# Using Added Mass in PhysX based simulations

Hi,

I wonder if PhysX is able to handle “added mass” properties in its dynamics for rigid body. The question is very relevant in order to use PhysX as a solver for conducting ship simulation research in my PhD project. All mathematical models for ship dynamics account for a term proportional to the acceleration of the body (x,y,z) with different coefficients in x, y and z components. In practical terms, it represents having a Mass Matrix that is not uniform in the main diagonal, something that we cannot set using regular PhysX API.

Thank you,

Claudio

I’m a little confused by your question. Typically for a force applied to the center of mass of a rigid body we would say F = m.A where F and A are vectors and m is a scalar. Are you saying that in ship simulation you would say F = M.A where M is a diagonal matrix whose terms are not equal?

If so, could you not simply scale your force to achieve the same effect? i.e. if you wanted to solve the equation
░░[1 0 0]
F = [0 2 0].m.A
░░[0 0 3]
could you not instead solve the equivalent equation

░░[1 0 0 ]
F’ = [0 1/2 0 ].F = m.A
░░[0 0 1/3]