[x3d-public] X3D 4: Change whether ambientParameter is affected by diffuseTexture?

Wed Apr 28 03:44:30 PDT 2021

Don,

I created a Mantis issue to remember about this:
https://www.web3d.org/member-only/mantis/view.php?id=1359 . I believe
it is important to fix for X3D 4.0.

( Strangely enough, although I cannot *post comments* in Mantis, it
looks like I can create new tickets :) ).

As I emphasize there, the "fix" for the issue is rather trivial, and I
believe there's consensus to do it. I can do it in the spec myself --
just tell when it is allowed to edit the spec in GitHub.

Regards,
Michalis

sob., 10 kwi 2021 o 22:15 Don Brutzman <brutzman at nps.edu> napisał(a):
>
> Thanks for the close scrutiny and proposed fix.  Seems sensible.
>
> Might you create a simple Mantis issue describing problem and fix?
>
> In a few weeks we will be deciding which active Mantis issues will get sent to ISO prior to the early-May voting deadline for X3D4 Committee Draft.
>
> Appreciate your efforts to ensure we are fully aligned with glTF.
>
>
> On 4/8/2021 2:47 PM, Michalis Kamburelis wrote:
> >
> >
> > I am bumping this thread. Anyone has any opinion?
> >
> > I propose in my mail a fix to X3D 4 lighting equations. Due to my mistake:
> >
> > - Phong lighting is not perfectly backward-compatible to X3D 3 in one
> > case: when you provided a dark texture for diffuse in X3D 3, and
> > relied that it will also make ambient term dark.
> >
> > - It may also be a bit unnatural, as you can have a surface with black
> > diffuse texture, yet it will have a bright ambient. This is unnatural.
> >
> > In my mail I propose a simple fix for both these issues: just one
> > equation needs a very small change, in
> > https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.web3d.org%2Fspecifications%2FX3Dv4Draft%2FISO-IEC19775-1v4-WD3%2FPart01%2Fcomponents%2Flighting.html%23LightingPhong&data=04%7C01%7Cbrutzman%40nps.edu%7Ca66fbb0c66424879413508d8fad82f12%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C637535153719230930%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=0OYP7t3T%2FiS7tc6acYcCyh92lm%2FXnBT3TFQG1TuyY68%3D&reserved=0
> > :
> >
> >    ambientParameter = ambientIntensity × diffuseColor ×
> > textureSample(ambientTexture).rgb
> >
> > shoud change to
> >
> >    ambientParameter = ambientIntensity × diffuseParameter.rgb ×
> > textureSample(ambientTexture).rgb
> >
> > IOW just change "diffuseColor" to "diffuseParameter.rgb". See my first
> > email in this thread for details. Can we fix it in X3D 4.0, or is this
> > too late now?
> >
> > Regards,
> > Michalis
> >
> >
> >
> > wt., 16 mar 2021 o 08:59 Michalis Kamburelis
> > <michalis.kambi at gmail.com> napisał(a):
> >
> >>
> >> Hi,
> >>
> >> Thanks to Victor Amat, I became aware that I did break compatibility
> >> in X3D 4 light equations, compared to X3D 3 treatment of Phong
> >> Materials. The fix is very trivial if you agree, read on:
> >>
> >> In X3D 4 right now, in "17.2.2.5 Phong lighting model" (
> >> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.web3d.org%2Fspecifications%2FX3Dv4Draft%2FISO-IEC19775-1v4-WD3%2FPart01%2Fcomponents%2Flighting.html%23LightingPhong&data=04%7C01%7Cbrutzman%40nps.edu%7Ca66fbb0c66424879413508d8fad82f12%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C637535153719230930%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=0OYP7t3T%2FiS7tc6acYcCyh92lm%2FXnBT3TFQG1TuyY68%3D&reserved=0
> >> ) says that ambientParameter is calculated using ambientIntensity,
> >> diffuseColor and ambientTexture.
> >>
> >> This means that that Material.diffuseTexture and Appearance.texture
> >> *do not* affect the ambient term. Only diffuseColor does. This is
> >>
> >> - unrealistic (a normal "black body", like black velvet, should not
> >> make ambient or diffuse light -- think of what happens if you express
> >> this "black body" using a black diffuse texture)
> >>
> >> - incompatible with X3D 3. The lighting equations in X3D 3 (
> >> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.web3d.org%2Fdocuments%2Fspecifications%2F19775-1%2FV3.3%2FPart01%2Fcomponents%2Flighting.html%23Lightingequations&data=04%7C01%7Cbrutzman%40nps.edu%7Ca66fbb0c66424879413508d8fad82f12%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C637535153719230930%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=05pNX8Cc2i5QLwrhVQ4WKx8yBJGFVYlaFU%2Bz1oqVVzY%3D&reserved=0
> >> ) said that ambient_i is affected by O_Drgb which in turn is (citing)
> >> """diffuse colour, from a node derived from X3DMaterialNode,  a node
> >> derived from X3DColorNode, and/or a texture node""".
> >>
> >> The fix is extremely trivial: In
> >> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.web3d.org%2Fspecifications%2FX3Dv4Draft%2FISO-IEC19775-1v4-WD3%2FPart01%2Fcomponents%2Flighting.html%23LightingPhong&data=04%7C01%7Cbrutzman%40nps.edu%7Ca66fbb0c66424879413508d8fad82f12%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C637535153719230930%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=0OYP7t3T%2FiS7tc6acYcCyh92lm%2FXnBT3TFQG1TuyY68%3D&reserved=0
> >> ,
> >>
> >>    ambientParameter = ambientIntensity × diffuseColor ×
> >> textureSample(ambientTexture).rgb
> >>
> >> shoud change to
> >>
> >>    ambientParameter = ambientIntensity × diffuseParameter.rgb ×
> >> textureSample(ambientTexture).rgb
> >>
> >> IOW just change "diffuseColor" to "diffuseParameter.rgb". The
> >> "diffuseParameter" is defined above, it is determined by diffuseColor,
> >> diffuseTexture, possible per-vertex colors etc.
> >>
> >> What do you think?
> >>
> >> Regards,
> >> Michalis
> >
> > _______________________________________________
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> > x3d-public at web3d.org
> > https://nam10.safelinks.protection.outlook.com/?url=http%3A%2F%2Fweb3d.org%2Fmailman%2Flistinfo%2Fx3d-public_web3d.org&data=04%7C01%7Cbrutzman%40nps.edu%7Ca66fbb0c66424879413508d8fad82f12%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C637535153719240915%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=JMTRAcxSXHPBzA3%2Fd%2Bc5ijKxZ%2FXHFlnEK1bBrxMoYkU%3D&reserved=0
> >
>
> 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