Is there a way to subtract 3d geometries

[jakubMitura14]

Hello a question rather then issue: I would like to subtract a cylinder from bigger cylinder to get a hollow one - is there a way to subtract two geometries?

[JeffFessler]

You just need a negative value for the amplitude parameter.
The Shepp Logan phantoms do this:

ImagePhantoms.jl/src/shepplogan.jl

Line 163 in 05f851e

0.22 0 0.31 0.11 72 -0.02 # right big

Because overlapping objects are "added" by phantom etc.