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                                                             on Gopher (inofficial)
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       COMMENT PAGE FOR:
   URI   OpenScan Offers 10-Micron 3D Scanning on a Raspberry Pi and HQ Camera Module
   DIR   text version
       
       
        varjag wrote 3 days ago:
        The title is lying about resolution by a couple orders of magnitude.
       
        veritas213 wrote 3 days ago:
        Are there any projects using OEM LIDAR module with pi?
       
        skykooler wrote 3 days ago:
        > The sample scan provided by Megel to demonstrate the scanner's
        capabilities took, he claims, less than an hour of wall time and just
        four clicks of user interaction — though the processing requires the
        in-beta cloud platform or a more powerful host PC, with the Raspberry
        Pi unable to provide enough compute itself.
        
        Is there an actual reason for this? Given the Raspberry Pi is a
        computer too, shouldn't it be able to compute the results as well, only
        slower than a proper PC?
       
          joshvm wrote 3 days ago:
          Photogrammetry is extremely compute-intensive, but it is
          embarassingly parallel. You need to compute feature points in all
          your images (which is generally fairly fast, even if you use
          something like SIFT). Then you have to match features which, in the
          worst case (non sequential images) is a brute-force N^2 problem where
          each N (images) might have several thousand potential keypoints. Once
          you've done that, you do some non-linear optimisation (typically
          Levenberg Marquadt or some variant) to solve for pairwise camera
          parameters, orientations and feature point locations. The joint
          problem is called bundle adjustment and you might have millions of
          points to solve for. Finally you have to mesh all these points
          together using I guess something like Delanuey triangulation.
          
          Even on a good desktop processor, it can take hours for a small
          scene. You really want a GPU for it.
       
          admash wrote 3 days ago:
          The unstated phrase at the end of the sentence being “to finish in
          a reasonable amount of time.”
          
          No one wants to wait two weeks while their r-pi converts a point
          cloud to a mesh.
       
        myself248 wrote 3 days ago:
        So the whole project that I can find documentation for seems to be
        about soldering together a couple stepper drivers (rather than just
        using a scrap 3d printer controller which everyone has sitting around)
        and a ring light, where's the photogrammetry workflow part?
       
          tofof wrote 3 days ago:
          A neat video of the openscan mini in action can be found at [1] and
          the results from that scan along with the cloud processing
          photogrammetry workflow can be seen in the video at [2] The author
          says he wants a one-click solution to getting a 3d model of a scanned
          object. I think that's a great goal - as easy as hitting the green
          button on a photocopier, except now three dimensional. From the
          automated picture-taking and that cloud processing workflow, this
          project is already remarkably close.
          
   URI    [1]: https://www.reddit.com/r/3Dprinting/comments/jx2aww/3d_print...
   URI    [2]: https://www.youtube.com/watch?v=EhvFq-OYa1g
       
          slezyr wrote 3 days ago:
           [1] I think this project is about making a bunch of photos of the
          object and share them with SAMBA. Then you can load them into
          meshroom or another software. It's not all in one package.
          
   URI    [1]: https://raw.githubusercontent.com/OpenScanEu/OpenScan/master...
       
            thomas_OpenScan wrote 3 days ago:
            Yes, this is the current public stage. The device is making a bunch
            of images, creating a zip file that need to be downloaded and
            manually processed. The main advantage already is, that the images
            and the lighting is very consistent, which is major key to
            successful photogrammetry. The upcoming cloud processing would
            further simplify this process, but as I am doing all that alone (+
            help from the community) this is a rather slow progress...
       
            justinclift wrote 3 days ago:
            In that manual, there are several sections.  The first three seem
            to have decent content:
            
            1. Soldering
            
            2. Wiring all parts
            
            3. User Interface
            
            That third one ("User interface") shows how to use the software. 
            From just glancing at it, it seems like it'll be ok.
            
            At the very end there is a list of future things that I'm guessing
            will also be added to the manual:
            
            4. Workflow
            
            5. Build - 3D Printed Version
            
            6. Build - CNC version
            
            7. Photogrammetry Software - Overview
            
            8. Post Processing
            
            Hopefully these last sections are also filled out in the near
            future, as they sound pretty useful. :)
       
        Causality1 wrote 3 days ago:
        What I don't get is why this isn't easy to do with a smartphone. A
        little motorized turntable with a stand for your phone and a
        calibration object covered in tracking symbols to use for adjusting the
        input from the camera. Why is that so impossible?
       
          thomas_OpenScan wrote 3 days ago:
          Actually, this is how I started the project. See for instance this
          one here (OpenScan in 2019 [1] )
          
          But I have found that smartphones give very inconsistent results
          (probably due to image"improving" algorithms...), see [2] So I moved
          on to the raspberry pi + camera, which is much easier and better to
          control as you need very, very consistent images...
          
   URI    [1]: https://www.instagram.com/p/Bt6JtjEoEM7/
   URI    [2]: https://www.instagram.com/p/B1q1syMoHfG/
       
            Causality1 wrote 2 days ago:
            Interesting. What's the materials cost for the pi-based setup?
       
              thomas_OpenScan wrote 2 days ago:
              100-200€ plus the printed parts (~50€).
              But most people diy some or even all parts for even less
       
          yarcob wrote 3 days ago:
          A few years back I tried an iPhone app (123D Catch from Autodesk)
          that allowed creating 3D models just by manually moving the phone
          around an object. No turntable or stand needed.
          
