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Repulsion between physical and other objects
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Hi,
I'm trying to build a rotating mechanism similar to
a ferris wheel. llTargetOmega should do the trick but my problem is controlling
the repulsion between the objects. For example, a hollow cylinder around a shaft
will tear itself off the shaft if you change it to physical. The repulsion
effect seems to die down at about 100-125 mm clearance.
I've left a hollow cylinder happily spinning
about a shaft with end caps, all with 125 mm clearance. I come back an hour
later and the cylinder is laying on the ground. I understand the repulsion is
provided by Havok 4 when objects interpenetrate but I'm trying to find out how
to measure it and, perhaps, control it. Also, there seems to be a friction
effect too. My full-size object just binds, it doesn't rotate at
all.
Is there any documentation on this? Should I be
trying to independently move the components rather than using spacial
contraints?
TIA
Anderson Philbin
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Re: Repulsion between physical and other objects
llTargetOmega is, to my understanding, an entirely client-side effect.
On Tue, Sep 2, 2008 at 8:45 AM, Anderson Philbin < aphilbin@...> wrote:
> Hi,
>
> I'm trying to build a rotating mechanism similar to a ferris wheel.
> llTargetOmega should do the trick but my problem is controlling the
> repulsion between the objects. For example, a hollow cylinder around a shaft
> will tear itself off the shaft if you change it to physical. The repulsion
> effect seems to die down at about 100-125 mm clearance.
>
> I've left a hollow cylinder happily spinning about a shaft with end caps,
> all with 125 mm clearance. I come back an hour later and the cylinder is
> laying on the ground. I understand the repulsion is provided by Havok 4 when
> objects interpenetrate but I'm trying to find out how to measure it and,
> perhaps, control it. Also, there seems to be a friction effect too. My
> full-size object just binds, it doesn't rotate at all.
>
> Is there any documentation on this? Should I be trying to independently move
> the components rather than using spacial contraints?
>
> TIA
>
> Anderson Philbin
> _______________________________________________
> Click here to unsubscribe or manage your list subscription:
> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>
>
--
Ron Blechner
Chief Technology Officer
Involve, Inc
www.involve3d.com
SL: Hiro Pendragon
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Re: Repulsion between physical and other objects
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Re: Repulsion between physical and other objects
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Anderson Philbin wrote:
Hi,
I'm trying to build a rotating
mechanism similar to a ferris wheel. llTargetOmega should do the trick
but my problem is controlling the repulsion between the objects. For
example, a hollow cylinder around a shaft will tear itself off the
shaft if you change it to physical. The repulsion effect seems to die
down at about 100-125 mm clearance.
I've left a hollow cylinder happily
spinning about a shaft with end caps, all with 125 mm clearance. I come
back an hour later and the cylinder is laying on the ground. I
understand the repulsion is provided by Havok 4 when objects
interpenetrate but I'm trying to find out how to measure it and,
perhaps, control it. Also, there seems to be a friction effect too. My
full-size object just binds, it doesn't rotate at all.
Is there any documentation on this?
Should I be trying to independently move the components rather than
using spacial contraints?
TIA
Anderson Philbin
Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
this means basically is that there is a 0.1m buffer between objects.
This makes the physics calculations simpler and helps prevent
interpenetrations. But it also means physical things won't really
touch. You can see this effect clearly if you rez 1 physical cube,
then rez another above it and let it drop onto the first. After they
settle you can clearly see the gap between them.
- Kelly
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Re: Repulsion between physical and other objects
Hmm, isn't it true that when Havok4 comes under pressure, it starts simplifying shapes? Does that not include making hollow things temporarily not hollow? If the scenario you're banging your head against involves hollow objects then I think that's highly likely to be the cause, unless I am misunderstanding. Sympathies and best wishes Mr. Anderson!
On Tue, Sep 2, 2008 at 11:31 AM, Kelly Linden <kelly@...> wrote:
Anderson Philbin wrote:
Hi,
I'm trying to build a rotating
mechanism similar to a ferris wheel. llTargetOmega should do the trick
but my problem is controlling the repulsion between the objects. For
example, a hollow cylinder around a shaft will tear itself off the
shaft if you change it to physical. The repulsion effect seems to die
down at about 100-125 mm clearance.
I've left a hollow cylinder happily
spinning about a shaft with end caps, all with 125 mm clearance. I come
back an hour later and the cylinder is laying on the ground. I
understand the repulsion is provided by Havok 4 when objects
interpenetrate but I'm trying to find out how to measure it and,
perhaps, control it. Also, there seems to be a friction effect too. My
full-size object just binds, it doesn't rotate at all.
Is there any documentation on this?
Should I be trying to independently move the components rather than
using spacial contraints?
TIA
Anderson Philbin
Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
this means basically is that there is a 0.1m buffer between objects.
This makes the physics calculations simpler and helps prevent
interpenetrations. But it also means physical things won't really
touch. You can see this effect clearly if you rez 1 physical cube,
then rez another above it and let it drop onto the first. After they
settle you can clearly see the gap between them.
