Motion vector cache with ROI

I’m currently working in 2022.3 on Linux and I’m doing a lot of warping / tracking with motion vectors generated and cached inside action.

Can anyone confirm if they’ve successfully used the region of interest function to limit the area of frame considered for analysis?

I’ve been consistently getting some crazy results when I turn it on. Almost as if the vector values have been scaled up before being applied to the surface being warped. So when an object in the analysed plate moves around the frame, the warped surface pixels move 2 or 3 times further than they should.

My work_around has been to crop the plate with a resize node before feeding it into action, doing the work and then resizing back to native res before comping. Which is fine, I’m just interested to know if anyone else is experiencing this.

Full res vectors work as expected, but on long sequences they’re burning up framestore space pretty quickly.

One last question. The cached motion vectors have clip history turned on despite disabling that feature in preferences. They also have maybe 15 versions accessible from the timeline. I’ve searched the flame documentation but can’t find any reference to this behaviour. Any info would be much appreciated.


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many aspects of MotionVector tracking are really flawed.


Welcome to the forums! I use motion vectors pretty much every day, and my standard workflow is to crop the image down to the smallest possible size before analyzing MVs. As far as history/multiple versions of cached MVs, I do my best to just keep the most recent or ones that I’m using. As of now it’s a manual process.

Are you doing this in Batch Groups or in BFX?



Hi Andy,

Thanks for the reply, I’m using batch groups.

When I say multiple versions I don’t mean multiple clips, I mean in the timeline sense of “version”. So if I reveal the motion vector cache in my library and then view it’s timeline, I can click on the “versions” button and see 15 occurances with the same name in a list.

I noticed that the same clip in the library has an “H” icon on it, but when I go to view it’s history I get a message telling me it’s not possible to edit motion or ml history.

I wanted to see if I could disable either of these to save a bit of space. I’m fairly new to this motion warp business so just trying to understand what’s happening a bit better!

Totally! I think what you’re seeing there is actually the motion vectors being encoded as a multichannel clip as opposed to multiple versions. But I could be wrong.


I’m not on the box at the moment but I’ll take another look after the weekend.

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