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I bumpt into a STMap artifacts problem

In Nuke i generate a plate

red (x+0.5)/width green (y+0.5)/height" blue 0 alpha 1 STMap undistorted

Format is EXR 32bit zip1

In Blender I undistort it with the tracking result and render it out as an EXR 32bit zip1 Blender undistort STMap generation

When I use this STMap for lens distortion in Nuke then i get artifacts top artifacts, lower clean render from blender

The lower and clean part of the image is the lens distortion applied directly in Blender.

Artifacts only appear when i render a EXR. Tiff does not have that problem, but does not allow linear workflow nor is it 32bit.

Something I found in an other Forum: https://www.mail-archive.com/nuke-users@support.thefoundry.co.uk/msg12365.html Quote from this thread: ¨Just to follow up. I spoke with the folks at Imagineer and they said the issues with distortion maps were fixed in v4, but it's possible that exr's are still affected. Tiff's are being rendered correctly from Mocha Pro v4 at 32-bit and the aliasing problem has disappeared.¨

What I'm doing wrong. Is there a faulty implementation of the EXR code?

Thank you for your help.

Differencemap Tiff vs. EXR: Difference Tiff vs. EXR - should be black

This image heavy gamma lifted to show the differences in the picture. Ideally if everything works as expected with EXR the image should be black (RGB 0,0,0).

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  • $\begingroup$ Although I am completely unfamiliar with your particular software and issue, could you explain what the exact error you are seeing is? Is it the shearing across the image? Part of the issue would be properly decoding the JPEG, and linearizing the nonlinear encoding. Hard to know exactly where the potential breakage is, as there are many points that could snap. $\endgroup$ – troy_s Oct 24 '19 at 3:27
  • $\begingroup$ Hi Troy The last picture with the car shows it clearly. The upper part is blocky or shows artifacts, the lower part of the picture is how it should look. This gives you an overview: vfx-rants.blogspot.com/2013/07/… $\endgroup$ – michael Oct 24 '19 at 11:39
  • $\begingroup$ Guessing you are ingesting an EXR? Regardless, are you flagging the image buffer as non-color data? $\endgroup$ – troy_s Oct 25 '19 at 6:22
  • $\begingroup$ Unfortunately, there is no such option (non-color data) in Blender when you load a single image to the compositor. I'm not going through the Shader Editor. This workflow is not limited to lens distortion: it can also be applied to bend and warp objects in compositing that are behind a rendered (CG) transparent object (IOR). How can I provide more help? pm? $\endgroup$ – michael Oct 25 '19 at 6:53
  • $\begingroup$ Open image editor, properties. You set the colourspace there. It’s dumb, yes. $\endgroup$ – troy_s Oct 25 '19 at 14:29

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