- Kelly
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Re: Repulsion between physical and other objects
from my experience you can't trust SL2s physics engine too much, if
your goal is simply to make a ferris wheel, and not to figure out how
to
make one relying on the phys engine to do the hard work for you, you
should use lsl to keep things right
(including the position of the wheel and the seats thing (forgot the
name)
this could probably be done somewhat easily by using llMovetoTarget
to keep the wheel in place, using llRotLookAt to constantly change
it's rotation, use llMoveToTarget with some trig and some other lsl
specific math involving rotation to make the seats thingies move in a
circle staying in the right position in relation to the current
position and rotation of the wheel, and llRotLookAt to keep the seat
thingies upright (this last one and the first thing I mentioned both
should only need to run once, the llMoveToTarget for the wheel itself
would only need to be ran again if the base has been moved or rotated)
on the parts that are colliding, see if you can make the prims phantom
(it is possible to have part of a phys linkset be phantom, the trick is
to make the prim flex, and the rest of the linkset phys, before
linking, then link the two, with the phys part as root, and never touch
the phys or flex flags), since the position and rotation would be being
handled by lsl, not having to worry about the phys engine misbehaving
would be better
Brandon Lockaby escreveu:
Hmm, isn't it true that when Havok4 comes under
pressure, it starts simplifying shapes? Does that not include making
hollow things temporarily not hollow? If the scenario you're banging
your head against involves hollow objects then I think that's highly
likely to be the cause, unless I am misunderstanding. Sympathies and
best wishes Mr. Anderson!
On Tue, Sep 2, 2008 at 11:31 AM, Kelly
Linden <kelly@...>
wrote:
Anderson Philbin wrote:
Hi,
I'm trying to build a rotating
mechanism similar to a ferris wheel. llTargetOmega should do the trick
but my problem is controlling the repulsion between the objects. For
example, a hollow cylinder around a shaft will tear itself off the
shaft if you change it to physical. The repulsion effect seems to die
down at about 100-125 mm clearance.
I've left a hollow cylinder
happily
spinning about a shaft with end caps, all with 125 mm clearance. I come
back an hour later and the cylinder is laying on the ground. I
understand the repulsion is provided by Havok 4 when objects
interpenetrate but I'm trying to find out how to measure it and,
perhaps, control it. Also, there seems to be a friction effect too. My
full-size object just binds, it doesn't rotate at all.
Is there any documentation on
this?
Should I be trying to independently move the components rather than
using spacial contraints?
TIA
Anderson Philbin
Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
this means basically is that there is a 0.1m buffer between objects.
This makes the physics calculations simpler and helps prevent
interpenetrations. But it also means physical things won't really
touch. You can see this effect clearly if you rez 1 physical cube,
then rez another above it and let it drop onto the first. After they
settle you can clearly see the gap between them.
- Kelly
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Re: Repulsion between physical and other objects
The physics engine doesn't work well with machinery. Generally speaking,
I'd write in a sensor that locates a central object and uses llSetPos()
and llSetRot() to match. I did this with a rotating clock pendulum and
a swing. You can still rotate the central object and the wheel will
follow within the sensor repeat time. If the object hasn't moved (or has
only moved < .1M, say), you can easily just rotate it around where the
"shaft" would be and people can hop on and ride at will. This also frees
you from the 31-prim (including sitters!) physical prim limit since you
don't need physics, so you can make a huge one if you like. The only
hard part is remembering how to multiply / divide the quaternion
rotations ;)
G
Anderson Philbin wrote:
> Hi,
>
> I'm trying to build a rotating mechanism similar to a ferris wheel.
> llTargetOmega should do the trick but my problem is controlling the
> repulsion between the objects. For example, a hollow cylinder around a
> shaft will tear itself off the shaft if you change it to physical. The
> repulsion effect seems to die down at about 100-125 mm clearance.
>
> I've left a hollow cylinder happily spinning about a shaft with end
> caps, all with 125 mm clearance. I come back an hour later and the
> cylinder is laying on the ground. I understand the repulsion is
> provided by Havok 4 when objects interpenetrate but I'm trying to find
> out how to measure it and, perhaps, control it. Also, there seems to
> be a friction effect too. My full-size object just binds, it doesn't
> rotate at all.
>
> Is there any documentation on this? Should I be trying to
> independently move the components rather than using spacial contraints?
>
> TIA
>
> Anderson Philbin
> ------------------------------------------------------------------------
>
> _______________________________________________
> Click here to unsubscribe or manage your list subscription:
> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>
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Re: Repulsion between physical and other objects
"Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
this means basically is that there is a 0.1m buffer between objects.
This makes the physics calculations simpler and helps prevent
interpenetrations."
Hm, maybe I missed the memo... wasn't Havok4 supposed to reduce this?
On Wed, Sep 3, 2008 at 8:24 AM, G < gcanaday@...> wrote:
> The physics engine doesn't work well with machinery. Generally speaking, I'd
> write in a sensor that locates a central object and uses llSetPos() and
> llSetRot() to match. I did this with a rotating clock pendulum and a swing.
> You can still rotate the central object and the wheel will follow within the
> sensor repeat time. If the object hasn't moved (or has only moved < .1M,
> say), you can easily just rotate it around where the "shaft" would be and
> people can hop on and ride at will. This also frees you from the 31-prim
> (including sitters!) physical prim limit since you don't need physics, so
> you can make a huge one if you like. The only hard part is remembering how
> to multiply / divide the quaternion rotations ;)
>
> G
>
> Anderson Philbin wrote:
>>
>> Hi,
>> I'm trying to build a rotating mechanism similar to a ferris wheel.
>> llTargetOmega should do the trick but my problem is controlling the
>> repulsion between the objects. For example, a hollow cylinder around a shaft
>> will tear itself off the shaft if you change it to physical. The repulsion
>> effect seems to die down at about 100-125 mm clearance.
>> I've left a hollow cylinder happily spinning about a shaft with end caps,
>> all with 125 mm clearance. I come back an hour later and the cylinder is
>> laying on the ground. I understand the repulsion is provided by Havok 4 when
>> objects interpenetrate but I'm trying to find out how to measure it and,
>> perhaps, control it. Also, there seems to be a friction effect too. My
>> full-size object just binds, it doesn't rotate at all.
>> Is there any documentation on this? Should I be trying to independently
>> move the components rather than using spacial contraints?
