Render fuction cost too much time on repaint

I received 15 million points,use vtk & c# to show them.
when i use renderWindow to call fuction “render” (render window and render is already global
vars),it costs 1.3s(have not interact yet). The repaint time is too long.
I want to know how to solve the problem?

Andras Lasso
That should be no problem to render at the maximum screen refresh rate.

I tried to use LODActor ,then SetDesiredUpdateRate and SetStillUpdateRate both to 500,but renWindow->Render() still cost 1.3s time. May be the 1.3s costs on repaint
(opengl fuctions draw on conrol and refresh), have not start to interaction yet.