I wonder how to compute the tangents and normal planes of a curve at a point on it using VTK. I have searched it on the Internet but cannot get a clear answer. Can anyone help me?
You can use vtkFrenetSerretFrame. See example here: https://lorensen.github.io/VTKExamples/site/Cxx/Remote/FrenetSerretFrame/.
The class is in a remote VTK module. If you have trouble configuring VTK to retrieve the remote module then you can grab the classes from GitHub.
Need for this class comes up quite often. We may consider adding it to VTK proper.
It perfectly solved my problem. Thank you very much!