>> TIA
>> Anderson Philbin
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Click here to unsubscribe or manage your list subscription:
>> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>>
>
> _______________________________________________
> Click here to unsubscribe or manage your list subscription:
> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>
--
Ron Blechner
Chief Technology Officer
Involve, Inc
www.involve3d.com
SL: Hiro Pendragon
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Re: Repulsion between physical and other objects
I've had to deal with making a ferris wheel in SL. Since they move
quite slowly, I just use llSetRot and llSetPos to make it rotate one
degree a second. Swiped most of the code for it from a circle building
tool. You can prolly find it at Yadni's. Gave me a 6 minute revolution
time, which is pretty nice for a ferris wheel, and was smooth enough.
Making the carriages swing would add some additional math to it, but
shouldn't be too complicated.
On Wed, Sep 3, 2008 at 5:52 AM, Ron Blechner < ron@...> wrote:
> "Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
> this means basically is that there is a 0.1m buffer between objects.
> This makes the physics calculations simpler and helps prevent
> interpenetrations."
>
> Hm, maybe I missed the memo... wasn't Havok4 supposed to reduce this?
>
> On Wed, Sep 3, 2008 at 8:24 AM, G < gcanaday@...> wrote:
>> The physics engine doesn't work well with machinery. Generally speaking, I'd
>> write in a sensor that locates a central object and uses llSetPos() and
>> llSetRot() to match. I did this with a rotating clock pendulum and a swing.
>> You can still rotate the central object and the wheel will follow within the
>> sensor repeat time. If the object hasn't moved (or has only moved < .1M,
>> say), you can easily just rotate it around where the "shaft" would be and
>> people can hop on and ride at will. This also frees you from the 31-prim
>> (including sitters!) physical prim limit since you don't need physics, so
>> you can make a huge one if you like. The only hard part is remembering how
>> to multiply / divide the quaternion rotations ;)
>>
>> G
>>
>> Anderson Philbin wrote:
>>>
>>> Hi,
>>> I'm trying to build a rotating mechanism similar to a ferris wheel.
>>> llTargetOmega should do the trick but my problem is controlling the
>>> repulsion between the objects. For example, a hollow cylinder around a shaft
>>> will tear itself off the shaft if you change it to physical. The repulsion
>>> effect seems to die down at about 100-125 mm clearance.
>>> I've left a hollow cylinder happily spinning about a shaft with end caps,
>>> all with 125 mm clearance. I come back an hour later and the cylinder is
>>> laying on the ground. I understand the repulsion is provided by Havok 4 when
>>> objects interpenetrate but I'm trying to find out how to measure it and,
>>> perhaps, control it. Also, there seems to be a friction effect too. My
>>> full-size object just binds, it doesn't rotate at all.
>>> Is there any documentation on this? Should I be trying to independently
>>> move the components rather than using spacial contraints?
>>> TIA
>>> Anderson Philbin
>>> ------------------------------------------------------------------------
>>>
>>> _______________________________________________
>>> Click here to unsubscribe or manage your list subscription:
>>> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>>>
>>
>> _______________________________________________
>> Click here to unsubscribe or manage your list subscription:
>> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>>
>
>
>
> --
> Ron Blechner
> Chief Technology Officer
> Involve, Inc
> www.involve3d.com
> SL: Hiro Pendragon
> _______________________________________________
> Click here to unsubscribe or manage your list subscription:
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Re: Repulsion between physical and other objects
We had hoped to be able to lower the collision tolerance but have not.
Havok4 in the end gives us a lot of potential for optimization and
control that we didn't have with Havok1, and in many ways it is
inherently faster. However lowering the collision tolerance has a huge
impact on the computational load of collisions and is not something we
can just lower. Perhaps in the future after more optimizations have
been made it is something we could consider. However given the
disproportionate cost of lowering it to the benefit in most cases it
may be hard to ever find a time when we think the performance hit is
acceptable.
Some of us still dream of a day when estate owners get to control the
physics on their regions .... but that is not planned in the
foreseeable future. Maybe someday.
- Kelly
Ron Blechner wrote:
"Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
this means basically is that there is a 0.1m buffer between objects.
This makes the physics calculations simpler and helps prevent
interpenetrations."
Hm, maybe I missed the memo... wasn't Havok4 supposed to reduce this?
On Wed, Sep 3, 2008 at 8:24 AM, G gcanaday@... wrote:
The physics engine doesn't work well with machinery. Generally speaking, I'd
write in a sensor that locates a central object and uses llSetPos() and
llSetRot() to match. I did this with a rotating clock pendulum and a swing.
You can still rotate the central object and the wheel will follow within the
sensor repeat time. If the object hasn't moved (or has only moved < .1M,
say), you can easily just rotate it around where the "shaft" would be and
people can hop on and ride at will. This also frees you from the 31-prim
(including sitters!) physical prim limit since you don't need physics, so
you can make a huge one if you like. The only hard part is remembering how
to multiply / divide the quaternion rotations ;)
G
Anderson Philbin wrote:
Hi,
I'm trying to build a rotating mechanism similar to a ferris wheel.
llTargetOmega should do the trick but my problem is controlling the
repulsion between the objects. For example, a hollow cylinder around a shaft
will tear itself off the shaft if you change it to physical. The repulsion
effect seems to die down at about 100-125 mm clearance.
I've left a hollow cylinder happily spinning about a shaft with end caps,
all with 125 mm clearance. I come back an hour later and the cylinder is
laying on the ground. I understand the repulsion is provided by Havok 4 when
objects interpenetrate but I'm trying to find out how to measure it and,
perhaps, control it. Also, there seems to be a friction effect too. My
full-size object just binds, it doesn't rotate at all.
Is there any documentation on this? Should I be trying to independently
move the components rather than using spacial contraints?
