mirror boundary condition in SPH method

[mohkh77]

Dear every one, I am studying SPH, and focusing on Fortran programs these days, and here i have questions about mirror particles.
Application of mirror particles is of great significance in simulation of rigid surface, and i know the physical variables for a mirror particle is symmetrical with corresponding particle's.
My equation is ,what are the most variablesl can i edit in this way .for example value for mass, density and hydrostatic pressure, and have opposite values for velocity in symmetrical derection. But how about stress deviator or shear stress, i am not sure for the equation for them.
Supposing a simulation in 2D condition, mirror particle J correspond with particle I in Y axis.

thank you so much