[Paraview] Building plugin with sources in different directory

[David Doria]

If I have my cxx and h files for my filter in ..../MyFilter

then in ..../MyFilter/plugin I have the MyFilter.xml. I also have a
CMakeLists.txt containing

ADD_PARAVIEW_PLUGIN(MyPlugin "1.0"
  SERVER_MANAGER_XML MyPlugin.xml
SERVER_MANAGER_SOURCES ../MyPlugin.cxx
)

You'll notice the ../MyPlugin.cxx because the filter sources are not
in the plugin directory.

When I try to build I get an error:
MyFilterClientServer.cxx error: MyFilter.h: No such file or directory

I'm assuming this is because it is looking in the current directory.
Is there a way to specify where the sources reside?

Thanks,

David