Timeshift affects chopnet driven motionblur

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So we use a chopnet to cache out animation, since we're dealing with very large amounts of motion blur. Everything goes very well and works good, apart from a timeshift we built into out cache node.

After applying the chopnet animation curves back onto our geometry the motionblur looks good, but when we add a timeshift node (even though we turn integer frames off, or set the frame expression to $FF) the motionblur looks really odd. The only we we can change this, is by changing the method form Frame to Time. This seemed like an option, because we can recalculate the input from the frame parameter to the matching time, but by using a (1/$FPS) the motionblur also gets affected in a bad way.

Does anyone have a solution for this timeshift motionblur problem?

The first image is without a timeshift node, second is with timeshift and set to Frame, third one is with timeshift set to Time.

Kind regards,
Chris
Edited by Klonkel - Feb. 28, 2020 04:51:42

Attachments:
timeshift_motionblur_issue_v001.hip (570.6 KB)
no_timeshift.jpg (140.2 KB)
timeshift_method_by_frame.jpg (139.4 KB)
timeshift_method_by_time.jpg (141.2 KB)

https://www.youtube.com/@Klonkel
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$FF is not precise enough and it can cause issues like you see
So keep your method as Frame but use expression: $T*$FPS+1
Tomas Slancik
CG Supervisor
Framestore, NY
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tamte
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Ah perfect, that works!

Kind regards,
Chris
https://www.youtube.com/@Klonkel
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