Native interop

For C++ that takes VTK objects (C++/CLI, a native library of your own) and for SWIG modules that build on NetVtk's.

Native pointers

// the vtkObjectBase*, for C++ that takes VTK objects (C++/CLI, a native library of your own):
// valid while the proxy holds its reference
IntPtr pointer = polyData.NativePointer;

// a proxy for a pointer: a reference of its own, checked against the class asked for
using var same = vtkObjectBase.FromNativePointer<vtkPolyData>(pointer);
using var asBase = vtkObjectBase.FromNativePointer<vtkDataObject>(pointer);

• NativePointer is the object's vtkObjectBase*, valid while the proxy holds its reference: keep the proxy alive and undisposed while C++ uses it. IntPtr.Zero once disposed.
• vtkObjectBase.FromNativePointer<T>(pointer) gives a proxy with a reference of its own, or null for IntPtr.Zero. An object that isn't a T throws InvalidCastException, holding nothing.
• ownsReference: true makes the proxy take over a reference the caller holds (a pointer C++ got from New()) instead of adding one.

The SWIG files

The NetVtk package carries the SWIG interface files it was built from, in its swig/ folder:

Path	Holds
wrapper/	one SWIG module per VTK module, 25
common/	the typemap library: VTK objects and their references, strings, numbers, streams, directors, exceptions
extras/	the hand-written companions: the typed arrays' bulk members, the rendering modules' registration
headers/	each module's header and nested-type header
interop/	NetVtkInterop.i: NetVtk's objects in another SWIG binding
classes.json, modules.json	every type per VTK module, and the modules per native library

A binding on NetVtk

A SWIG binding of your own %includes interop/NetVtkInterop.i, not the typemap library, whose typemaps use NetVtk's internals and whose global ones would reach the binding's own classes. %netvtk_object(T) before a declaration that takes or returns NetVtk's T passes it as NetVtk's proxy (NativePointer in, FromNativePointer out, with NetVtk's reference rules); %netvtk_derived(T, Base) makes the binding's own VTK class T a subclass of NetVtk's proxy Base, whose (IntPtr, bool) constructor is protected internal for that, and %netvtk_new(T) gives it a C# constructor calling T::New().

The binding's native library compiles against VTK's headers but runs on the VTK libraries NetVtk.runtime.<rid> brings: build it against the same VTK. NetVtk's repository is a vcpkg registry of VTK's port (versions/); pinned at a NetVtk release's commit, with copies of netvtk-core/vcpkg/triplets and the features netvtk-core/vcpkg.json asks for, vcpkg builds the same VTK, with the same ABI hash, and either binary cache serves the other.