If anyone needs the expertise, I was a math and physics major in
college, am comfortable with various transformations, and can sometimes
provide clues as to how to tackle certain situations -- provided there
are stable tools that do something, anything, consistently. After an
initial exploration of vehicle and similar physics in OpenSim and
SecondLife, and finding behaviors that were not only bizarre, but
unreproducible, or seemed to change by the hour and day, I just gave up
working on that.
Still, I'm a private pilot and still have all my calculus and mechanics
books and can help with vector or matrix algebra and that sort of
thing. Email me if you have a math / physics question I might be able
to help with, regarding how ACTUAL objects behave in REALISTIC
worlds. I can't help on why script commands don't do what they
should, if you can even figure out what it was they were hoping to do in
the first place.
Wade / "Starlight Harbour" in Jokaydia, OSgrid, Kitely, Unity, and
Second Life.
On 6/7/12 4:30 AM, James Stallings II wrote:
I've been working with vehicle scripting on opensims now for over 4
years. There are lots of historical scripts I have written or adapted
from the work of others, or collaborated on with others in the OSgrid
scripting forums. These include sailing scripts, automobile scripts,
and yes, even a helicopter script. Dave Coyle said over three years
ago that my helicopter was "the most satisfying vehicle he'd ever seen
on an opensim'.
In fact, Owen Oyen and I produced the first vehicles on OSgrid
*without any vehicle functions at all*. These were sailboats that
entirely simulated 'sailboat physics' using llSetRot, llGetRot,
llApplyImpulse and friends. The boat was clunky, did not heel, moved
in anything but a smooth fashion, and was hell on the simulation. My
more 'modern' boats can be found on Littlefield region on OSgrid, as
well as a historical display documenting the work on the aquavita. The
working copies of the boats are in a vendor; those sitting at the dock
have had the scripts ripped out to reduce lag on the sim, don't take
copies of those.
Later (much later than that boat, the 'Aquavita"), I worked
extensively with Kitto Flora to get ODE implemetations of such vehicle
scripting functions working as work now. The work is imperfect, but
not all of the problems are with ODE proper; some have to do with
various math functions' implementation in opensim, and how they differ
from the same math functions as implemented in SL under havoc. The
short story is, LL's functions are broken in terms of how physics
actually dictates real-world objects behave; and the same functions
are incomplete here, as the developers who worked on them refused to
implement the broken math, and no resolution could be reached among
the devs as to how to proceed, so the functions on opensims are
incomplete and/or unfinished.
All of this is more or less ancient history. I've got many very simple
test objects needed to reproduce these errors as test cases in
inventory on the grid, and related mantis entries filed, but quite
frankly they've been ignored for so long I lost interest a couple
years back and haven't really bothered with vehicles since. Who wants
to sail a boat that doesn't heel? Who want's to fly an airplane that
has no inertia if a vector component is on the z-axis? Not to mention,
incoming physics 'fixes' often break the workarounds, with no
explanation of how to take advantage of the improvements.
It's really discouraging to be told about your now non-functional
helicopter you've been using for most of a year that 'those vehicle
functions never really worked anyway'.
One of the problems is that to make something work you have to be able
to define 'working' in a manner that lends itself to implementation by
nuts and bolts coders, and (so far) no one has presented themselves
that has that sort of exhaustive knowledge of LL's vehicle physics.
I'm not a nay-sayer; I really hope this stuff can be made to work
someday; but I long ago lost hope as I'll likely be dead and buried
before it happens at current rates of development, especially if
everyone forgets or ignores all the prior work that has been done or
that the issues raised are not so new as the users encountering them.
I'm available to help with this, as much or as little as is needed,
but you'll have to be patient with me as, at this point, I've largely
forgotten a lot of what I knew about this, having given up on going
blue in the face trying to get anyone to take notice of the issues I
was raising.
Cheers
James aka Hiro Protagonist
On Thu, Jun 7, 2012 at 4:38 AM, Bengt Falke <[email protected]
<mailto:[email protected]>> wrote:
This is getting more and more interesting for each post on the
subject......
I think it would be a good thing to collect all the relevant
information about physics and scripting in the forum so it is
available to all struggling with this. Are there still active work
going on with ODE or are our only option to find ways around the
problems or hope for the Bullet engine?
I saw in another post a reference to a OSGrid scripting forum and
I assume it is this section you are referring to (please correct
me if I am wrong):
http://forums.osgrid.org/viewforum.php?f=5&sid=d584d594240e0917e41480491af385ec
<http://forums.osgrid.org/viewforum.php?f=5&sid=d584d594240e0917e41480491af385ec>
That might anyhow be a good place to post in.
Void Pipe
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