?id=1182
> > >>
> > >>> "Resetting the toggle field generates a corresponding toggle field
> output event."
> > >>
> > >> Absent objections, we plan to apply all of these related
> simple/sensible clarifications to X3D4 specification prose.
> > >>
> > >> ---
> > >>
> > >> h. HTML guidelines
> > >>
> > >> Draft still pending, initial entries have started.
> > >>
> > >> *
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD3/Part01/htmlGuidelines.html
> > >>
> > >> More to follow on mailing list.
> > >>
> > >> ---
> > >>
> > >> i. Field name consistency
> > >>
> > >> The possibility of synonym names for inconsistently named X3D3 fields
> looks to provide an excellent opportunity to regularize X3D4 scene graph
> for new authors, HTML5 X3D models, etc. without unintended loss of
> backwards compatibility.
> > >>
> > >> [8.0] [x3d-public] X3D4 finalization endgame: Field naming
> reconciliation as synonyms
> > >>
> https://web3d.org/pipermail/x3d-public_web3d.org/2020-November/014125.html
> > >>
> > >> Agree with Andreas note that GeoLOD should not have a synonym field
> for children since accessType is different. Others appear feasible and
> deserve close checking based on rationale.
> > >>
> > >> This does not appear to be everyone's first preference, but does
> appear to be feasible (i.e. "can live with it").
> > >>
> > >> Dick is preparing general prose regarding synonyms for section 4
> Concepts.
> > >>
> > >> Previously attached to agenda was screenshot of how specification
> format for affected node interfaces might change. We reviewed this draft
> during meeting, details below.
> > >>
> > >> [8.2] X3D4 32.4.2 CADFace
> > >>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD3/Part01/components/CADGeometry.html#CADFace
> > >>
> > >> Discussed that the synonym concept adds a greater burden on
> implementers, they have to be checked in multiple contexts, mixing/matching
> within a single model file is further difficult, other reasonable
> concerns. Agreed that it is a different requirement that does not exist in
> X3D3.
> > >>
> > >> Vince can "live with" field name changing, but does not expect that
> implementers will ever really apply synonyms because of added complexity.
> > >>
> > >> Strictly speaking, the "call for consensus" was for field name
> changing. That is what people said they could live with.
> > >>
> > >> There are too many implications associated with synonyms to be sorted
> out in short order as we try to finish. So we won't do synonyms (though
> nothing prevents an implementation from utilizing that design path if they
> like).
> > >>
> > >> Last last call, revisit next week. For those who haven't answered
> "can I live with it" a response is welcome.
> > >>
> > >> ---
> > >>
> > >> 2. Specification release timing.
> > >>
> > >> Group discussion. Looks like we need one more week.
> > >>
> > >> Additional items welcome. Are any other finals steps needed to be
> ready to ship X3D4 for Web3D Consortium member ballot and Board of
> Directors approval? We discussed details. Appears like we simply need to
> finish, all preparations for Web3D Consortium are in place.
> > >>
> > >> [9] Web3D Standards Adoption Process
> > >> https://www.web3d.org/standards/adoption-process
> > >>
> > >> ---
> > >>
> > >> Having too much fun with X3D4 maybe... finish line almost here.
> > >>
> > >> 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
> > >>
> > >>
> > >> _______________________________________________
> > >> x3d-public mailing list
> > >> x3d-public at web3d.org
> > >> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
> >
> > 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
>
> _______________________________________________
> x3d-public mailing list
> x3d-public at web3d.org
> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>
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