How do I cut this object in two?

[Elysia]

Hi.

I’m working on this object, and I want to cut it in two, so I get a tight fitting box and lid.

I have selected all the vertices along what I want to be the cut line. That in itself was a tedious process, and I’m sure there are easier ways.

What I have tried so far is to bevel the selected edges, extrude them and scale them inwards. I separated that as another object and tried to use boolean modifier to cut my ball i half. That created a very messy result, and also removes material, so that the two halves are not a tight fit any longer. I also tried to use the knife project tool, but with even worse results.

I’m pretty new to blender, so I would not be surprised if there is a completely different way to do this. Any help is highly appreciated.

The Blender file can be found on the dropbox link below.

Algeskjelett

[Richard_Marklew]

One option:
Select the edge along which you want to separate (both inside and outside the object)
Mark the edges as a seam (Ctr+E / Mark Seam)
Go to face select mode
With the mouse curser hovering over a face press L to select all its linked faces. If the marked seams completely surround the two halves of the mesh it will only select one half. If it selects all the mesh you have missed marking all the seams along which you want to cut
With one half of the mesh selected press P to separate it into a separate object

[Elysia]

Thank you!
That was the simple solution I was hoping for.