TIA
Anderson Philbin
------------------------------------------------------------------------
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Re: Repulsion between physical and other objects
On a related note, any chance of seeing alternatives to using the physics model for movement? For example, I'm trying to make a swing door, and it would be great to say "Turn 90 degrees over the next 3 seconds", without having to have it physical for the effect to happen server-side. Same thing for moving up/down/left/right/etc. On 3 Sep 2008, at 17:00, Kelly Linden wrote: We had hoped to be able to lower the collision tolerance but have not. Havok4 in the end gives us a lot of potential for optimization and control that we didn't have with Havok1, and in many ways it is inherently faster. However lowering the collision tolerance has a huge impact on the computational load of collisions and is not something we can just lower. Perhaps in the future after more optimizations have been made it is something we could consider. However given the disproportionate cost of lowering it to the benefit in most cases it may be hard to ever find a time when we think the performance hit is acceptable. Some of us still dream of a day when estate owners get to control the physics on their regions .... but that is not planned in the foreseeable future. Maybe someday. - Kelly Ron Blechner wrote: "Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
this means basically is that there is a 0.1m buffer between objects.
This makes the physics calculations simpler and helps prevent
interpenetrations."
Hm, maybe I missed the memo... wasn't Havok4 supposed to reduce this?
On Wed, Sep 3, 2008 at 8:24 AM, G gcanaday@... wrote:
The physics engine doesn't work well with machinery. Generally speaking, I'd
write in a sensor that locates a central object and uses llSetPos() and
llSetRot() to match. I did this with a rotating clock pendulum and a swing.
You can still rotate the central object and the wheel will follow within the
sensor repeat time. If the object hasn't moved (or has only moved < .1M,
say), you can easily just rotate it around where the "shaft" would be and
people can hop on and ride at will. This also frees you from the 31-prim
(including sitters!) physical prim limit since you don't need physics, so
you can make a huge one if you like. The only hard part is remembering how
to multiply / divide the quaternion rotations ;)
G
Anderson Philbin wrote:
Hi,
I'm trying to build a rotating mechanism similar to a ferris wheel.
llTargetOmega should do the trick but my problem is controlling the
repulsion between the objects. For example, a hollow cylinder around a shaft
will tear itself off the shaft if you change it to physical. The repulsion
effect seems to die down at about 100-125 mm clearance.
I've left a hollow cylinder happily spinning about a shaft with end caps,
all with 125 mm clearance. I come back an hour later and the cylinder is
laying on the ground. I understand the repulsion is provided by Havok 4 when
objects interpenetrate but I'm trying to find out how to measure it and,
perhaps, control it. Also, there seems to be a friction effect too. My
full-size object just binds, it doesn't rotate at all.
Is there any documentation on this? Should I be trying to independently
move the components rather than using spacial contraints?
TIA
Anderson Philbin
------------------------------------------------------------------------
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Re: Repulsion between physical and other objects
somthing I've wanted to ask a L for some time, why didn't you just make
everything look 10 centimeters bigger to start with and not have this
weird "repulsion field" around the things?
Kelly Linden escreveu:
We had hoped to be able to lower the collision tolerance but have not.
Havok4 in the end gives us a lot of potential for optimization and
control that we didn't have with Havok1, and in many ways it is
inherently faster. However lowering the collision tolerance has a huge
impact on the computational load of collisions and is not something we
can just lower. Perhaps in the future after more optimizations have
been made it is something we could consider. However given the
disproportionate cost of lowering it to the benefit in most cases it
may be hard to ever find a time when we think the performance hit is
acceptable.
Some of us still dream of a day when estate owners get to control the
physics on their regions .... but that is not planned in the
foreseeable future. Maybe someday.
- Kelly
Ron Blechner wrote:
"Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
this means basically is that there is a 0.1m buffer between objects.
This makes the physics calculations simpler and helps prevent
interpenetrations."
Hm, maybe I missed the memo... wasn't Havok4 supposed to reduce this?
On Wed, Sep 3, 2008 at 8:24 AM, G gcanaday@... wrote:
The physics engine doesn't work well with machinery. Generally speaking, I'd
write in a sensor that locates a central object and uses llSetPos() and
llSetRot() to match. I did this with a rotating clock pendulum and a swing.
You can still rotate the central object and the wheel will follow within the
sensor repeat time. If the object hasn't moved (or has only moved < .1M,
say), you can easily just rotate it around where the "shaft" would be and
people can hop on and ride at will. This also frees you from the 31-prim
(including sitters!) physical prim limit since you don't need physics, so
you can make a huge one if you like. The only hard part is remembering how
to multiply / divide the quaternion rotations ;)
G
Anderson Philbin wrote:
Hi,
I'm trying to build a rotating mechanism similar to a ferris wheel.
llTargetOmega should do the trick but my problem is controlling the
repulsion between the objects. For example, a hollow cylinder around a shaft
will tear itself off the shaft if you change it to physical. The repulsion
effect seems to die down at about 100-125 mm clearance.
I've left a hollow cylinder happily spinning about a shaft with end caps,
all with 125 mm clearance. I come back an hour later and the cylinder is
laying on the ground. I understand the repulsion is provided by Havok 4 when
objects interpenetrate but I'm trying to find out how to measure it and,
perhaps, control it. Also, there seems to be a friction effect too. My
full-size object just binds, it doesn't rotate at all.
Is there any documentation on this? Should I be trying to independently
move the components rather than using spacial contraints?
TIA
Anderson Philbin
------------------------------------------------------------------------
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Re: Repulsion between physical and other objects
The amount of that 10cm range that's used is not consistent. You can
envision that 10cm zone as a sort of soft sponge. Objects are allowed
to interpenetrate anywhere within that range but still be considered
at rest. This helps complex arrangements - such as piles of objects or
long rows of prims - find stasis much more quickly and with fewer
server resources.
