# How to create intermediate vertices of a humpy surface (interpolation)

I took a cube, stretched it, added a number of intermediate edges and adjusted their height to get a humpy top surface.

Now, I want to get a smooth top surface by adding interpolated vertices. The existing edges must not change their position. How do I do this?

FYI: The object will be 3D-printed.

@eromod's hint was the solution.

• I created a huge ovoid (an icosphere that I compressed on one axis for an additional hump on the other axis),
• aligned it carefully manually,
• extended the original top surface in top direction,
• applied a boolean modifier with "Intersect" operation,
• and did a bit afterwork on the mesh.

Please leave a comment if there's something I forgot to do proper preparation for rounded edges around the top surface.

• Could you please clarify what is "huge ovoid" and "intersection modifier" ? Does the latter mean Ctrl+F > Intersection (Knife) ? Also please don't include new question in the answer; ask a new question instead. – Mr Zak Aug 3 '16 at 11:26
• To me, you may have problems with triangles on the lateral faces when printing – lemon Aug 3 '16 at 15:28
• Hm, (1) I'm only seeing triangles at the top, (2) the object will be 3D-printed at 0.1 mm with the SLS method (powder + laser) in nylon, which is quite good. So, I can't unterstand what effect you're referring to. – t_w Aug 3 '16 at 16:07
• I think the faces will be triangulated. This is not visible in your image here, but enter edit mode, select all the vertice then ctrl+T. I am not a specialist, but I am quite sure the 3D printer will translate it like that. To tell it in other way, lateral faces are big ngons. You may ask about that using another question. – lemon Aug 3 '16 at 17:07
• I see what you mean. I hope it gets resolved when rounding the edges around the top surface. – t_w Aug 3 '16 at 17:51

hold shift , select the opposing edges of a face, press W and choose subdivide . This will split a face in two.