Volume Retime Stuttering

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I’ve been struggling to eliminate some stuttering issues in my volume.
Currently, I’m using the retime node and have tried different volume blending Modes, but the problem persists.

Does anyone have any ideas or suggestions on how to fix this?


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One tip is to never have a mix of blended and unblended frames, so make sure your retime coefficient never results in integer frames from the original sequence.
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Tanto
One tip is to never have a mix of blended and unblended frames, so make sure your retime coefficient never results in integer frames from the original sequence.

I have already given that a go in the results above, where the retime frames would never land on frames like 1001, 1002, etc. Unfortunately, that hasn't fixed the problem.
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Your best bet would be to use Advected mode and making sure you have correct vel volume present in your cache

By correct I mean that it represents velocity per second at the current FPS

For example things like simming with timescale other than 1 would produce incompatible vel for retiming ao that would need to be reflected in the settings by scaling it accordingly for advection purposes
Edited by tamte - 2024年12月20日 06:51:03
Tomas Slancik
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Method Studios, NY
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tamte
Your best bet would be to use Advected mode and making sure you have correct vel volume present in your cache

By correct I mean that it represents velocity per second at the current FPS

For example things like simming with timescale other than 1 would produce incompatible vel for retiming ao that would need to be reflected in the settings by scaling it accordingly for advection purposes


By using a timescale on my sim, would there still be a way to get the correct velocity out? Or would there be no other option than to set the timescale to 1?
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You can use a volume wrangle prior to your retime with

v@vel *= chf('timescale');

Then create the spare parameter and link it to the timescale of your sim.
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You can also just adjust the Input Timestep parameter on Retime SOP

Change it to something like
ch("timescale") / $FPS
Tomas Slancik
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Method Studios, NY
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That seems to have done the trick. Thanks!

Is there a reason why the velocity field is not affected by the timescale in the solver? I was expecting it to be?
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Wouter Lichtenbelt
That seems to have done the trick. Thanks!

Is there a reason why the velocity field is not affected by the timescale in the solver? I was expecting it to be?
Because vel is in seconds, timescale affects just advection speed

This makes it much easier for all the velocity shaping tools to work the same way rather than having to account for timescale

Also in real life the velocity of the object doesnt change if you observe it with higher fps camera

It's however important to be aware of this as you may want to adjust vel for the purpose of MB or as in your case retiming
Tomas Slancik
FX Supervisor
Method Studios, NY
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