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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