Shapeways' rendering of an uploaded part does not match my design

Discussion in 'Bug Reporting' started by Hobbes010, Dec 16, 2013.

  1. Hobbes010
    Hobbes010 Active Member
    I'm working on some small parts, and I noticed a difference between what the part looked like in my CAD application/Netfabb, and the rendering that was generated when I uploaded the part.
    'Part in Netfabb' shows what I've designed. The surface is smooth:
    part in Netfabb.jpg

    'Shapeways import' is a screenshot of the product upload page. Note the rough surface:
    shapeways import.jpg

    Initially I thought it might be a problem with the STL export from Netfabb, but when I re-import the STL into Netfabb it still looks smooth. Same when I import the STL in Meshlab.

    Stranger still, I've uploaded several versions of this part. Some are rendered smooth, others are rough, but I haven't changed any settings between uploads.

    The uploaded part is here
    I've attached the STL.

    Attached Files:

  2. stonysmith
    stonysmith Well-Known Member Moderator
    That is caused by the underlying technology in the new renderer.
    As good/fast as the new renderer is, it will always have this "problem".

    The new renderer uses "Voxels" instead of "Triangles" when building the image, and the image it builds is a bit lower resolution than your actual model is.

    The full-resolution model will be sent to the printer, and you (should) not see such artifacts in the final print.
  3. Hobbes010
    Hobbes010 Active Member
    Ah, I see. I was worried that my STL was being converted after the upload, but if it's a display issue only I can live with it.
  4. AlanHudson
    AlanHudson Shapeways Employee Dev Team
    where is this screenshot from, the wallthickness visualization or the thumbnail? The wallthickness viz is voxelized. Your model is not and so the thumbnail we render should not show those artifacts.
  5. Hobbes010
    Hobbes010 Active Member
    The screenshot is from the rotatable/zoomable model on the 'Edit Model' page.
  6. MitchellJetten
    MitchellJetten Shapeways Employee CS Team
    Alan, we didn't launch the wallthickness visualization yet ;)
  7. AmLachDesigns
    AmLachDesigns Well-Known Member
    But it's good...

    I believe stony is correct, that the 'Edit Model' voxel issue (whatever they are!) is the cause. I would be very surprised if the yet to be released wall thickness visualisation image and the 'Edit Model' view were not based on the same tech.

    My experience is that the boring old shop renders (static and 3d) give pretty good indications of what will be printed. Of course you have to take into account the size of the model and the resolution of the printer, but that being said, these images work for me.
  8. MitchellJetten
    MitchellJetten Shapeways Employee CS Team
    Yes it is :)
    Last edited: Dec 17, 2013
  9. stonysmith
    stonysmith Well-Known Member Moderator
    @Hobbes010: One unrelated question: what browser are you using? I seem to be unable to zoom in that close to my models when using that 3d viewer.
  10. AmLachDesigns
    AmLachDesigns Well-Known Member
    For myself, I use Chrome and I can zoom in super-close.
  11. Hobbes010
    Hobbes010 Active Member
    I'm using Firefox. Zooming only works on the 'Edit Model' page. If you're on the shop page, you can't zoom.
  12. wedge
    wedge New Member
    That are Lighting artifacts.
    Normally the most renderes smooth the surface using interpolate normals.
    Shapeways rederer do this not. This has a reason:
    If the rederer would smooth the round objects, the costumer do not see on the preview, what he really gets.
    The rendering looks smooth but the object is very lowpoly and faceted.
    This problem you have is has other models to.
    Yo can see it on the knob. Your model is extreme. It do not affect the printing it just looks ugly.
    At the moment i have tot full understand witch causes the problem or how to avoid it. :(
  13. Hobbes010
    Hobbes010 Active Member
    I would be very much surprised if Netfabb did this. The model as shown in Netfabb matches my design exactly, there are no extra surfaces compared to my original CAD model.
    A low-resolution rendering would explain the difference, basically you get rounding errors in the position of each pixel.
  14. stannum
    stannum Well-Known Member
    That's a remeshing of the original mesh, not just lighting artifacts. He shows a different face layout in the green renders, with lighting artifacts that don't match the grey ones.
  15. wedge
    wedge New Member
    ? There is not realy a face layout in the green redering visible.
    If I download the STL an view the mesh I find the characteristics of the mesh in both images.

    anyway the conclusion is, these are ugly artifacts an not affecting the print.