[x3d-public] visibilityRange for X3DFogObject: specification erratum detected

[Brutzman, Donald (Don) (CIV)]

I have entered these excellent comments in the Mantis issue tracker as

 

*	Mantis 1444: Table 17.5 missing description of local variable
fogVisibility; table term/title errata
*	https://www.web3d.org/member-only/mantis/view.php?id=1444

 

*	Mantis 1445: 24.3.2 X3DFogObject, 24.4.4 LocalFog have incorrect
negative signum on limit for visibilityRange
*	https://www.web3d.org/member-only/mantis/view.php?id=1445

 

Dick and I are meeting with other ISO editors Monday.  The changes are
editorial, and so am hoping that these corrections can be applied now as
formal editor comments pending final ISO/IEC approval of the ISO proof
document.  If not, they will have to be a formal corrigendum or else
postponed to X3D 4.1.

 

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

 

-----Original Message-----
From: Michalis Kamburelis <michalis.kambi at gmail.com> 
Sent: Wednesday, October 18, 2023 12:29 PM
To: Andreas Plesch <andreasplesch at gmail.com>
Cc: Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>; Holger Seelig
<holger.seelig at yahoo.de>; puk at igraphics.com; X3D <x3d-public at web3d.org>
Subject: Re: [x3d-public] visibilityRange for X3DFogObject: specification
erratum detected

 

NPS WARNING: *external sender* verify before acting.

 

 

Hi,

 

I completely agree with Andreas proposed addition to define

 

"""

- fogVisibility (Table 17.5) is the currently bound fog's visibilityRange,
in the same coordinate system as fogDistance.

"""

 

> Michalis may have background on introducing the 'fogVisibility' term.

> Perhaps it is an attempt to decouple from the fog node to allow 

> flexible use of world or local coordinate systems for computations.

 

I'm afraid I don't have any additional insight as to why it is called
"fogVisibility". It was already called like that in X3D 3.3, before my PBR
edits (
<https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/componen
ts/lighting.html>
https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/component
s/lighting.html

) and it was also not explicitly defined there. So I neither broke nor
improved that state when editing that section for X3D 4.0 :) The theory
above from Andreas sounds good -- i.e. the term is called "fogVisibility" to
make it clear that it is not "just straightforward visibilityRange" value,
and instead it is "visibilityRange converted

(scaled) by the fog node transformation".

 

I believe the intention was always just like Andreas said, and it matches
CGE/view3dscene implementation too.

 

Regards,

Michalis

 

śr., 18 paź 2023 o 16:22 Andreas Plesch < <mailto:andreasplesch at gmail.com>
andreasplesch at gmail.com> napisał(a):

> 

> Hi Don,

> 

> Thanks.

> 

> > Andreas, if you have suggested prose for "explain that fogVisibility
corresponds to the visibilityRange field" then please send that.  We can at
least create a Mantis issue for eventual resolution.

> 

> The table 17.5 at

> 

>  <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-IS.pr>
https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-IS.pr

> oof/Part01/components/lighting.html#t-foginterpolant

> 

> mentions 'fogVisibility' but the term is not clearly defined.

> 

> The bullet list above the table has

> 

> - fogInterpolant is the fog interpolant, see Table 17.5 for calculation.

> - fogDistance is the distance from point on geometry to viewer's 

> position, in coordinate system of current fog node.

> - fogColor is the currently bound fog's color.

> 

> Let me suggest expanding that list with an additional line:

> 

> - fogVisibility (Table 17.5) is the currently bound fog's 

> visibilityRange, in the same coordinate system as fogDistance.

> 

> Michalis may have background on introducing the 'fogVisibility' term.

> Perhaps it is an attempt to decouple from the fog node to allow 

> flexible use of world or local coordinate systems for computations.

> 

> Best, Andreas

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