vtkFlRenderWindowInteractor is a VTK class (actually FLTK too, but it helps to think of it as VTK) that enables VTK to render to and interact with your FLTK application. It is based on code by David Pont (the code was then called FlvtkInteractorWindow) which in its turn was partly based on the wxVTK code by David D. Marshall and Brian Todd. I reworked the code extensively to be simpler, more robust and bug-free(tm).

The main website is at http://cpbotha.net/software/vtkFlRenderWindowInteractor/