Paritioning/Slicing 3D CCF objects

[hypercompetent]

Can we find a way to split CCF meshes into custom sub-regions?

For example, divide PAG into dmPAG/dlPAG, etc as shown here:
https://www.researchgate.net/figure/Circuitry-of-the-periaqueductal-gray-area-PAG-associated-with-defensive-behavior-In_fig5_263236478

Resources:
https://github.com/zarquon42b/mesheR
https://cran.r-project.org/web/packages/Rvcg/
http://zarquon42b.github.io/

[sourishmukh]

Alternatively, can this be done using custom coordinates? Perhaps defining Rostro-Caudal boundary planes for a certain structure, eg - PAG (-4.0mm to -4.4mm)?
Thanks!