Oversmoothed model previews?

Discussion in 'Customer Service' started by crisrose, Aug 6, 2008.

  1. crisrose
    crisrose New Member
    Hi there,

    So i've been working for a long time to get the perfect level of detail vs filesize, but have had some problems with flipped normals and the like.

    Anyways, i have seemingly fixed them, as my 50k faces models now upload and i'm happy to order them.

    However, the model preview now seems to be seriously oversmoothed?!

    The new scaling options on upload are great, and the fact that it zooms right into the model in the preview is also excellent, well done chaps!

    But the model in Accutrans now is very dissimilar to the previews of the uploaded models.

    Can you confirm that the preview is no longer an accurate representation of the actual printed model? I don't want to get it printed and get what's been shown in the preview!

    Attached is an example.

    Cheers :)

    Attached Files:

  2. crisrose
    crisrose New Member
    Here's another example to demonstrate that it isn't an issue with the model.


    Attached Files:

  3. Dalhimar
    Dalhimar New Member
    It is possible that this is being caused by the format you are using to upload. Some formats will convert the models from a "Mesh" type to a Nurbs/spline type. When this happens it tends to remove sharp edges and some detail in place of not having to store as much information regarding the placement of each individual vertex. Try uploading as another of the supported formats.
  4. crisrose
    crisrose New Member
    Thanks for the input!

    But i think you missed the crux of my point:

    The format hasn't changed, the model hasn't changed, it's the preview system that has changed and it's now no longer visually accurate.

    I am uploading in STL format, the only format that Solidworks Outputs that is compatible with Shapeways systems and the industry standar for rapid prototyping.

    It was uploading perfectly before.

    So changing the upload format is neither practical, nor required :)

  5. svenpb
    svenpb New Member
    Looks like the java applet uses smooth shading instead of flat. In Rhino, depending on quality (weld etc.) of the STL, this also happens.

    Where did you find this the scale button?
    Last edited: Aug 6, 2008
  6. crisrose
    crisrose New Member
    when you upload, assuming that you haven't rescaled the STL file with Accutrans, select the Radio Button that says "Millimeters" rather than the default "Meters"

    It should upload then :)

    It's not a custom ratio/scaling tool, but it does mean you don't have to go through a 2nd program to upload standard STL files now! :D YAY!
  7. svenpb
    svenpb New Member
    aaaah...! that's a welcome utility too! I though you meant applet zoom :blush:
  8. crisrose
    crisrose New Member
    No, sadly there's no zoom on the preview yet, but the upload scale choice is a HUGE addition that will make many many lives much easier! :D Oh, and mine. lol
  9. Dalhimar
    Dalhimar New Member
    I do agree, the smoothing effect is a little misleading in that the printer dose not apply the smoothing at all, it takes the mesh at face value, quite literally using only the faces you have on the object.
    As such, i think it would be a good idea to try and give the viewer an option of "Estimated Printed Appearence" or something along those lines that shows it exactly how it will look when printed instead of with the smoothing.
  10. crisrose
    crisrose New Member
    i think the smoothing needs to be dropped entirely as it's misleading.

    it didn't have any smoothing on the preview before, and like you said, none will be applied, so i'm a little confused as to why it's been added.

    Any staff around to address the issue? I've emailed about it too about 12 hours ago just in case that's the response ;)
  11. WetMorgoth
    WetMorgoth New Member

    The smoothing issue is an interesting issue to deal with. When we turn it off, everyone complains their models look blocky, when we turn it on, everyone complains that it rounds the edges off. We can't win either way! :D

    Knowing when to smooth or not can be entirely dependent on the model format. Both X3D and Collada give us a crease angle parameter, which we can use to make that determination. STL does not, so we automatically smooth everything. That said, right now the pipeline ignores the crease angle and smooths everything. This is a known problem and related to the things taht we need to do on the backend during the model processing that require everything to be smoothed out. There are plans to be fixing it in a future version of the site, but can't give you a specific date yet other than that we're aware of it and have been for several months now. Other things have just had much higher priority.
  12. crisrose
    crisrose New Member
    Okay, so 2 questions:

    1. If the preview is not going to change back, i should just totally ignore previews and hope that it comes out like the STL model? If this is the case, does Shapeways take responsibility if the representation that's printed is inaccurate? After all, if i have no accurate preview to check, i can only trust that your system correctly analyzed it.

    2. is there any chance at all that you could just please everyone and take 2 preview snapshots that can be switched between? A "raw" capture, and a "smoothed" version? You can keep the smoothed version default if you like, and leave the raw version for power-users? I know that may seem like a fudge, but you have to understand that for people like myself that require the dimentional accuracy and are using the model as the first stage of a moulding process, it's pretty important.

    i totally understand that this isn't the most important thing for the site as a whole, but for anally retentive people such as myself, that really need to check and double check everything at every stage so time and money isn't wasted, i would rather that there was no preview at all, than a preview that bares little resemblance to what i'm having made :)

    Check the files i attached in my first 2 posts if you haven't already, and you'll see that it's not really suitable for the level of smoothing applied to it :)

    Thanks for reading and addressing this minor issue!

  13. WetMorgoth
    WetMorgoth New Member
    We're definitely not doing anything to the model under the covers. The triangles you give us are the triangles that get sent to the printer (unless you give us a file format that has primitives like spheres and boxes and we generate those triangles for you) in It is purely a visual artifact of the rendering infrastructure.
  14. svenpb
    svenpb New Member
    I think smooth shading is useless as a preview. I can create STL files that become unrecognizeable when smooth shaded.


