[ODE] Increasing number of particales changes physics

[Roland Kindermann]

I was rather thinking about collision detection. I think, it should in 
most cases be much faster, to test, whether a point is inside a volume, 
than to check, whether to volumes intersect. Also calculating normal and 
depth should be faster. Or am I wrong?
Cheers,
Roland Kindermann

Megan Fox schrieb:
> This may be obtuse, but I'm curious about something... joint
> contraints work by removing axis of freedom from a given object,
> constraining them to a particular orientation or region.  As I
> understand it, the more constraints, the faster the joint and less
> amount of impact on the sim speed.
> 
> Given that, would it be possible to make a "point" contact joint that
> acted to correct the position of the body in question, but with fewer
> axis of freedom (eg. no rotation), thereby acting faster than a
> traditional contact joint?
> 
> 
> Seemingly, you'd use the same collider either way (unless the collider
> is doing something odd a sphere and a point collision should be doing
> the same thing - which is to say, not much really, radius + center
> point), but this would be the difference between a point and a sphere?
> 
> On 8/12/06, Roland Kindermann <iyo at gmx.de> wrote:
>> Hi,
>> I work with particles too. I think it would be nice to have a Point
>> Geometry (which only consists of one point) for particles. It would
>> probably be faster than a small Sphere.
>> Cheers,
>> Roland Kindermann
>>
>> Jacob Ole Juul Kolding schrieb:
>> > OK I have a fixed step time and that works fine.
>> >
>> > The next problem is when I enable collision (So that the particles
>> > bounce against a floor). When the simulation has up to 350 particles it
>> > seem to run smoothly and stable, but above 350 it will eventually 
>> suffer
>> > a slowdown death causing the app to be unresponsive.
>> >
>> > I switched to HashSpace and set the category/collide bits so that the
>> > particles should not collide with each other but only the floor.
>> >
>> > Is this a bottleneck?
>> >
>> > /Jacob Kolding
>> >
>> >
>> > On 8/11/06, *Jon Watte* <hplus at mindcontrol.org
>> > <mailto:hplus at mindcontrol.org>> wrote:
>> >
>> >     Correct. You need to use a fixed time step. Such as in
>> >     http://www.mindcontrol.org/~hplus/graphics/game_loop.html
>> >     <http://www.mindcontrol.org/%7Ehplus/graphics/game_loop.html>
>> >
>> >     Jacob Ole Juul Kolding wrote:
>> >     >  I'm implementing a particle system in ODE and have 
>> encountered the
>> >     >  problem that when the number of particles increase the 
>> physics change
>> >     >  in the the way the even though the same force is applied, the 
>> more
>> >     >  particles are in the simulation the longer they will travel.
>> >     >
>> >     >  My guess is that since i step the world each frame, when the 
>> frame
>> >     >  rate drops the step time increase which changes the outcome 
>> of the
>> >     >  simulation?
>> >     >
>> >     >  Anyone have an idea how to help this problem?
>> >     >
>> >     >  /Jacob Kolding
>> >     >
>> >     
>> ------------------------------------------------------------------------
>> >     >
>> >     >  _______________________________________________
>> >     >  ODE mailing list
>> >     >  ODE at q12.org <mailto:ODE at q12.org>
>> >     >  http://q12.org/mailman/listinfo/ode
>> >     >
>> >
>> >
>> >
>> > 
>> ------------------------------------------------------------------------
>> >
>> > _______________________________________________
>> > ODE mailing list
>> > ODE at q12.org
>> > http://q12.org/mailman/listinfo/ode
>>
>> _______________________________________________
>> ODE mailing list
>> ODE at q12.org
>> http://q12.org/mailman/listinfo/ode
>>
> 
>