Enblend HDR/merging artefact

  • Pierre

    Pierre - 2008-09-29


    Now Enblend can use HDR/EXR input output I have done some tests. And I have observed on some project that I got strange color artifacts.

    Those artifacts are characterized by violet flecks or black holes.

    See the attached files :
    -    Fleck.jpg (tone map version to show you the artifact localization)
    -    Fleck.hdr the Enblend Result.

    You could find my test files on the following address : hhttp://francemapping.free.fr/enblend/Enblend_fleck_sample.zip

    Do you have some ideas from where the bugs could come ?

    If you some ideas, I can test them on the Enblend Code source with you.

    The problem is only observable on HDR scenes.
    (i.e. if you tonemap the input files and launch Enblend on it, you will not got those Holes and Artefact anymore).


    • Brent Townshend

      Brent Townshend - 2008-09-29

      I have seen the same thing in several panoramas before.   I tracked down the problem last year and I believe it is due to the occurrence of negative values in the output of nona as reported in the bug report:



      • Pierre

        Pierre - 2008-09-30

        The black observed holes don't have negative value but values with a perfect 0.0 value.

        I think the problem come from value near 0 as said in the tracker you have send.

        So could it be a precision problem ?

        Or the laplacian blending code put in default when working with floatting point data ?

        It could be interesting if we investigating more and find a fix. Because I have this black holes problem on many scenes and the render is totally unusable.

        Best Regards,

    • David Brodsky

      David Brodsky - 2008-10-08

      Hi, I've got similar problem. I'm unable to make hi-res hdr panorama with enblend/enfuse. I use hugin so I'll describe this toolchain.

      First method:
      nona -> make hdr stacks with hugin_hdrmerge -> enblend to make panorama
      The result can be seen at http://trekie.sinister.cz/enblend.jpg - red areas represents pixels that have NaN in red channel, other channels are ok.
      hugin_hdrmerge makes OpenEXR format, I've tried to convert hdr stack into tiff with enblend and then use this again to make the panorama and the result is the same. Output format from final enblend step is OpenEXR (I need this one).

      Second method:
      nona -> make ldr panorama with enblend -> use enfuse to make hdr panorama
      Again, the result can be seen at http://trekie.sinister.cz/enfuse.jpg - I wouldn't mind white/yellow/red colors around the picture (where actually is nothing), but wrong colors are located in the tree on the left and also cathedral suffers from this.
      This time I've converted tiff output from enblend into netpbm format and then to OpenEXR (so this is the input for enfuse) and enfuse's output format is also OpenEXR.

      Personally I'd like to use the first method and it also looks that I could debug enblend more easier than enfuse, because I have small input images (located at http://trekie.sinister.cz/redblend.zip\). Does anyone know if I do anything wrong or where should I start? Enblend and enfuse are so far the only programs for Linux I know that can handle very big pictures.



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