advice requested for creating 3D model of ancient medieval weapons

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  • William R. Short
    3Dfollower
    • Jul 2022
    • 14

    advice requested for creating 3D model of ancient medieval weapons

    Help and advice is needed, please. I am starting a project to create 3D models of Viking-age weapons using 3df Zephyr Lite, but I am struggling to get a good reconstruction from my photos.

    I am a beginner both with 3D photogrammetry and Zephyr. The object is photographed on a turntable in a light box, so lighting should be good. The camera is a point-and-shoot on full manual mode, mounted on a tripod, and on a shutter delay so there should be no camera shake. I tried both a Android cell phone camera (not as good images) and a fancy mirrorless camera (images about the same).

    I started with some simple objects, such as paperweights with textured, detailed surfaces, and got excellent reconstructions. I tried some replica Viking weapons which I dulled (to avoid reflections from the shiny surfaces) with powder spray, and got very good reconstructions, although the sharp edges of the weapons were never as crisp or detailed as I wished - they looked like moths had been eating the edges, rather than smooth, straight edges.

    I can't do anything to mess with the historical artifacts when I scan them. I can only scan them as is without any sprays or targets attached. I am unable to get good reconstructions with the one artifact I have to work with.

    First, the results are inconsistent. I can run the same set of photos multiple times, with what I believe are the same settings, and the results range from no reconstruction to something that is recognizable. Typically, only a small number of cameras are accepted, and the sparse point cloud is just a jumbled mess with ghost points all throughout the volume, and further processing doesn't help. I use the deep preset from the default menu for reconstruction, and attempts to use advanced reconstruction settings has not helped much. And occasionally, the reconstruction from the same photo set isn't too bad, except for the rough edges.

    Any suggestions on how I can consistently get a good reconstruction? An example set of photos of a spearhead is here in a zip file:

    and the best reconstruction from that set is here (most of the time, the reconstruction failed from this set):

    Many thanks.
  • cam3d
    3Dflover
    • Sep 2017
    • 662

    #2
    Hi William R. Short

    Welcome to the forum! Thanks for sharing your .ZEP and images, very helpful! Here's my feedback:


    - Use general default settings when orienting cameras in the first stage of processing. Using higher settings can over compensate and find false positives which drive the reconstruction off course.

    - Use mask by colour to speed up your masking process and get better silhouettes: https://www.3dflow.net/technology/do...for-turntable/

    - Your camera settings look OK but some of your images have very soft focus - This is either because your using auto-focus or the lens itself is just a bit soft. I think a bit of both. You can use a DOF calculator to precisely tune your manual focus so that the subject is always in the correct range. https://www.photopills.com/calculators/dof

    - Your camera is 16mpx and the optics/sensor are OK but could be much better. For commercial applications I use 42mpx Sony A7R4 and high quality optics (20/55/90mm dependent on subject) the better your images, the better your results.

    - For sharp edges sometimes a LOT of images are required, especially with a lower resolution sensor - Image count depends on many other factors and needs to be felt out on a case by case - The more you scan the better you will be at estimating required count :-)

    Hope these tips help!

    Last edited by cam3d; 2022-07-07, 03:18 AM.

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    • William R. Short
      3Dfollower
      • Jul 2022
      • 14

      #3
      Originally posted by cam3d

      Hope these tips help!
      Yes - they give me valuable ideas about what direction to take to improve the scans. I am grateful.

      Comment

      • Ivkolya
        Blossoming 3Dflower
        • Jul 2022
        • 2

        #4
        If you struggle with reflections from metal parts - try to play with cross-polarization. What I did was to buy circular polarization filter for the camera lens (I've bought a cheap used CITIWIDE CPL 58 mm for around $5) and put a piece of polarization foil in front of the light source (I've bought a sheet of polarization foil for $7 from a guy, who repairs smartphones).
        Even without external flash, with just a small piece of the foil duct taped to the built-in flash of the camera (I used Canon EOS 750D) the results are very impressive.
        Here are test photos with direct flash (shot from ~30 cm) without and with cross-polarization. Click image for larger version  Name:	Screenshot_1.jpg Views:	0 Size:	166.0 KB ID:	8319Click image for larger version  Name:	Screenshot_13.jpg Views:	0 Size:	334.6 KB ID:	8320
        Hope that helps.
        Last edited by Ivkolya; 2022-07-28, 05:26 PM.

        Comment

        • cam3d
          3Dflover
          • Sep 2017
          • 662

          #5
          Nice! - You can also use polarizing filters on the light source for cross polarization :-) https://petapixel.com/2021/01/19/cro...hy-it-matters/

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