I have a cylinder and I want to create concave parts around it. Here what I did:
- add a sphere and position it on the cylinder surface, so only one half of the sphere is visible
- set the 3D cursor to the sphere
- set the 3D cursor XZ axis to 0 (so Y is the projection of the sphere)
- set the origin of the sphere to the 3D cursor
- add an empty (arrow) in this position
- select the sphere and add a modifier (array) using the empty as object offset (x6)
- rotate the empty to 60° to evenly space the 6 spheres
- apply the modifier and remove the empty
now I have all the 6 sphere around the cylinder's surface, and only one half of them is outside. Time to subtract them!
- select the ciylinder
- add a boolean modifier (difference)
- select the sphere as object
- remove the sphere
Well, it partially works: only the original sphere is actually subtracted from the cylinder. The other 5 spheres (created with the array modifier) are not subtracted.