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3d Printing noob questions

I'm thinking about getting some 1-2" or so diving helmets printed out to give out at GDC. I haven't printed anything before so I have some qs:

1. I understand the mesh has to be water tight, but does it have to be completely merged together as well? Or in other words, can the mesh be made of of multiple separate objects as long as they are each water tight, or does it have to be one solid shell?
2. Any helpful tips/tutorials/etc for merging everything together and removing holes?
3. I would like to use the highpoly for this, but maybe that is dumb as its a bunch of meshes with holes, while the lowpoly is pretty much water tight already (would need some work). Thoughts?
4. Anything else I need to be concerned with?

Replies

  • cryrid
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    cryrid greentooth
    1.This might depend on the printer, but between the three I've worked with it was always ok to have things disconnected and pushed into each other. Just make sure that those parts are actually intersecting each other and not just snapped to the surface, otherwise they might not be connected in the print.

    2/3. The material and scale of the print is a factor to consider. If you opt for the smaller print then it's possible that some of the details aren't going to show up (2" might not even guarantee them). If the low poly looks good to you in a simple shaded mode then it very well could do the job all on its own. I find it's often surprising how well simple edges print out without needing bevels modeled in as the edges aren't going to be completely sharp once printed anyway.

    To quickly prepare highpoly models, I usually just dynamesh it with a high resolution and then run it through decimation master to cut the file size down. There's probably a few other similar alternatives to quickly patching things up; the topology won't need to be pretty or optimized in a way you'd be used to for real time rendering.

    4. Some materials are expensive, making it better to manually hollow out the model (like with ZCorp's ZPrinters). It could take some work to get a shell thickness that saved on material but was still structurally sound. If you're using a plastic based printer then you won't have to worry about that. You may still want to convert any tube-like parts (such as the hose) into a solid cylindrical shape instead; then the printer will fill it in with some support material instead of trying to print it hollow.
  • nyx702
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    nyx702 Polycount Sponsor
    For all the figs I have done they have always asked me to merge and dynamesh everything together then decimate just like cryid said. I only really have anecdotal tips. I'm not a 3d printing aficionado but there are some things I have picked up from clients.

    Most of the figs I have worked on are about 1-2" high and the minimum detail depth/extrusion I try and stick to is 0.4mm. I create a lil .4mm box that I move around to check that I am making details big enough.

    Also, some printers handle undercuts better than others. It seems less of an issue for newer machines? Extreme/negative undercuts I just tend to avoid.

    600px-3d_design_OverhangUndercut.jpg

    I have dealt with some conflicting things on this but I generally keep edges crisper than normal because it always comes out more softened than I anticipated. I'm sure that is something that depends on the printer as well.

    If you have the time get test print for sure. So much will be revealed once you get a test print. You should immediately see what you need to do differently.
  • mentalfrog
    1. Yes and No. Like mentioned it will vary on the printer. More so on the printing service than the actual printer being used. Some printers and software can't handle intersections. Printing services will sometimes say they can't when they can just so they don't have to deal with any issues that come with it and to keep their process more standardized.

    2. Dynamesh is a good way to merge and remove holes and maintaining enough detail. If your mesh is already water tight then you can skip the dynamesh step and just decimate it. Remember the topology is not important at all, just maintaining enough detail while keeping the file size down, which helps speed up the printing process (not the actual print time).

    3. Like mentioned it depends on your final print and the actual printer being used. You could get away with the low poly, but I usually recommend the dynamesh method for high poly followed by a decimation. Dynamesh should make it water tight and the decimation process will decrease the poly count, which again affects the file size and pre-printing software processing to the printer.

    Since your print is only 1"-2" you might want to consider taking out the tubing. It might be too thin to maintain its structure. You'll need to talk to your printing service and ask them about minimum thickness. Remember the piece has to stand on its own after it's printed. This means things like skinny legs can't structurally hold a heavy upper body or a lot of weight. In your case I think it'd be fine but again it might be too thin. It also depends on how much you think it adds to the piece, which could also influence if you want to keep it or not.


    Hollowing models is usually worth it, it almost always saves on material costs. Just be wary of wall thickness issues, not just going with the minimum thickness but how your model will stand up to its own weight and shape in real life. Undercuts and Overhangs can be an issue, but again this will vary on the actual printing process being used so ask your printing service.

    4. Remember that usually price = quality. Lower cost prints usually are lower because of a lower print resolution. There are more expensive materials such as metals vs plastics, but usually if comparing 2 plastics the cheaper one is usually sacrificing detail for price.

    You also need to know that you will lose detail in a print. First you lose detail when it gets sent to the printer. Then you'll usually lose additional detail in the post-print processing. Post-print processing varies from printers as well, sometimes it's a simple water cleaning process and sometimes it's a chemical bath type process, which can reduce details. Most prints I do have extreme exaggerated detail that wouldn't look good rendered out for CGI. They look great after the printing process is complete. So it's a different way of looking at what's on screen vs your final product.

    You need to know if you'll be doing any additional processing to the print after, such as painting. This can affect the material and cost of the actual print. Some materials are harder to paint than others and may take more processing time.

    A service like Shapeways can be great because they have a variety of printers and techniques. This gives you more variety to choose from to fit your needs. However if you know what you want then you can shop around a bit more with specialized services that have specific printers, you might even find a local one that might cost more but would be easier to deal with in person.

    The main thing I tell people is not to expect an exact replica of what's on their screen. People usually hear 3d printing and think it's this magical process that gets this grand detailed model exactly how they envision it. Those people are usually disappointed with the results, or shocked at the price it costs to get the results they actually want.

    3D prints can be great though. It's a wonderful medium to view a piece of work you've created digitally. If you have any specific questions or problems you can PM me. I do a lot of 3d printing on a daily basis.
  • JohnnyRaptor
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    JohnnyRaptor polycounter lvl 13
    good info by mentalfrog, see if i can add a bit more too

    I just got my own printer so iv had to go through a lot of this recently and learn from mistakes!


    1, as long as each element is watertight and they intersect with each other, it will print as one piece. Make sure your intersecting area/cross-section is large enough to create the strength you need.

    2, i use zbrush and dynamesh to merge things together in to one solid piece. Once that is done, you will need to error check your mesh, since dynamesh sometimes generates mesh with dodgy geometry integrity and this can cause problems during printing.

    So i would recommend exporting your mesh as an stl with the correct scale (in zb, using the 3d printing tool) and check it in Meshlab or Netfabb. They will highlight and fix the geometry problems most of the time.

    If you want to hollow out your mesh to save cost, wall thickness is really important here, i use meshmixer since it allows you to define in mm how thick you want the walls to be, and it also offers another important thing - air holes. If you hollow your mesh, you need to add holes for the air/print resin to escape and meshmixer has a neat feature for that too.
  • claydough
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    claydough polycounter lvl 10
    Gamasutra features a 3d print article today that discusses issues and option between home printing and cheap/expensive services...

    3D Printing for Game Characters (and more)


    IMG_4523%20copy%20SML.jpeg
  • EarthQuake
    Awesome, so much fantastic info, thank all of you so much!
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