time warp particles or nParticles?

#1

I have a shot that ramps from 24 fps to slow-mo. I have to simulate some leaves getting kicked up by a passing car. I would like to simulate in 24fps and then apply the time ramp to the cached sim. I’ve seen some threads from a couple years ago saying that nParticles will not interpolate between frames when slowing down a sim. I guess it’s a safe bet that regular Maya particles will not interpolate either? Has there been any good news lately?

I am thinking of running the cached particles through Realflow, since Realflow has a great retiming tool. I can do this effect without changing the particle count anyway, but the RF retime tool has some options for killing particles at the beginning/middle/end of the frame. It is seamless when you have thousands of particles…

As others have noted on here, changing the time scale on the Nucleus node changes the simulation. That makes sense since the acceleration due to gravity has units of meters/second/second. So, I guess all the forces will change when you bend time.

Any solutions to time-warping particles or nParticles? Houdini maybe?

I could maybe even do it in nCloth. Could I then keyframe a ramp in the Trax editor?

#2

Actually, I was able to keyframe the time scale on the nucleus node to match the speed ramp on the camera. It works very well.

Unrelated: I just had a spate of hard hard Maya crashes due to something in the nParticleShape node’s mass scale input ramp roll out. Ugh.

#3

Indeed, setting the “mass scale input” to “randomized ID” crashes Maya in 1/10 of a second after the first particle is emitted. This is Maya 2012 on CentOS. The entire UI evaporates - no hung windows, no suggestion to send a note to Autodesk, it just vanishes.

#4

Hi John

Given the fact that time usually does not change… I’d suggest your best bet is to calculate your slowest fps, do your sim on that and then retime the whole shebang afterwards.

/risto

#5

I can see that there is some wisdom in what you’re saying, but the time scale is working really well, and it’s great for me to be able to playblast and see the speed ramped result right away. Also, it’s nice to be able to just hand off renders that the compositor can slap in without any speed adjustments on their end (or worse, my end! haha!).

#6

You probably already solved it, however if you simulate your leaves with ncloth and cache them you could retime them, blend and cut the cache to your needs with the trax-editor. Unlike the cache of particles it is possible to get the inbetween of cached frames.
Or you could cache/sim your particles with a few more sub frames and retime the cache with the same method(although the cloth might still be smoother when retimed)

Dennis

#7

I tried nCloth but I have a terrible confession. I couldn’t figure out how to timewarp an nCloth cache. When I try to create a timewarp node, I get this:

// Error: file: /software/maya/2012.4.17/linux.centos5.x86_64/scripts/others/getSelectedClips.mel line 65: Operation not valid on cache clips.

Do I need to create a geoCache? That would also be a “cache clip”, though, right? I think I remember trying that and having no luck.

???