If objects were made as large as that tolerance region, you would see
them intersecting to various degrees.
On Wed, Sep 3, 2008 at 11:42 AM, Tigro Spottystripes
< tigrospottystripes@...> wrote:
> somthing I've wanted to ask a L for some time, why didn't you just make
> everything look 10 centimeters bigger to start with and not have this weird
> "repulsion field" around the things?
>
> Kelly Linden escreveu:
>
> We had hoped to be able to lower the collision tolerance but have not.
> Havok4 in the end gives us a lot of potential for optimization and control
> that we didn't have with Havok1, and in many ways it is inherently faster.
> However lowering the collision tolerance has a huge impact on the
> computational load of collisions and is not something we can just lower.
> Perhaps in the future after more optimizations have been made it is
> something we could consider. However given the disproportionate cost of
> lowering it to the benefit in most cases it may be hard to ever find a time
> when we think the performance hit is acceptable.
>
> Some of us still dream of a day when estate owners get to control the
> physics on their regions .... but that is not planned in the foreseeable
> future. Maybe someday.
>
> - Kelly
>
> Ron Blechner wrote:
>
> "Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
> this means basically is that there is a 0.1m buffer between objects.
> This makes the physics calculations simpler and helps prevent
> interpenetrations."
>
> Hm, maybe I missed the memo... wasn't Havok4 supposed to reduce this?
>
> On Wed, Sep 3, 2008 at 8:24 AM, G < gcanaday@...> wrote:
>
>
> The physics engine doesn't work well with machinery. Generally speaking, I'd
> write in a sensor that locates a central object and uses llSetPos() and
> llSetRot() to match. I did this with a rotating clock pendulum and a swing.
> You can still rotate the central object and the wheel will follow within the
> sensor repeat time. If the object hasn't moved (or has only moved < .1M,
> say), you can easily just rotate it around where the "shaft" would be and
> people can hop on and ride at will. This also frees you from the 31-prim
> (including sitters!) physical prim limit since you don't need physics, so
> you can make a huge one if you like. The only hard part is remembering how
> to multiply / divide the quaternion rotations ;)
>
> G
>
> Anderson Philbin wrote:
>
>
> Hi,
> I'm trying to build a rotating mechanism similar to a ferris wheel.
> llTargetOmega should do the trick but my problem is controlling the
> repulsion between the objects. For example, a hollow cylinder around a shaft
> will tear itself off the shaft if you change it to physical. The repulsion
> effect seems to die down at about 100-125 mm clearance.
> I've left a hollow cylinder happily spinning about a shaft with end caps,
> all with 125 mm clearance. I come back an hour later and the cylinder is
> laying on the ground. I understand the repulsion is provided by Havok 4 when
> objects interpenetrate but I'm trying to find out how to measure it and,
> perhaps, control it. Also, there seems to be a friction effect too. My
> full-size object just binds, it doesn't rotate at all.
> Is there any documentation on this? Should I be trying to independently
> move the components rather than using spacial contraints?
> TIA
> Anderson Philbin
> ------------------------------------------------------------------------
>
> _______________________________________________
> Click here to unsubscribe or manage your list subscription:
> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>
>
>
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>
>
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Re: Repulsion between physical and other objects
Somebody asked Andrew Linden this question before, and he said something
along the lines that making things appear 10cm larger would only work
for convex objects. For something like a hollow pathcut sphere, scaling
the collision body to match the rendered size wouldn't work.
Tigro Spottystripes wrote:
> somthing I've wanted to ask a L for some time, why didn't you just
> make everything look 10 centimeters bigger to start with and not have
> this weird "repulsion field" around the things?
>
> Kelly Linden escreveu:
>> We had hoped to be able to lower the collision tolerance but have
>> not. Havok4 in the end gives us a lot of potential for optimization
>> and control that we didn't have with Havok1, and in many ways it is
>> inherently faster. However lowering the collision tolerance has a
>> huge impact on the computational load of collisions and is not
>> something we can just lower. Perhaps in the future after more
>> optimizations have been made it is something we could consider.
>> However given the disproportionate cost of lowering it to the benefit
>> in most cases it may be hard to ever find a time when we think the
>> performance hit is acceptable.
>>
>> Some of us still dream of a day when estate owners get to control the
>> physics on their regions .... but that is not planned in the
>> foreseeable future. Maybe someday.
>>
>> - Kelly
>>
>> Ron Blechner wrote:
>>> "Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
>>> this means basically is that there is a 0.1m buffer between objects.
>>> This makes the physics calculations simpler and helps prevent
>>> interpenetrations."
>>>
>>> Hm, maybe I missed the memo... wasn't Havok4 supposed to reduce this?
>>>
>>> On Wed, Sep 3, 2008 at 8:24 AM, G < gcanaday@...> wrote:
>>>
>>>> The physics engine doesn't work well with machinery. Generally speaking, I'd
>>>> write in a sensor that locates a central object and uses llSetPos() and
>>>> llSetRot() to match. I did this with a rotating clock pendulum and a swing.
>>>> You can still rotate the central object and the wheel will follow within the
>>>> sensor repeat time. If the object hasn't moved (or has only moved < .1M,
>>>> say), you can easily just rotate it around where the "shaft" would be and
>>>> people can hop on and ride at will. This also frees you from the 31-prim
>>>> (including sitters!) physical prim limit since you don't need physics, so
>>>> you can make a huge one if you like. The only hard part is remembering how
>>>> to multiply / divide the quaternion rotations ;)
>>>>
>>>> G
>>>>
>>>> Anderson Philbin wrote:
>>>>
>>>>> Hi,
>>>>> I'm trying to build a rotating mechanism similar to a ferris wheel.
