Function gmsh_sys::gmshModelGetPrincipalCurvatures

pub unsafe extern "C" fn gmshModelGetPrincipalCurvatures(
    tag: c_int, 
    parametricCoord: *mut f64, 
    parametricCoord_n: usize, 
    curvatureMax: *mut *mut f64, 
    curvatureMax_n: *mut usize, 
    curvatureMin: *mut *mut f64, 
    curvatureMin_n: *mut usize, 
    directionMax: *mut *mut f64, 
    directionMax_n: *mut usize, 
    directionMin: *mut *mut f64, 
    directionMin_n: *mut usize, 
    ierr: *mut c_int
)

Evaluate the principal curvatures of the surface with tag tag at the parametric coordinates parametricCoord, as well as their respective directions. parametricCoord are given by pair of u and v coordinates, concatenated: [p1u, p1v, p2u, ...].