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Best workflow for timeshifting cached RBD sim


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Hi all,

I have a RBD simulation that I want to timeshift and I'm wondering what would be the best way to do this.

Is there a way I can cache my sim and apply the timeshift after to get more interactivity? At the moment, when I do this, it does interpolate in between frames. I saw a thread talking about a mix of timeblend and timeshift, but I can't understand how to use them together to make the desire effect.

I've been able to make my timeshift work when the simulation isn't cached, but this workflow is too slow to be usable...


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Hi, I know how you feel. For simple little tests, timeshifting the live simulation works fine. but for more complex simulations, that workflow just doesn't really cut it.

I usually will use the timeshift sop with my cache to get the 'slowmotion' look right. not worrying about the stepping between frames. You can still get things animated with it, and it's relatively quick.

Since the timeshift sop cooks it's input accordingly, feeding it a cache obviously doesnt yield good results. So use it after the dopimport sop, and by using 'explicit cache' on the dop net, and caching substep data, the timeshift sop seems to only cook what it doesnt already have from the explicit cache.

you may have to constantly reset the dopnet, to clear it's own cache, in order to let the timeshift sop cook the "new frames".

Hope that makes sense, or helps at all!


edit: otherwise, depending on your sim I suppose. you could use chops to extract the transforms, and export the channel data back into the rbd's. Since you'd now have interpolated f-curves, retiming would be a snap. But, you may run into some nasty gimbal lock, and it may not be that accurate, since everything is interpolated from the original motion. I dunno.

Edited by Garbanzo
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Hey Garbanzo,

At the moment, I'm running a lowrez sim with explicit cache as you mention to make my timeshift and when it will be set correctly, I will simulate with my hirez sim.

I'm not so confident with chop, so I'll stick to SOP and DOP :). Still a lot to learn :)

Thanks for your input!


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If you want a perfect sim go for a higher FPS. Let's say you want to slow down a simulation by 4 times. If the projects simulation is 25fps simulate it in 100fps and then retime afterwards. If you want to turn down the vel based on the timeshift it is possible see the hip (in case you don't want things superblurred while they are going in slow motion).

I hope the file helps. I created some notes. For the vel I basicly compare the derivate of the timeshift curve to the underlying simulation's FPS and mult the vel. 8in other words compare the motions FPS with the cached sim's FPS)

Maybe this won't help if you only have a cached sim. Otherwise sim it again with higher FPS :)

Good luck!


Edited by Hudson
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Hey hudson,

Thanks for sharing the hip, I'll take a look at the office later.

Yesterday, before going back home, I realize that I have a gimble problem at a precise frame in the sim when I timeshift. It' an important slowdown that i'm doing, like a keyframe at 20 with frame 20 and a keyframe at 100 with frame 23. It's a big slowdown. I'll try to sim with a higher FPS, maybe it will help.

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If your time shifting the live simulation, there shouldn't be any gimbal issues. Gimbal locks lives in the middle axis of an Euler rotation order.

That's quite the slow down, stretching 3 frames into 100. You would have to have a ridiculous fps to support that, if that's the route your trying to take.

I would still try time shifting the live sim, so at least the time shift cooks what it needs, instead of just simming extra frames.

Or maybe, instead of trying to retime the slow parts, run your sim at the slow speed, and retime the normal/fast moving parts. That way, you'd be dropping frames, instead of trying to add/interpolate new ones. I guess it's all situational.

If only you could key the timescale on the dopnet, lol.

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I timeshifted it with the live sim and it's working really well. That wasn't a Gimbal problem, it was a shift on one frame in the viewport specular that gave this impression or gimbal lock. I created flipbook in hidden line and everything worked correctly.

Thanks guys for the help.

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