thinking particles (+ dynamics?): collision issue

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  05 May 2013
thinking particles (+ dynamics?): collision issue

hi all

Using C4D and thinking particles, I've been trying to figure out how to get irregular particle geometry to interact with deflector surfaces in a convincing way.

Spheres? no problem. Irregular shapes? They're poking through the surface, not good.

Got some recent advice on adding dynamics tags to the particle geometry, but it gives a very odd, and unnatural "laggy" collision IMO, so I'm wondering if anyone has any more tricks or settings to share on this topic.

thanks very much!


Last edited by LML : 05 May 2013 at 01:31 AM.
  05 May 2013
the deflector node is not meant to be used for accurate collision models. i am not
sure what you do mean with 'laggy' collision for a dynamics tag though. simply add
a rb dynamics tag to your particle geometry object and set it to elements>all and
shape moving mesh. the result will be pretty accurate, but you will loose the control
over your particles to some degree.
  05 May 2013
thanks for the response--and yes I believe this is how I have it set up

by "laggy" I mean this: when a particle impacts a surface and then bounces back, there is a little hop or stutter; here's a screen capture clip (sorry it's not realtime, but I think it still illustrates my point):

upping the solver samples, and the "follow position" options helps to some degree, but not completely.

Do you have another suggestion, instead of deflectors?

thanks a lot,

  05 May 2013
hm, i am still not sure what you mean by laggy, if you are referring to the frame drops
around the collision events, this is just the bullet engine struggling with live playback,
this effect should vanish for rendered or baked data (not sure how well baking plays
with TP feeding rigid body dynamics).

if you are refering with stuttering to the change of speed and self rotation after the
collision event this is just the natural outcome of the bullet solver. there are the bounce,
friction and noise values in each rbd-tag. the higher the friction value in both rbd-tags
of the participating objects in a collision event, the shorter their velocity vector will be
after the event. or in other words less speed, less spin. in most cases very high friction
values of 90% and higher (friction can go beyond 100%) do look best IMHO.

there are no other options than the bullet solver and the deflection node currently.
  05 May 2013
at the risk of beating a dead horse, here's a better comparison, one in which the dynamics tag is removed, and one with it in place. The very first particle to hit I think is a good one to single out. Just looks more "correct" without the dynamics tag--no bobble, no hesitation on impact--but maybe my brain is just conditioned to think so...

anyhow, thanks very much for your help


Last edited by LML : 05 May 2013 at 05:02 PM.
  05 May 2013
i still do not see it, your animation is just a simple rigid body animation, so the same rules
for as for a static or mograph driven scene do apply.

you can raise the simulation steps in the world settings ctrl+d/Dynamics (or cmd + d). the
freaking particle at the end of your animation is most likely a result of an insufficient
collision margin/ sub step count and a high collision noise value in the rbd-tags (tag/collision/collision noise).
  05 May 2013
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