Part has only a density value:

Density value is assigned to part (contents + instance)

Part has no density value, but a mass value and a volume value:

Density is calculated from mass and volume and assigned to part (contents + instance)

Part has only a mass value:

Calculate volume using OSDM, then calculate and assign density (contents + instance)

First do the steps in Value = 0

Then

If a surface area value is given use it, else calculate surface value from surfaces of sub parts.

If a volume value is given use it, else calculate volume value from volumes of sub parts.

If a density value is given use it

ElseIf mass and volume values are given, calculate density from mass and volume values

ElseIf mass value is given, calculate density using mass value and the sum of volume values of sub parts.

Else calculate density as weighted average of all sub part densities. In the end assembly density is equal to assembly mass / assembly volume.

Let OSDM calculate centroid, principal axes and inertia tensor.

Assign PERMANENTLY to assembly these values (surface area, part volume, centroid, principal axes and inertia tensor)