HelpTutorialsHow I Made: A Skull Ring from a 3D Scan

How I Made: A Skull Ring from a 3D Scan


Translating organic models into 3D printable models Written by Carlos Tarjano

This tutorial is part of the "How I Made" series, written by designers in the Shapeways community to share their unique perspectives, design processes, tips, tricks, and tools.

I’ve been a nerd and into geeky things since I was a little kid. I always liked drawing, sculpting, and to make things. It felt like a revelation to me when I discovered computer modeling in 2005, enabling me to accomplish sculptures I never dreamed of before. When I heard about 3D printing, it was like a miracle, and brought together the best of both worlds: I could design stuff in the comfort of my room, without all the mess and bleeding fingers of physical sculpture, and still have that design brought to life. When I held my first 3D printed product in my hands it was nothing short of pure magic! I kept looking at the piece on my monitor and the one in my hands, and couldn’t help but feel great!

I've been a 3D printing enthusiast since the very beginning, when the price of the machines were just short of a million dollars. When Shapeways made it actually accessible it was a no-brainer: I simply had to do it!

Now that I'm almost finishing an Industrial Engineering degree, both with the extra time and expertise I acquired, I'm trying to turn my hobbies into my actual job.

I learned 3D modeling and about 3D printing by myself, with the invaluable help of the internet community, in the form of tutorials and forums. Blender, an open source, community maintained 3D modeling, animation, and rendering software was invaluable to me. Also, the feedback of the Shapeways users about my designs was invaluable to help refine the models in their early stages.

When you start 3D modeling be patient. Keep an eye on some details, like the texture your material of choice will have, and the effect of that in the aesthetics of your design, thin walls, consistent geometry and the scale the model is intended to have when printed. It’s always a good idea to start slow, and take note of the information available in the Shapeways site and forums in order to avoid frustrations.

1: Introduction
The purpose of this tutorial is to present one technique for translating organic models to a 3D printable model. I walk you step by step through the process, using a skull ring that I designed. So, let’s get started!

2: The Software

My workflow involves multiple software, but that’s not a prerequisite. You can use open source 3D modeling software, such as Blender, which are capable of handling the entire modeling and rendering process. In this tutorial I’ll be using:

  • Blender for low poly modeling
  • Zbrush for detail sculpting
  • Rhino for accurate resizing
  • 3: The Reference File

    I’ll be making a skull ring, so I gathered a real 3D medical scan I had lying around in my computer since 2010 and some other references. It’s important here to pay attention to copyrights, as not to use something you don’t have the right to. Below is the scan imported into Blender:

    4: Modeling!

    We are ready now to make the low poly model. I usually start with a plane, and proceed by extruding its edges. The result of this step will be something like this:

    We are ready now to make the low poly model. I usually start with a plane, and proceed by extruding its edges. The result of this step will be something like this:

    • Tip 1: While your base mesh is selected, go to the object tab in Blender (the one with the yellow box), then under “Display” choose in the “Maximum draw type” roll down list the “wire” option. That will make the low poly mesh transparent, while still allowing you to see the reference model.
    • Tip 2: Use the mirror modifier to simplify your work. Don’t forget to check the “clipping” option that prevents your vertex from crossing the middle of the canvas. Also, when finished, make sure all the central vertices are “glued” by selecting them and attempting to move to the sides: they must stay in place.

    Now, delete the mirror modifier (delete, do not apply it: we’re still working with only one side of the base skull), press Shift+c to ensure the cursor is placed in the center of the canvas, and create a circle, while in edit mode and top view (shortcut numpad 7), with 12 vertices. Then scale it to about the length of your base skull, delete the vertices that doesn’t lie in the upper right hand quadrant and extrude it along the z axis. Last, press Ctrl+R and choose the number of vertices in the end of your base mesh skull minus two. That should be the result:

    I learned that Shapeways hates pointed edges, heh. So I rounded off my corners slightly more! But I realized MeshSmooth modifier in Max just plain won't work for getting a clean, smooth object, which was critical for my earrings.

