Is There A Way To Bake Cloth To Move In Slow Motion?

The project I am working on will have some slow motion shots
that I am hoping to do without cutting back and forth between
fast to a slowmo clips. If possible I want a seemless smooth
transistion all in the same animation.
I can easily move the keyframes around to make the characters
go from fast to slowmo, but they have cloth sim on certain
parts and it would look goofy if the cloth was still jiggling at normal

Is there a way to slow things down?

I thought about using low gravity, but I think it will still move
fast. I’ll figure something out to make it work, but if anyone
knows of a more set way of doing this it would save me a
lot of time.


Changing gravity does work pretty well. I just tried it.

I think I will first key the animation from start to finish.
But bake the normal part.
Render that section.
Then take the last frame of the from the cache fold.
Set it anywhere else it won’t be re-written over with a new bake.
Set the frame numbers where slowmotion starts to happen.
Rebake, then replace the that first cache file with
the one that was set aside, rebake again with low gravity.
Since the frist frame of cache was the last from from the
normal speed, it will calculate everything moving slower,
but starting from the right shape/position so it has a smooth

It’s a little tedious, but I think it will work. I just tried it
and it seemed to do the trick. Only problem is it only
worked the first try. The other tries it ignored the
the cache file. I think there may be a sepcific order
this has to be done in for it to happen. I didn’t keep
track of it the first time. I’ll figure it out and post it here.

Maybe I have to change the gravity setting first, then
replace the cache frame, then rebake.

You might be able to do this in the Sequence Editor. Try if you can add the speed plugin to the strip and see if you can manipulate the speed ipo of the strip. I haven’t tried with transitions but speed up and slow down without transition work like a charm with the speed plugin.

It’s a lot of work but for true slomo (stretching time rather than futzing with the gravity) you could convert the sim data to shapekeys for your cloth mesh then space the keys out according to your time dilation. This would give you absolute control over the timing, but you would have to have a completely acceptable bake first.

I have a procedure for converting Cloth sim bakes to shapekeys if you are interested.

Dude! That’s a freakin good idea. Shape keys. It never crossed my mind.

This might work for certain situations, but I don’t want to stretch the video
frames out. Unless I missunderstand the speed plugin. I’ve never tried
using it before. But I have done a lot of video editing. The only way this
would work is if this plugin does not need an already rendered video clip,
but rather it controles the overal speed for the timeline, so when I render
the animation, it would be rendering more frames to fill in the gaps for
slow motion. The look I’m going for is smooth motion rather than what
video editors do when you stretch a clip.

Thanks though musk. I wasn’t aware of the speed plugin so that sould
be fun to mess with in the future.

Yeah the speedplugin works on rendered out images so you will have to have enough frames as you stretch them out or else you are going to see artefacts.
My idea was more along the line do the cloth simulation on the slowmo framerate and then speed up the parts that you want to go normal. That way the speedplugin drops out frames but doesn’t stretch them.

Unfortunately the cloth sim doesn’t play well with effects like slomo, it’s geared to do a physics sim at an assumed frame rate of 30fps and everything else is pretty much ignored. So you can’t do “extra frames” across a time-stretched action, the cloth will act “realtime” regardless.

@Ghost_Train – I thought up the Cloth sim -> shapekeys trick as a way to get around the totally crappy bakes I was getting, but it should work for slowing the motion as well. In my experience (see the last part of the Kata thread in my sig below) I could use a 5-frame gap between keys, with a few places where the motion required fining that down to 2 or 3 frames, and not have any undue effects, so potentially you could slow your motion by a factor of at least 3 or 4 by making every sim frame into a shapekey and setting the keyframes with a 3 to 4 frame gap.Maybe more if your cloth motion isn’t too complex.

But for long sequences that means a lot of shapekeys! So beware, that way madness lies :wink: