[Geopdes-users] Second derivatives of nurbs basis functions

[李新康 <lix...@16...>]

Dear Rafael Vazquez,
       These days I am thinking on how to compute the second derivative of nurbs basis functions. I notice in GeoPDEs 1.0(I still use GeoPDEs version 1.0 because I think it is less difficult to understand than version 2), there are functions  'sp_bspline_2d_param' and 'sp_bspline_2d_phys' that can compute the second derivative of nurbs basis functions in parametric domain and physics domain respectively by making the option 'hessian' true, however, there's no function compute the second derivative of  nurbs functions.
       There are some mechanics problems need the second derivative of nurbs basis functions, such as Kichhoff plate problem. I find it is too difficult for me to add a function myself, so I ask for your help. Could you add a function in GeoPDEs that can get the hessian matrix of Gauss quadrature points in physical domain in structure 'sp', something like sp_nurbs_2d_phys(sp,msh,'gradient',ture,'hessian,true') and then we can get 'sp.shape_function_hessians' in structure 'sp'?
       I am very appreciate for your help.
       Thank you very much!


Yous sincerely,
Lee