Subtract the volume of one shell from another

1. Choose Surface Edit > Shells > Shell Subtract.
2. Click the shell the will be subtracted from.
3. Click the shell whose volume will be subtracted from the first shell.

Delete all but the intersecting volume between two shells

1. Choose Surface Edit > Shells > Shell Intersect.
2. Click the two shells whose intersecting volume you want to keep.

Combine the volumes of two shells

1. Choose Surface Edit > Shells > Shell Union.
2. Click the two shells whose volume you want to combine.

What if...?

A boolean operation does not work?

• Make sure the shell’s normals are pointing outward. (See Reverse the direction of a curve or surface for more information.)
• Boolean operations may not work on shells that contain problematic geometry such as collapsed sides or multi-knots. (See Simplify objects for more information.)
• Boolean operations may not work on shells that have open edges. Use Object Edit > Query Edit to check for open edges. If CLOSED VOLUME is True, there are no open edges. Otherwise, the number of open edges is given, and they are clearly indicated by red arrows.

I want to work with multiple shells at once?

Group the shells and perform the boolean operations on the groups.

See Group and ungroup objects.