Flatten Surface algorithm?

Hi All,

I performed the surface flattening and plotted the deformation for the same double curved surface in Solidworks, NX and FreeCAD. All three give a different result for the deformations and boundary layout. So I am wondering which flattening algorithm is used in SolidWorks? Is it an LSCM? And is the deformation plot showing area or length distortion?

 

Thanks!