How to import 3D data into a function space?

[dokken]

@quadruplefish

I have stored discrete mass density data in ‘grid_density’ of size (10, 10, 10), and I wish to interpolate or project this data into the defined function space to compute the Poisson equation.

Is grid_density just a numpy ndarray?
If so consider Manipulating images - #2 by bleyerj
Which covers the 2D case, and is easy to extend to 3D