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I had to deal with this a year or so ago. You're right, the
particle orientatin will flip. You're also right about orientation being a
problem with deformed particles.
My solution was to build a scripted op onto the particles
that did the orientation properly, using an up vector. It wasn't that hard, but
then it's only not hard if you have the relevant skills.
K.
From: owner-xsi(at)Softimage.COM
[mailto:owner-xsi(at)Softimage.COM] On Behalf Of Morten
Bartholdy
Sent: 30-March-2006 14:38
To:
XSI(at)Softimage.COM
Subject: Re: How to control Particle instance
orientation?
Hi Eric,
I suppose you mean deforming the cloud to get a
swimming school of fish rather than use goals!? I guess it is worth a try, I
just see a problem with particle orientation when the particlecloud is
deformed. I don't recall if there is a script somewhere to fix
that.
Morten
----- Original Message -----
Sent: Thursday, March 30, 2006 3:00
PM
Subject: Re: How to control Particle
instance orientation?
Morton,
Have you tried deforming your cloud with a cage deformer or a lattice
instead of directly on a curve?
I usually use a lattice deformed on a curve, it appears less
rigid. Also you can get a lot of nice secondary anmation by
attaching a slow shape jitter or a wave or even animated cluster
centers on point along the curve. I am not sure what this will do to
the up vectors, but I suspect it might handle it differently. Worth a
try.
Eric
Freelance 3-D Animator, F/X Artist
----- Original Message ---- From: Morten Bartholdy
<xsi(at)colorshopvfx.dk> To: XSI(at)Softimage.COM Sent: Thursday,
March 30, 2006 3:17:19 AM Subject: Re: How to control Particle instance
orientation?
Hi Mathieu,
Yes the roll provides active control - actually
if I for instance leave the roll at 90, which should make the fish
swim on their side, they flip for every turn in the goals path, which makes
me think there is some upvector control in play under the hood.
In my test scene I have the goal following a
path which is roughly shaped like an S. For every turn the particles bank or
roll and I have yet to find a way to avoid or control that precisely.
Actually it seems the amount of roll is not the same for every turn. The
trouble is that if I try controlling it by keyframing the Rotation Velocity
Roll, the fish in the front rolls before the one in the back of the school,
which is why I'd rather find a sort of upvector contraint.
You can see the problem in this
movie:
Notice how the particles are actually being
orientated with something like an upvector constraint as the goal takes
effect shortly after emission, and at the right turn they roll almost on
their side. This is directly influenced by the sharpness of the turn on the
path, a bit like the orientation problems when extruding a curveprofile on a
curve.
Any hellp is much appreciated.
Morten Bartholdy
3D & VFX
Artist
----- Original Message -----
Sent: Wednesday, March 29, 2006 5:30
PM
Subject: RE: How to control Particle
instance orientation?
Doesnt
the roll parameter from the Rotation Velocity control that? Maybe Im
misinterpreting your question but seem to me thats the control to play
with. The other way would be to create a scripted particle event and
control the orientation from a script. Im not sure if Im being very
helpful here so feel free to elaborate a bit more on the problem if you
want more help.
Mathieu
Leclaire
R&D
Programmer
Hybride
Technologies
-----Original
Message-----
From:
owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM]On Behalf Of Morten
Bartholdy
Sent:
Wednesday, March 29, 2006 2:35 AM
To: XSI(at)Softimage.COM
Subject: How to control Particle
instance orientation?
Hi
all,
I
am creating a school of fish using of instances on particles
following a goal, and it is sort of working alright. Problem is to control
the upvector of the instances - the fish roll on their path when the
goal changes direction. I have Align on velocity on and this is working
fine, the instances direction use rotation, and face direction use
rotation which I am not quite sure has an effect on the instances, but
apart from plotting and controlling the upvector directly, is there
something for controlling the roll I have missed?
Morten
Bartholdy
3D & VFX Artist
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