>>>>> llTargetOmega should do the trick but my problem is controlling the
>>>>> repulsion between the objects. For example, a hollow cylinder around a shaft
>>>>> will tear itself off the shaft if you change it to physical. The repulsion
>>>>> effect seems to die down at about 100-125 mm clearance.
>>>>> I've left a hollow cylinder happily spinning about a shaft with end caps,
>>>>> all with 125 mm clearance. I come back an hour later and the cylinder is
>>>>> laying on the ground. I understand the repulsion is provided by Havok 4 when
>>>>> objects interpenetrate but I'm trying to find out how to measure it and,
>>>>> perhaps, control it. Also, there seems to be a friction effect too. My
>>>>> full-size object just binds, it doesn't rotate at all.
>>>>> Is there any documentation on this? Should I be trying to independently
>>>>> move the components rather than using spacial contraints?
>>>>> TIA
>>>>> Anderson Philbin
>>>>> ------------------------------------------------------------------------
>>>>>
>>>>> _______________________________________________
>>>>> Click here to unsubscribe or manage your list subscription:
>>>>> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>>>>>
>>>>>
>>>> _______________________________________________
>>>> Click here to unsubscribe or manage your list subscription:
>>>> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>>>>
>>>>
>>>
>>>
>>>
>>>
>>
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>>
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Re: Repulsion between physical and other objects
I've done a good deal of tinkering with physical mechanical objects,
and I can vouch that all the "interesting" effects happen with concave
and hollow objects. For example, make a hollow cylinder, and set it
upright. Then make a physical disk just small enough to fit into the
top of the open cylinder allowing for collision tolerance, and tall
enough to keep the disk from rotating very far in the tube -- in other
words, a piston. Drop the piston into the tube, and it will "seize
up" halfway down the tube for no obvious reason. You have to make the
piston quite remarkably small before it can fall past that halfway
point.
It would be nice if the real, detailed rules of Havok4 physics were
documented somewhere. Are they?
On Wed, Sep 3, 2008 at 10:55 AM, Chip McArtor < mcm262@...> wrote:
> Somebody asked Andrew Linden this question before, and he said something
> along the lines that making things appear 10cm larger would only work for
> convex objects. For something like a hollow pathcut sphere, scaling the
> collision body to match the rendered size wouldn't work.
>
> Tigro Spottystripes wrote:
>>
>> somthing I've wanted to ask a L for some time, why didn't you just make
>> everything look 10 centimeters bigger to start with and not have this weird
>> "repulsion field" around the things?
>>
>> Kelly Linden escreveu:
>>>
>>> We had hoped to be able to lower the collision tolerance but have not.
>>> Havok4 in the end gives us a lot of potential for optimization and control
>>> that we didn't have with Havok1, and in many ways it is inherently faster.
>>> However lowering the collision tolerance has a huge impact on the
>>> computational load of collisions and is not something we can just lower.
>>> Perhaps in the future after more optimizations have been made it is
>>> something we could consider. However given the disproportionate cost of
>>> lowering it to the benefit in most cases it may be hard to ever find a time
>>> when we think the performance hit is acceptable.
>>>
>>> Some of us still dream of a day when estate owners get to control the
>>> physics on their regions .... but that is not planned in the foreseeable
>>> future. Maybe someday.
>>>
>>> - Kelly
>>>
>>> Ron Blechner wrote:
>>>>
>>>> "Havok (our physics engine) uses a Collision Tolerance of 0.1m. What
>>>> this means basically is that there is a 0.1m buffer between objects.
>>>> This makes the physics calculations simpler and helps prevent
>>>> interpenetrations."
>>>>
>>>> Hm, maybe I missed the memo... wasn't Havok4 supposed to reduce this?
>>>>
>>>> On Wed, Sep 3, 2008 at 8:24 AM, G < gcanaday@...> wrote:
>>>>
>>>>>
>>>>> The physics engine doesn't work well with machinery. Generally
>>>>> speaking, I'd
>>>>> write in a sensor that locates a central object and uses llSetPos() and
>>>>> llSetRot() to match. I did this with a rotating clock pendulum and a
>>>>> swing.
>>>>> You can still rotate the central object and the wheel will follow
>>>>> within the
>>>>> sensor repeat time. If the object hasn't moved (or has only moved <
>>>>> .1M,
>>>>> say), you can easily just rotate it around where the "shaft" would be
>>>>> and
>>>>> people can hop on and ride at will. This also frees you from the
>>>>> 31-prim
>>>>> (including sitters!) physical prim limit since you don't need physics,
>>>>> so
>>>>> you can make a huge one if you like. The only hard part is remembering
>>>>> how
>>>>> to multiply / divide the quaternion rotations ;)
>>>>>
>>>>> G
>>>>>
>>>>> Anderson Philbin wrote:
>>>>>
>>>>>>
>>>>>> Hi,
>>>>>> I'm trying to build a rotating mechanism similar to a ferris wheel.
>>>>>> llTargetOmega should do the trick but my problem is controlling the
>>>>>> repulsion between the objects. For example, a hollow cylinder around a
>>>>>> shaft
>>>>>> will tear itself off the shaft if you change it to physical. The
>>>>>> repulsion
>>>>>> effect seems to die down at about 100-125 mm clearance.
>>>>>> I've left a hollow cylinder happily spinning about a shaft with end
>>>>>> caps,
>>>>>> all with 125 mm clearance. I come back an hour later and the cylinder
>>>>>> is
>>>>>> laying on the ground. I understand the repulsion is provided by Havok
>>>>>> 4 when
>>>>>> objects interpenetrate but I'm trying to find out how to measure it
>>>>>> and,
>>>>>> perhaps, control it. Also, there seems to be a friction effect too. My
>>>>>> full-size object just binds, it doesn't rotate at all.
