Is there a partial update feature in vtk?

There is a polydata, about 5 million triangles, each rendering will modify a small number of triangles, about thousands, is there a similar function of partial rendering, so that its fps is higher, thank you!

Welcome to VTK @llibetter . There is nothing built in specifically for that use case. If the triangles are confined in some smaller spatial region relative to the overall mesh, you could split the mesh up into different pieces so that changes to the triangles require updates in the affected mappers and actors - that would speed up rendering compared to updating a mapper for all 5 million triangles ever render.