[Opensim-dev] Negative z values

[Mic Bowman]

do the viewers support that granularity of water height? that would be very
useful if it could be made to work.

--mic



On Thu, Apr 24, 2014 at 5:23 PM, Melanie <melanie at t-data.com> wrote:

> There are potential issues with code/tools written with the notion
> that the metaverse indeed ends at 0, but I believe they can be overcome.
> In this vein, there is another "feature" we may want to push for:
>
> Raw files allow specifying a water height for each 4x4 m square, but
> currently regions only have a notion of water level for the entire
> region, taken from the 0,0 coordinate of the water level layer in
> the raw file.
>
> I believe full support for a water height map (including Z < 0
> depths) would be an advantage of opensim over SL, as SL currently
> struggles with basements, subway tunnels and mountain lakes.
>
> - Melanie
>
> On 25/04/2014 02:16, Jim Williams wrote:
> > 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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> >>
> >
> >
> >
> >
> >
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