Converting rotated STMap to vector appears to scale the image up, and doesn't do the full rotation

[normancates]

I imported this toolset into Nuke 12.2v3.

I created a STMap and transformed it using rotate, and then KeyMixed that onto the original STMap using a roto shape.

Then used STMapToVector2 to get vectors. (I was trying to invert them to see if I could invert the STMap, effectively turning it into a Push distort, rather than a pull distort.)

When I tried inverting the vectors, and converting them back to an STMap, I found that the image in the distorted area was being resized.

So I simplified it all to try to isolate the problem. And I found that the IIDistort node was doing something similar with the image. Even with just the STMapToVector converting to Vectors, and going into the IIDistort.

Then I found that in the IIDistort, if I reduce the Number of Samples to 1, then the scaling goes away, and it looks just like the STMap output. I can understand the distortion around the edges being different, but not in the middle, where it's only doing whatever the Transform node is doing.

This seems like a problem....

[normancates]

Addendum, I also find the VectorRotate tool does the same thing. It's resizing the distorted part of the image...

[herronelou]

Hey Norman. Iidistort works a bit differently than Idistort does. When you set IIdistort to 1 sample it's essentially working the same as Idistort, which should match the output of an stmap when at scale 1. IIdistort divides the scale by the number of samples, then resamples the vectors further, etc.. Vector maps, like stmaps, can't represent rotations at a pixel level, the vectors are a single straight line between 2 coordinates. A 180 rotation would create a vector where each pixel goes to the exact opposite corner of the image through the center. Scaling these vectors (or blending this stmap with a default one) would not result in the image slowly turning, but scaling down to nothing then back up flipped. My guess would be that something like that is happening. If you have some examples you can share I might be able to look into it further.

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On Mon, 21 Jun 2021, 20:03 Norman Cates, ***@***.***> wrote: Addendum, I also find the VectorRotate tool does the same thing. It's resizing the distorted part of the image... — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#31 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAJAV5AZRSMOAJHNPQVAIJLTT3W5RANCNFSM47BASWIQ> .

[normancates]

Erg, I wish I could. But I'm behind a corporate firewall, and getting anything out is a long and arduous exercise.

I'll see if I can get one of the Nuke learning editions or similar on my home machine