Thanks for the tips and example Andy (& everyone). I'll work on implementing this into my approach.
On Mon, Jun 4, 2012 at 1:32 PM, Jonathan Laborde <[email protected]>wrote: > I made 2 compounds that I use regularly to calculate velocity properly. > You basically store the current point position and orientation at the > beginning of every frame (first port in the stack). Even if you are say on > frame 10, since it's the first thing being calculated in the stack the > point position is still from frame 9. Then in post-simulation you do the > actual calculation and store it in pointvelocity and angularvelocity, that > way it won't affect the following frames. > It works well, unless you are moving the points in post-simulation as they > won't be calculated at the beginning of the next frame. > Enjoy! > --* > **JONATHAN LABORDE* > FX Artist > > www.rodeofx.com > > > On Mon, Jun 4, 2012 at 12:25 PM, Grahame Fuller < > [email protected]> wrote: > >> Verlet integration might be useful in these cases. With Verlet >> integration, you store the previous positions and back-calculate the >> velocity from that, instead of calculating the forward velocity as in >> standard Euler integration. >> >> gray >> >> From: [email protected] [mailto: >> [email protected]] On Behalf Of Andy Moorer >> Sent: Sunday, June 03, 2012 02:18 PM >> To: [email protected] >> Cc: [email protected] >> Subject: Re: ICE: Vortex and Lagoa >> >> Yeah I should have pointed that out... There's always a sacrifice between >> the simplicity and emergent behavior of simulations and the control you can >> get by being more direct and specifying explicit positions per frame. >> >> The more "custom" you get, the more you have to chase down and account >> for this kind of thing. The motionblur problem with nonsimulated ICE >> animations is the biggie - enough so that it might be advisable for the >> softimage devs to implement some in-box solutions, like perhaps an option >> for computing a per point velocity during caching, or writing special >> "absolute" point position and velocity variables after the post-process >> step... >> >> >> On Jun 3, 2012, at 1:36 PM, Jonathan Laborde <[email protected] >> <mailto:[email protected]>> wrote: >> Great answer Andy. But be careful with such a technique (blend between >> simulation and manual positioning) as the point position will be as you >> expect but point velocity will not be calculated properly. Your motion blur >> will be wrong in that case, and you will have tu manually set it in post >> process. >> Rock n' roll >> -- >> JONATHAN LABORDE >> FX Artist >> >> www.rodeofx.com<http://www.rodeofx.com/> >> >> On Sun, Jun 3, 2012 at 11:33 AM, Andy Moorer <[email protected] >> <mailto:[email protected]>> wrote: >> Byron hi there. Can't answer your questions about differences between >> lagoa and "normal" reaction to forces, but the results you are seeing with >> a combination of forces (one to move particles along a curve, the other to >> draw particles towards a curve) is one I'm familiar with. It's easy to fall >> into the "simulation trap," where you drive yourself crazy trying to find a >> perfect balance of forces to get the results you want. >> >> There are a couple of suggestions I can give you... The first is to clamp >> the maximum speed at which a particle is allowed to move: get particle >> velocity, get "length" or magnitude of the vector (this is "speed.") If the >> speed > a max value you set, new speed=max value. Normalize your original >> velocity vector and multiply it by new-speed. >> >> The result, particles obey the forces you set, but never travel so fast >> that they get flung away, and never develop enough momentum to get out of >> control. A drag force coupled with velocity can produce similar results . >> >> Another option is to replace or blend your "suction" and "along curve" >> forces with a setup which places each particle at a specific position in >> relation to the curve, animated of course. I haven't tried this kind of >> approach in this particular context, but in general the result is a hybrid >> of a simulated look and an "absolute" look... particles are simulated to a >> certain extent, blending to an absolute predetermined position. I've >> attached a simple example of this kind of thing, a simple post-sim blend >> between a simulation and goal positions on geometry. >> >> Cheers >> Andy >> >> On Fri, Jun 1, 2012 at 9:32 AM, Byron Nash <[email protected]<mailto: >> [email protected]>> wrote: >> I'm trying to make something along the lines of this video from Firebird >> https://vimeo.com/29367269. It uses Lagoa and some of the vortex >> techniques Brad showed in one of his videos. I can get it to move somewhat >> but can't keep the points on the curve. They tend to fling off despite >> increasing the "suction" controls. How does Lagoa respond differently to >> forces than normal ICE particles? >> >> >> >