          It worked surprisingly well, but was unfortunately discontinued.
          Since it was cloud based the app no longer works :(
          
          I wonder if there are any similar apps available now?
       
          errantspark wrote 3 days ago:
          It's easy to do with a smartphone and you usually don't even need a
          calibration object. A software like Metashape or Meshroom can infer
          the lens transform and position of the camera from enough photos of
          the same object from different angles. The small smartphone optics
          actually help you by giving you a deeper DoF.
          
          Not the best example but this [1] rock is ~5 cm tall and my best
          guess is the minimum detectable feature size is about 10 microns.
          
          EDIT: Sorry to be clear the definition of easy here is "as easy as
          most photogrammetry", to get good results you will universally do a
          lot of knob twiddling, waiting and cleaning up broken bits of mesh
          unless all you do is scan rocks. Scanning rocks is easy.
          
   URI    [1]: http://koanlabs.org/vignettes.html
       
          mdaniel wrote 3 days ago:
          I don't have expertise in this area, but my  experience with other
          engineering disciplines is that nothing is ever as easy in practice
          as it is in words, because there are a lot of things that can go
          wrong or not be compatible with one another
          
          "The devil is in the details" and "talk is cheap" are common
          expressions for a reason
       
            rrmm wrote 3 days ago:
            Basically, lens imperfections, camera noise, vibration and lack of
            rigid setups (and a hefty dose of etc.).
       
        ohazi wrote 3 days ago:
        That does not look like a 10 micron scan...
        
        Edit:
        
        Here is the source for the claim: [1] It seems this might be the
        theoretical error that you can get when the system can identify a
        feature perfectly, and when it gets a usable reflection from that point
        at enough angles.
        
        But this is not the case for most points on any real object (i.e. not a
        chalk-coated gauge block), so you're definitely not going to get a
        model where the maximum error is 10 microns.
        
        The results are certainly impressive, but hackster.io is taking
        liberties with that headline. It's not a realistic accuracy and the
        author of the project doesn't really seem to be making that claim.
        
   URI  [1]: https://www.reddit.com/r/OpenScan/comments/gfottc/10_micron_ac...
       
          thomas_OpenScan wrote 3 days ago:
          Hi, this is Thomas, the guy behind OpenScan. I really would like to
          clarify several things. 
          - I have never made such a bold claim of 10 micron accuracy for the
          device. Yes, I made several scans, where the accuracy is quite good,
          but I would never say, that this can be reached under all
          circumstances.
          - To be fair, I have been kinda click-baity in the past on a handful
          occasions, but everyone who is doing at least 5mins of research will
          find for instance this one here: [1] - Comparing this 100-200€
          device with an industrial 3d scanner is like comparing a hobbyist 3d
          printer with a highend injection molding machine...
          
          Anyway, feel free to discuss and ask me anything about it :)
          
   URI    [1]: https://en.openscan.eu/quality
       
            ohazi wrote 2 days ago:
            Really nice work, by the way... I hope my comment didn't seem
            overly harsh. I know that doing testing with gauge blocks is part
            of the process and I really only took issue with the hackster.io
            headline.
       
              thomas_OpenScan wrote 2 days ago:
              Thank you and no worries, I absolutely agree with your valid
              criticism.
              Later this year I will get some more CT reference scans to
              compare my results too. I think that this will give some better
              insights.
              By the way, even on the professional market there seems to be no
              „universal“ benchmarking procedure to compare the various
              mid-range scanners (1-20k€). So this is a very interesting
              discussion point
       
          wyldfire wrote 3 days ago:
          I think most 3d imaging stuff uses MTF [1,2] to measure the real
          spatial resolution performance. [1]
          
   URI    [1]: http://www.imagescienceassociates.com/mm5/pubs/What_is_an_MT...
   URI    [2]: https://iopscience.iop.org/article/10.1088/1361-6501/aa9aa0/...
       
          tofof wrote 3 days ago:
          I don't think I follow your reasoning about 'real objects'. Real
          objects can (and usually must) be coated with scanning sprays, like
          the Aesub Blue the author notes in several places that he uses. These
          sprays then vanish completely from the model after a few hours. The
          entire point of these sprays is to ensure that your model is covered
          in features that are perfectly identifiable.
          
          The author makes the 10 micron claim in several other places,
          including [1] about a totally different model. That thread discusses
          ways to quantify accuracy and generally agrees that the rig should
          not be capable of such feats.
          
          But then there are images like [2] in which his scans are picking up
          the silk screening on the surface of the board, which at least lends
          some credence to the idea that he's getting 10 micron accuracy.
          
   URI    [1]: https://www.reddit.com/r/photogrammetry/comments/k5dbtk/auto...
   URI    [2]: https://www.reddit.com/r/OpenScan/comments/ls17tt/closeup_of...
       
            pmiller2 wrote 3 days ago:
            This might be a good place to ask, because I've been wondering
            about this for a while: do any of these scanning sprays react with
            copper, silver, or gold?  I can't ever find an actual ingredients
            list for them, and all the MSDS ever lists is various hydrocarbons,
            which I know won't react.
       
              thomas_OpenScan wrote 3 days ago:
              Cyclododecan has been the industry standard for vanishing 3d
              scanning sprays, but as Cyclododecan is no longer available from
              the textile industry, this kind of spray does not exist anymore.
              Aesub Blue is a rather new product from a young German company. I
              have met the founders last year and they are really professional
              and transparent. Just check out their documentation. 
              To be fair, as the product is so new, possible interactions with
              materials are still not perfectly understood. But from what I
              have seen, the feedback from the professional scanning community
              is very positive.
       
       
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