Calculate global stiffness matrix

Hi there folks,

does anyone around here knows about calculation of the stiffness and mass matrices?

I have a regular 3d grid. Some points are moved onto the object and the cuboids are marked whether they are inside or outside.

The inside cuboids form the object and I need to calculate the global mass and stiffness matrix.

Unfortunately I have no idea on how to to this for this 3d problem.

Thanks in advance if anyone is able to help 🙂