middle surface from two other surfaces


I am an engineer (translated NOT an artist;)) working on a study involving modeling bone joints. I have 3-D surfaces of a couple of bones and can easily select out the parts I am interested in with blender. Now the challenge is I want to create surface that is between the two surfaces.

I would like the surface to be made from the normals of each surface pointed at the other with the new surface being located in the middle.

I have tried to extrude each surface and do a boolean but the computer just sits working away forever. This is an imported stl which is obviously very dense so maybe I need to simplify and retry that.

Thanks for any suggestions,



I would duplicate the 2 objects (so you’re not working on the original)
then join them as one mesh

then you could try a few things

  1. select edges and verts from each side and create faces
  2. you could try to bridge the faces with the script that is in the scripts menu (but you will need the same amount of verts each side)
  3. select one side - extrude the edges toward the other side just a little - then move, scale and reposition the new verts and repeat the extrude until you reach the other side

or you could model a brand new object between the 2 objects - and then trim the ends with the boolean.
I’m pretty sure Boolean will only work with a closed mesh (it looks like you have an object with no thickness)

hope this helps you

Thanks for the suggestions Waylow,

Unfortunately, for my project we need this to be objective so manually dragging vertices around will not work:(. I have done a bit more work and using poly reduce was able to get boolean to run through but I don’t get an intersection like I want. I tried both the normal boolean and the Megabool python script. They both seemed to give a difference and/or a union vs. an intersection. Do I have to prepare the mesh in a certain way?

The attached pic shows two pairs of overlapping surfaces that I extruded through each other. I hope to get the intersection ‘volume’ then find a way to split it in half.

The more I get used to the program the more impressed I am in what it can do especially being free and all.