I know nodes own the geometry, but how can I differentiate between the types of geometry coming in? For instance, the sphere SOP has different primitive types (mesh, nurbs, bezier,polygon etc) so the representation in the SOP node , the geometry which is retrieved through gdp should have the geometric type info in it?? I guess I should look into the GEO and GU classes??

thanks

gdp isn't a type of geometry. It's a geometry data pointer. It can points to all types of geometry. To specify the type look at HDK classes like GU_Detail, GU_PrimCircle and so on. Check doxygen docs to find all the stuff you need.

Thanks ..I'll look into those classes immediately.