>>>>>> Is there any documentation on this? Should I be trying to
>>>>>> independently
>>>>>> move the components rather than using spacial contraints?
>>>>>> TIA
>>>>>> Anderson Philbin
>>>>>>
>>>>>> ------------------------------------------------------------------------
>>>>>>
>>>>>> _______________________________________________
>>>>>> Click here to unsubscribe or manage your list subscription:
>>>>>>
>>>>>> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Click here to unsubscribe or manage your list subscription:
>>>>>
>>>>> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>> ------------------------------------------------------------------------
>>>
>>> _______________________________________________
>>> Click here to unsubscribe or manage your list subscription:
>>> https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters>>>
>>
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--
Craig Berry - http://www.cine.net/~cberry/"Pie is a bit of a fair-weather friend when it
comes to walls." -- Lenore Berry
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Re: Repulsion between physical and other objects
It seems to me if they *could* just make everything 10cm bigger and
everything would work, they *could* have just made the minimum size be
10cm bigger not not have a "repulsion field" at all. However, from
what Chip said he heard from Andrew, it does not appear the 10cm is a
fixed distance out from the surface of the object, but rather,
provides a certain amount of smoothing and may be different distances
depending on the geometry of the object. Also, from what Kelly noted,
it sounds like this is also a buffer zone which allows the physics
engine to have a time window in which to catch the object. If an
object is moving less than 4.5 m/s (270 kph, ~165mph) relative to
another object and the physics frame rate is 45 fps, then it will not
move more than 0.1 m per frame (10 cm) and you can catch the objects
prior to them intersecting one another rather than potentially after
penetration.
I do enjoy the earlier comment about how the engine will simplify
things under pressure. The world is an interesting place when the laws
of physics can change around you :-)
Kubota
"Using heavy machinery for delicate tasks"
On Sep 3, 2008, at 12:55 PM, Chip McArtor wrote:
> Somebody asked Andrew Linden this question before, and he said
> something along the lines that making things appear 10cm larger
> would only work for convex objects. For something like a hollow
> pathcut sphere, scaling the collision body to match the rendered
> size wouldn't work.
>
> Tigro Spottystripes wrote:
>> somthing I've wanted to ask a L for some time, why didn't you just
>> make everything look 10 centimeters bigger to start with and not
>> have this weird "repulsion field" around the things?
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Re: Repulsion between physical and other objects
I guess later I'll post an entry on Jira asking for a hidden option to
display the collision buffer mesh instead of the visual mesh, in my head
interpenetration would look less bad than floating stuff, but I dunno
how it would actually be like in practice
Kubota Homewood escreveu:
> It seems to me if they *could* just make everything 10cm bigger and
> everything would work, they *could* have just made the minimum size be
> 10cm bigger not not have a "repulsion field" at all. However, from
> what Chip said he heard from Andrew, it does not appear the 10cm is a
> fixed distance out from the surface of the object, but rather,
> provides a certain amount of smoothing and may be different distances
> depending on the geometry of the object. Also, from what Kelly noted,
> it sounds like this is also a buffer zone which allows the physics
> engine to have a time window in which to catch the object. If an
> object is moving less than 4.5 m/s (270 kph, ~165mph) relative to
> another object and the physics frame rate is 45 fps, then it will not
> move more than 0.1 m per frame (10 cm) and you can catch the objects
> prior to them intersecting one another rather than potentially after
> penetration.
>
> I do enjoy the earlier comment about how the engine will simplify
> things under pressure. The world is an interesting place when the laws
> of physics can change around you :-)
>
> Kubota
>
> "Using heavy machinery for delicate tasks"
>
> On Sep 3, 2008, at 12:55 PM, Chip McArtor wrote:
>
>> Somebody asked Andrew Linden this question before, and he said
>> something along the lines that making things appear 10cm larger would
>> only work for convex objects. For something like a hollow pathcut
>> sphere, scaling the collision body to match the rendered size
>> wouldn't work.
>>
>> Tigro Spottystripes wrote:
>>> somthing I've wanted to ask a L for some time, why didn't you just
>>> make everything look 10 centimeters bigger to start with and not
>>> have this weird "repulsion field" around the things?
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Re: Repulsion between physical and other objects
Something to bear in mind here is that smoothness
of movement is surprisingly subjective.
Recently, I made a swing for my partner and
started off using llSetRot() to make it happen,
but couldn't get it smooth enough for my own
tastes - using it was actually nauseating for
me. My partner, however, was perfectly happy
with the movement. I was not. Since this was a
labour of love rather than Lindens, I kept
investigating - people I spoke to who'd made
swings (all using the same method with varying
parameters) were adamant that their swings were
"smooth" - I, on the other hand, found every one
of these swings to be very unpleasant to use,
rather to their builders' bafflement. Impasse.
In the end, I changed the movement in my own
swing to use llTargetOmega() and was delighted to
find it completely free from any jerkiness. My
partner kind of agreed that it was a better
experience and we started to use the swing a lot
more.
Now, whenever we come across a swing or a hammock
in our SL travels, it is she as much as me who
remarks that the swing at home is far more
pleasant to use. Meanwhile, the builders of
llSetRot() systems continue to be perfectly happy
with their own creations. It's incredible how
subjective it is, and what is fine to one person
can actually be genuinely unpleasant,
even nauseating, to another.
I'd be very interested to visit your llSetRot()
Ferris wheel in-world, to see if I could ride it
without feeling ill, and to compare notes with
someone who found the movement fine to use; I
find it hard to believe that the difference is
purely psychological, and wonder if it's to do
with different hardware.
