Any example or tips to render sea surface(shader+FFT)?

Support
4

That example was made via shader. In VTK you can set shaders via one of the vtkMapper classes.

Please, take a look at this example: https://gitlab.kitware.com/vtk/vtk/blob/v7.0.0.rc2/Rendering/OpenGL2/Testing/Cxx/TestUserShader2.cxx .

I hope this helps getting you started.