[x3d-public] ambientIntensity [0, 1] or unbounded [0, infinity) ?

[John Carlson]

After reading through Michalis’ arguments, I am reminded of High Dynamic
Range (HDR), but I don’t know of any applicability to X3D (anyone?).

John

On Fri, Apr 29, 2022 at 5:49 AM Michalis Kamburelis <
michalis.kambi at gmail.com> wrote:

> Hm, good point. To be honest we can go either way for me.
>
> It doesn't matter that much because
>
> A. ambientIntensity is ignored by PBR model (PhysicalMaterial) that
> doesn't have a concept of "ambient" at all. (This is stated explicitly
> in spec, """In the physical lighting model, the ambientIntensity value
> is unused. """)
>
> B. In most practical cases, even with Phong (Material), people should
> not use too large ambientIntensity values. The ambient and
> ambientIntensity in Phong are already somewhat "unrealistic cheat"
> (that is, you just bump the final color to simulate global
> illumination; that's as naive implementation of "global illumination"
> as you can get :) ).
>
> So likely authors don't need to use values for ambientIntensity > 1.
> But then, there's nothing in Phong lighting equations that really
> prevents bigger ambientIntensity values.
>
> So, ways to go:
>
> 1. Ignore, i.e. leave ambientIntensity in [0,1]. Just because there's
> no practical reason to change it.
>
> 2. Or make ambientIntensity unbounded like intensity, i.e. allow
> [0,infinity].
>
> For me, the only real advantage of AD 2 solution is that it will make
> ambientintensity consistent with intensity. But that's not a big gain
> -- ultimately ambientIntensity and intensity are just completely
> different concepts, they just happen to share a common name. The
> "intensity" has a physical interpretation (that we put in spec) and
> works with all lighting models. "ambientIntensity" is a "cheat' and
> only available in Phong lighting model.
>
> So I would choose solution AD 1 (do nothing) just because there's no
> real need (from authors' perspective) to remove the limit, from what I
> know. But both AD 1 and AD 2 resolutions are acceptable for me.
>
> Regards,
> Michalis
>
> pt., 29 kwi 2022 o 02:53 Brutzman, Donald (Don) (CIV)
> <brutzman at nps.edu> napisał(a):
> >
> > Hi Michalis.  We’re looking at
> >
> >
> >
> > Mantis 130: 17.2.2: Lighting Max Values
> > https://www.web3d.org/member-only/mantis/view.php?id=130
> >
> >
> >
> > Most light intensity-related fields (but not all) are now unbounded.
> The intensity field is [0,infinity)
> >
> > Not quite sure about ambientIntensity bounds, which are currently [0,1]
> and thus not unconstrained like intensity.
> >
> >
> >
> > Please advise what you think, TIA.
> >
> >
> >
> > 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
> >
> >
>
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