I'm trying to see if I can use Blender for virtual surgery planning. I have an STL model of the patient's skull. I would like to cut out pieces of the skull and manipulate them. Here's an example of the cuts I would like to make enter image description here

What would be the easiest way to achieve this?

It seems to me that the easiest way would be if I could just draw the cut lines on the model. I think it would be enough if I could split just the outer surface with a curve.

So far I have tried using boolean operations to make the cuts. I can snap the vertices to the surface and then create a solid which I can use for the boolean operations. I'm just wondering if there's a more elegant solution to this problem.

  • $\begingroup$ I think your method is the easiest and more accurate way of doing it. I suggest Booltool addon. $\endgroup$
    – Mobin
    Commented Dec 30, 2019 at 12:04
  • $\begingroup$ Until STL's topology isn't a mess of self-intersecting triangles boolean is a most robust tool. You can draw curves on surface with grease pencil, but you still have to convert them to mesh and use booleans. $\endgroup$
    – Serge L
    Commented Dec 30, 2019 at 12:16
  • $\begingroup$ You could try subdividing, then using the knife project. $\endgroup$ Commented Dec 30, 2019 at 12:59

2 Answers 2


Thank you for the advice!

I used the grease pencil to mark the cut lines and booleans to split the skull into pieces. At first I drew the outline of the cuts on the skull, then decimated the mesh so I could edit the boolean meshes in real time. It worked quite well. It would be really nice if I could just draw the cut lines on the model. Here is the end result-->

enter image description here


Have 2 Times the same object from A original model set mesh view to outline only. Do Boolean union based upon A. You then might use sculpting tools to subtract from A and show only what they have in common.

Or maybe try to contact the sculpting developer to create a region paint split model. Currently blender is getting a lot sculpting updates. He might like to help you out on this I would if I could


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