[Opensim-dev] Negative z values

[drWhiet]

besides everything said, this nails it down : "... but declaring the
Metaverse to simply end at 0 seems very random. "
I should make this my new email signature .. well said, Jim  .. it's the
metaverse .. no boundaries ? with future physics
not working below -0 ther will be no underwater worlds .. no submarines ..
even boat creators must keep an eye that the 
engine does not move below -0 ; ?
 
best regards
Wordfromthe Wise

  _____  

Von: opensim-dev-bounces at opensimulator.org
[mailto:opensim-dev-bounces at opensimulator.org] Im Auftrag von Jim Williams
Gesendet: Freitag, 25. April 2014 02:17
An: opensim-dev at opensimulator.org
Betreff: Re: [Opensim-dev] Negative z values


Seems to me that 0 is a completely arbitrary number and that a cut-off for
any reason other than hardware/mathematical limitations is unwarranted.  I
could see taking an "oh well" attitude about things that don't work with -z,
but declaring the Metaverse to simply end at 0 seems very random.


On Thu, Apr 24, 2014 at 6:46 PM, Melanie <melanie at t-data.com> wrote:


I have never seen a Z < 0 build. I see lots of problems that may be
possible with this, but I think that quite beautiful and interesting
builds could make use of this and would support keeping it. The
change in the viewer is recent and likely trivial to undo.

- Melanie

On 25/04/2014 00:32, Justin Clark-Casey wrote:
> Hi folks.  Historically, whether by accident or design, OpenSimulator has
allowed negative Z values for terrain, objects
> and avatars (e.g. <130, 50, -45>.  I have seen people use this facility to
build fully underwater or partially
> underwater structures (e.g. oil rigs, sunken ships, etc.) which are
conceptually far below the water line without having
> to set that water line at a level that may be way above that of
surrounding regions.
>
> However, at least on Singularity 1.8.5 on Linux, fog effects do not work
properly when z < 0, where all view distances
> have very high fog no matter what the fog settings.  This may be a recent
change - I remember fog working properly at
> negative z values in the past, though the fog issue still occurred past a
certain -ve z.  There may be other issues of
> which I'm not aware.  Arguably, these are not bugs since the Linden Grid
does not allow z < 0 (though one could make the
> same argument for var regions, etc.).
>
> With in-world testing of current development code, BulletSim appears to
have a hard-coded check where I can't move my
> avatar below z == 2 whether terrain is z < 0 or not (this should probably
at least be fixed so z = 0 is possible).  ODE
> has allowed and still allows the avatar to descend to negative depths.
>
> One argument is that in the light of such bugs, it would be better to
consistently enforce z >= 0 and require people
> with -z builds to either move them and the water level up using
OpenSimulator commands (e.g. "translate scene") or never
> update their OpenSimulator installation.
>
> However, I think there is a real value in keeping the -ve z ability.  It
allows people to extend deep water builds
> without having to adjust any neighbouring sims for consistency (which they
may not have control over).  I'm sure it's
> possible to address the viewer-side issues.  OpenSimulator could have an
allow-negative-z flag which is false by default
> to make it explicit that using -ve z may have issues at this time.  I
accept this is a more complicated solution than
> enforcing z == 0, though enforcing z == 0 will also requires many changes
to the current code where bounds are not checked.
>
> If my experience is unusual and -z builds are very rare then there's more
of a case for enforcing z >= 0.
>
> Thoughts?
>
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