On Wed, 3 Sep 2008 07:09:38 -0700
Jippen < cheetahmorph@...> wrote:
> I've had to deal with making a ferris wheel in
> SL. Since they move quite slowly, I just use
> llSetRot and llSetPos to make it rotate one
> degree a second. Swiped most of the code for it
> from a circle building tool. You can prolly
> find it at Yadni's. Gave me a 6 minute
> revolution time, which is pretty nice for a
> ferris wheel, and was smooth enough. Making the
> carriages swing would add some additional math
> to it, but shouldn't be too complicated.
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Re: Repulsion between physical and other objects
This has probably got more to do with network issues than actual PC
differences as llSetRot changes the status of the prim server side,
which means that data needs to travel from server to client throughout
the course of the motion, whereas llTargetOmega primarily client based
and so is not reliant on network traffic conditions. Network being the
servers own netwrok, the bandwidth from the server to teh Internet, and
the connection from your own PC through your ISP to the server as well.
Barrington John wrote:
> Something to bear in mind here is that smoothness
> of movement is surprisingly subjective.
>
> Recently, I made a swing for my partner and
> started off using llSetRot() to make it happen,
> but couldn't get it smooth enough for my own
> tastes - using it was actually nauseating for
> me. My partner, however, was perfectly happy
> with the movement. I was not. Since this was a
> labour of love rather than Lindens, I kept
> investigating - people I spoke to who'd made
> swings (all using the same method with varying
> parameters) were adamant that their swings were
> "smooth" - I, on the other hand, found every one
> of these swings to be very unpleasant to use,
> rather to their builders' bafflement. Impasse.
>
> In the end, I changed the movement in my own
> swing to use llTargetOmega() and was delighted to
> find it completely free from any jerkiness. My
> partner kind of agreed that it was a better
> experience and we started to use the swing a lot
> more.
>
> Now, whenever we come across a swing or a hammock
> in our SL travels, it is she as much as me who
> remarks that the swing at home is far more
> pleasant to use. Meanwhile, the builders of
> llSetRot() systems continue to be perfectly happy
> with their own creations. It's incredible how
> subjective it is, and what is fine to one person
> can actually be genuinely unpleasant,
> even nauseating, to another.
>
> I'd be very interested to visit your llSetRot()
> Ferris wheel in-world, to see if I could ride it
> without feeling ill, and to compare notes with
> someone who found the movement fine to use; I
> find it hard to believe that the difference is
> purely psychological, and wonder if it's to do
> with different hardware.
>
> On Wed, 3 Sep 2008 07:09:38 -0700
> Jippen < cheetahmorph@...> wrote:
>
>
>> I've had to deal with making a ferris wheel in
>> SL. Since they move quite slowly, I just use
>> llSetRot and llSetPos to make it rotate one
>> degree a second. Swiped most of the code for it
>> from a circle building tool. You can prolly
>> find it at Yadni's. Gave me a 6 minute
>> revolution time, which is pretty nice for a
>> ferris wheel, and was smooth enough. Making the
>> carriages swing would add some additional math
>> to it, but shouldn't be too complicated.
>>
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Re: Repulsion between physical and other objects
llTargetOmega for a swing? Did you use a timer to reverse the axes used
in the rotation at the end of a swing?
The reason I chose llSetRot for the one I made for my partner is because
I needed it to follow the swing frame when I moved it, and it's far
easier to do the math to make the swing agree with the frame using
rotations than it is to determine which axis has to move how far in an
automated rot, imo. llTargetOmega is smoother, yes... but I've only used
it for continually rotating objects, myself.
G
Barrington John wrote:
> Something to bear in mind here is that smoothness
> of movement is surprisingly subjective.
>
> Recently, I made a swing for my partner and
> started off using llSetRot() to make it happen,
> but couldn't get it smooth enough for my own
> tastes - using it was actually nauseating for
> me. My partner, however, was perfectly happy
> with the movement. I was not. Since this was a
> labour of love rather than Lindens, I kept
> investigating - people I spoke to who'd made
> swings (all using the same method with varying
> parameters) were adamant that their swings were
> "smooth" - I, on the other hand, found every one
> of these swings to be very unpleasant to use,
> rather to their builders' bafflement. Impasse.
>
> In the end, I changed the movement in my own
> swing to use llTargetOmega() and was delighted to
> find it completely free from any jerkiness. My
> partner kind of agreed that it was a better
> experience and we started to use the swing a lot
> more.
>
> Now, whenever we come across a swing or a hammock
> in our SL travels, it is she as much as me who
> remarks that the swing at home is far more
> pleasant to use. Meanwhile, the builders of
> llSetRot() systems continue to be perfectly happy
> with their own creations. It's incredible how
> subjective it is, and what is fine to one person
> can actually be genuinely unpleasant,
> even nauseating, to another.
>
> I'd be very interested to visit your llSetRot()
> Ferris wheel in-world, to see if I could ride it
> without feeling ill, and to compare notes with
> someone who found the movement fine to use; I
> find it hard to believe that the difference is
> purely psychological, and wonder if it's to do
> with different hardware.
>
> On Wed, 3 Sep 2008 07:09:38 -0700
> Jippen < cheetahmorph@...> wrote:
>
>
>> I've had to deal with making a ferris wheel in
>> SL. Since they move quite slowly, I just use
>> llSetRot and llSetPos to make it rotate one
>> degree a second. Swiped most of the code for it
>> from a circle building tool. You can prolly
>> find it at Yadni's. Gave me a 6 minute
>> revolution time, which is pretty nice for a
>> ferris wheel, and was smooth enough. Making the
>> carriages swing would add some additional math
>> to it, but shouldn't be too complicated.
>>
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smime.p7s (4K) 