    So, I decided to go completely off into left field with this project, and model my earrings in 3DS Max entirely. I created a cylinder and slowly bent the cylinder to match the shape of my batwing object. I based it off my hand-sketch as a template, and the experience from Step 4 did save time. Nonetheless, 8 million hours later, I wound up with this:

    Both the end of the skull and the newly created quarter of cylinder must have the same number of vertices. You’ll now join each pair of closest vertices, by selecting both of them, hitting Alt+m and selecting “at center”. That way, you assure a smooth transition between the two pieces. Now, add another circle, again with 12 vertices, and scale it slightly smaller than your model. Delete half of it and extrude along the z axis to about the height of the model:

    Now, is the boring part of the work! You have to join these two parts, adding faces between them (select the vertices and hit F). Try to make them the closest possible to squares, and to perfect triangles, where squares are not possible. When finished, apply a mirror modifier and a subsurface modifier. Your end result should be somewhat close to this:

    5: Sculpting the Details

    Export the model as a .obj file (be sure to check “selection only” in the options), as we’re moving away from blender to Zbrush. While Blender offers sculpting tools, I still prefer Zbrush to this task. So open Zbrush, go to Tool>import tool and choose your exported skull.

    Hit CRTL+D several times to subdivide it, and you’re ready to go.

    Before sculpting, some advice: Mask the inside of the skull (CTRL+ left mouse button), so as not to lose the smooth cylinder we have. Hit the X key to enable mirror modeling. Add as much detail as you like, but keep in mind that the model is supposed to be printed: It will lose some detail, while gaining some texture from the material. Also, using a digital stylus, like a Wacom, at this moment is very helpful, even the cheapest models.

    • Tip 3: Instead of manually masking the inside of the skull, you can go to brush>auto masking and toggle backface auto mask. That will prevent you from messing up the inner cylinder while working in the face of the skull. Be aware that it won’t prevent messing the cylinder if you happen to click above it. After a fair amount of modeling, you should come up with something like this:

    The texture is not necessary, I made it for rendering purposes only. Now that’s the end of the artistic part. Some further steps are necessary to make this printer ready.

    6: Optimizing the Size

    Now, by this time you’ll probably have a extremely dense mesh. It will result in an unnecessary large file or, worse, one that exceeds the maximum file size allowed in Shapeways. To fix that use decimation master, a free Zbrush plugin from the Pixologic website. Once installed, in Zbrush, go to zplugin and choose decimation master. Hit ALT+F to see the wireframe of your model, and press “pre-process current” in the plugin window. After that, you’ll have to experiment with the level of decimation. Something about 100000 points is usually a nice compromise between file size and details. It’ll give you the density in the picture below. After that, re-export your ring as .obj file. We’re heading for the last part! Almost there!

    7: To the Printers!

    For the last part, I’ll be using a CAD software called Rhino to resize the ring. This step could be performed both in Zbrush or Blender, but I find that Rhino gives me more precision. In Rhino, as open the file, create a circle (in yellow, in the image below) with the desired radius and scale the ring so that the inner cylinder matches that radius. I use the USA / Canada ring sizes convention, so a number 10 ring would have an inner diameter of 19.76 mm. Be careful not to mix up diameter with radius! Now, export your ring again as an .obj file, and you know the rest: Upload it at Shapeways, set prices, choose materials and order a copy for yourself! You deserve it!

    One final note, I used a different workflow I used for my first version of the skull ring: I modeled the skull first, details and all, and then used boolean operation in Zbrush to punch a hole in it, and to crop the top of the head. It worked, but it wasn’t a very elegant method, and resulted in an unpleasant design. The workflow presented here is more appropriated and fun to use, resulting in elegant and smooth organic designs ready for printing. Besides, it can be applied to a variety of other models, like animals, faces, etc. I hope I could inspire, with this tutorial, more organic modelers to 3D print their models into life!

    Below is the whole skull family together.

    Did you enjoy learning about how Carlos created his unique skull ring? Let us know what else you'd like to see and learn from your fellow community members or inspire others with your own "How I Made" tutorial by reaching out at education@shapeways.com!

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