Texture Re-Projection in Mari/Nuke

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    Wishgranter
    Hi Joseph Steel

    For the undistortion parameters:

    1. best if you use INNER region fit -> look at the attachment which describes the regions fits

    2. Resolution -> PRESERVE

    3. I would recommend you to use FALSE

    Is there a more in-depth NUKE + MARI camera description so that we could understand the SCALE and other parameters used for proper camera export?
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    Joseph Steel
    Hi Milos,

    Thank you for the quick reply, that image makes perfect sense. I just ran your settings. I still have to scale the images down to get them to match. Please see details below:

    Values in RC:
    Screen Shot 2016-03-29 at 13.47.01.jpg


    Camera data in Mari with principle point translation (this works):
    Screen Shot 2016-03-29 at 13.47.09.jpg


    FOV is calculated using the horizontal aperture and the focal legth ( 2 * atan(hap / (2 * focal)) * 180 / pi ):
    Screen Shot 2016-03-29 at 13.47.18.jpg


    Mari doesn't show the camera details, so here is the same camera in Nuke:
    Screen Shot 2016-03-29 at 13.47.38.png


    To get the images to lock I have to scale the image down by 0.03.

    The other main issue; is the bit depth and colour space. When exporting undistorted image they are reduced to 8bpc SRGB. Is there a button to retain colour space + Bit depth?

    Cheers,

    Joe.
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    admin
    Hi Joseph,

    We had the same issue with Maya export, which was observed after adding image plane. We've add image plane to Maya export too. It will come with the next update (or attached).

    In general, the "scaling issue" is due to the film gate size and versions of that. For Maya we are exporting it with the fix to avoid default parameters fighting.

    For mari/nuke I would recommend using un-distorted images since lens distortion is always present and it always causes some image deformation. To avoid wasting of pixels we have support several modes for image un-distortion. Since cropping may happen the focal length is changes. But values exported with xml/maya/whatever output are always compensated. If mari/nuke supports some ascii scene format, then it should be very easy to write custom export for it. Check "calibration.xml" file in the application folder. It defines how to export registered cameras and you can make your own export easily.

    Here is some topic on that - Camera export and file formats
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    Joseph Steel
    Solution for this problem is posted here Camera Projection matching
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