[vtkusers] How to write a .VTI /VTK or raw file

[Rob Rotheram]

Hello Guys I need to write a vti / vtk file that can be opened in
volView or paraveiw
the data I need to write is generated by a custom function, wont go
into the detail of the function but it effectivity outputs a scaler
vector x,y,z and a magnitude between 0-0.4 I need it to be in a format
that volView or paraveiw can render it as a volume or isosurface.

any help be appreciative.

regards Robert Fletcher