Thanks for the info Peter. Upon further
investigation I think my problem lies int the fact that RBD seems to work poorly
with actual shape vs. much better with convex hull. With actual shape I have to
freeze transformations putting each wall piece center in the world centre, which
makes subsequent plotting useless. If I dont do this my wall pieces fall through
each other and start simulating from somewhere inside my wall breaking passive
rigid body, which provides a useless sim. In a simple scene I can get everything
to work nicely with simple rectangular bricks and convex hull, and even collide
and react to changes in RBD settings in predictable manners. Not quite so
with actual shape. I am afraid I will have to rebuild my collision objects so
they will work with convex hull and fix the inaccuracies by hand -
damn!
----- Original Message -----
Sent: Tuesday, June 26, 2007 7:14
PM
Subject: Re: A couple of RBD
questions
Im pretty sure I've done just this, replacing
simulated RBD's with nulls, getting the animation as transforms to the nulls,
and then parenting the highres geometry under the nulls, and it was on a few
thousand, without any scripting and it didnt take all that long.
I'd recommend trying a scene with just 2 or 3
objects to try out what is the right order of doing things. I remember it
being a bit quirky, and needing a few attempts to get it working.
I think you have to go to the beginning of your
simulation, turn caching on and then run the simulation.
when you're at the end you can scroll
through the timeline at will, proving that it does pick up the caches
allright. Once you have those you can plot the transforms, and
from there its whatever way suits you to
get those fcurves onto the objects you want.
I dont recall if I constrained nulls to the rbd's
and plotted those, or if I plotted the rbds themselves and copied fcurves
across. But I think but worked, once you have the caches, and no
sooner.
----- Original Message -----
Sent: Tuesday, June 26, 2007 3:05
PM
Subject: A couple of RBD
questions
I am breaking a wall with RBD and am using a
set of pieces which are slightly smaller then the ones I want to render so I
can avoid interpenetration in the beginnnig of the simulation. Now I
know I can transfer the cache to a clip in the mixer, but if I want to
copy this motion to each renderpiece or constrain these to the RBD'ed pieces
it starts looking a bit complicated. If I create a cluster with center my
RBD is shot. Next thing I would try is to multi point constrain my
renderpiece to the RBD piece but this requires me to create three clusters
on each RBD piece and then three point constrain each renderpiece to those.
Please tell me Softimage thought of easier ways to handle something like
this with up towards 100 separate RBD pieces???
Another thing is my pieces tend to explode a
bit away from each other even though I have made absolutely sure there are
no interpenetrations at the bewginning of the sim. I have increased
simulation and collision acuracy to very high levels without quite getting
rid of this behaviour. Also I have elasticity all the way down to 0.001
since these are supposed to look like concrete pieces, but I still get weird
styrofoam like bounce and sploinng-like fly away behaviour from the odd
piece when it collides with something again after landing on the ground. I
have tried messing with friction parameters without much luck.
I am guessing there a tips and tricks I still
need to learn about the wonderful world of RBD'ing so if someone knows a way
to dampen simulation collisions I would be happy to hear them, if someone in
the know cares to share some insight.
Thanks!
Morten Bartholdy
3D & VFX
Artist