    Attached Files:

    Last edited: Aug 7, 2008
  15. I also find that that the smoothed preview (both screenshot and 3D mode) is not a good idea.

    The preview should give a realistic idea on how the model will look when printed. It will not be printed smoothed, so it is very misleading.

    For pretty renders, one can always upload a picture...

    Oh an by the way, can you change the webserver so that middle-clicking these extra shots just show the image in the browser, instead of downloading it ? It would be much more convenient.
    Merely serving mime-type "image/jpeg" instead of the current wrong "application/octet-stream" should be enough.
  16. Wildsketch
    Wildsketch New Member
    I agree that displaying faceted models makes more sense than displaying smoothed normals.
  17. wormwood
    wormwood New Member
    I think it is very important that the model screenshot and 3D view are NOT smoothed in any way.

    This service is all about how models are built and their 3D reality when printed. Rendering the models with smoothing is of no practical use at all.

    The previews need to act as a proof in the same way that proofs are used in 2D commercial printing, so that there is no confusion over what the customer will actually receive when ordering a printed model. The previews also need to serve as a way of checking that a model has been processed correctly by the Shapeways system before placing an order.

    This also raises the issue of resolution. Would it be possible to have the upload system calculate a number for the average resolution of a printed model? It would be similar in use to the number that 2D images have for their resolution in DPI (dots per inch). I'm no mathematician but I guess the equation would be something like...

    F (total number of faces) divided by A (total surface area) equals VPC (vertices per centimeter)

    The VPC number could be a useful guide for how faceted/smooth a model will turn out when printed.
  18. crisrose
    crisrose New Member
    Many thanks to everyone that's replied to this issue. I'm glad it wasn't just me.

    It's good to see so many people realise that the snapshot generated from an uploaded model needs to be a "proof", even if that is merely to confirm to the person about to spend a hundred dollars getting this printed, that he's not going to get something turned inside out by an uploading glitch!

    I can totally understand the situation Shapeways is in, some say smoothed, some say unsmoothed. You can't please everyone.

    But i would argue that anyone that wishes to see a smoothed preview, needs to be educated properly about Rapid Prototyping, and gently informed of the reality of what their printout will look like.

    If they are unhappy with the faceted reality, perhaps this isn't the method of production for them? Perhaps it will just encourage them to increase the mesh density and face count.

    I would hate for anyone to feel mislead by the Preview images, and disappointed with their order.

    Wormwood - with relation to your suggestion of a "VPC" - i'm really not sure that sort of information would be that useful. If i take a flowing, curved model, and print it at 1cm with 50,000 faces, it will appear very smooth. If i then scale exactly the same model to 10cm, it will not seem as smooth. So the system you're suggesting appears to work in this situation.

    However, if i then design something that is extremely flat sided, with only 1 curved surface, then increases in mesh density become much less related to it's "overall quality".

    The information would be interesting to have, but with no way to predict how curved or flat faced users models are meant to be, Shapeways cannot offer a guide number to aim for. Without a guide, the numbers don't really help.

    It's great that with print - you can be told "300dpi for print quality". However a cube mesh with only 6 faces may look "higher quality" than a 25,000 face "monster head", even though the "VPC" is telling the user the exact opposite should be true. It doesn't matter if i scale it to 1cm or 100m, a cube requires no additional vertices to retain it's "quality".

    I think this is why no one has come up with a 3D version of DPI, apart from a face-count.

    Last edited: Aug 9, 2008
  19. wormwood
    wormwood New Member
    Crisrose, regarding VPC, obviously you are not wrong, but maybe we need to think outside the box.
    (pun intended ;)

    Even in 2D printing it is NOT enough to know just the DPI resolution of an image. You also need to know the type of image. Curves will look smooth when printed at 300 dpi as part of a CMYK image but if printed in just black on white they would need to be 1200 dpi to look smooth. And just like your 3D cube quality example, a 2D image of just coloured squares could in theory be printed at 1 dpi and still look hi res.

    My VPC equation was clearly way too simplistic. But maybe an SV (smoothness value) could be calculated by software that analyzed the model in more detail. The SV could possibly be calculated by analyzing the angle change of adjacent normals over their real world distance. The SV could be expressed as a percentage or a figure between 1 and 10 to a varying number of decimal places, or just rounded up to a whole number.

    For a cube, or any model where all the surfaces are flat, the SV could be expressed as either 100% or 0 or N/A.

    For models with a combination flat and curved surfaces, the flat surfaces would need to have more than 1 face so that the software could recognize them as intentionally flat. So then if 2 or more adjacent faces that shared a normal were followed by 2 or more faces at a different angle, but they also shared a normal, then the analyzing software would recognize that the angle change is not intended to be smooth and would ignore it when calculating the SV.

    At school I was crap at maths, so there's a very good chance I'm talking nonsense. And, as you mention, someone would probably have already come up with a 3D DPI or SV if it was possible.

    And I don't suppose any figure could be given by Shapeways to guarantee smoothness. It will probably always come down to the individual to decide if their model had enough faces. Much like when choosing the DPI for 2D printing.
  20. crisrose
    crisrose New Member
    sounds like the sort of algorithm, that were you able to perfect it, would make you a rich man wormwood lol

    in the meantime, i think a much larger, unsmoothed preview would go a long way to helping people visually determine whether or not the result is good enough ;)