On Sat, 22 Dec 2007, Manoj Rajagopalan wrote: > I was browsing the source code to see how geometric objects like > spheres, cones, cylinders etc can be specified with dispersive materials > and after spending many hours I'm still lost. > > Am I right in understanding that solid geometry primitives are handled > by the interface to libctl? If so then how can I include such objects in > a pure C++ program?
Right. The C++ Meep code knows nothing about geometric objects. You just pass an arbitrary epsilon(r) function, which you can define in any way that you want. Originally, we just wrote our own functions to implement spheres, cylinders, etcetera, on a case-by-case basis. This is not too hard, usually. However, if you have lots of objects it is much faster to use libctl (or some other solid geometry library), since libctl has a tree-based logarithmic time lookup routine to find out which object goes with a given point. To use libctl's geometry routines directly, it is possible to link to libctlgeom.a (-lctlgeom). However, this is not really documented at the moment; you have to read the source code. > One method seems to be to declare a "double eps(vec const&)" > permittivity function which can contain information about the geometry > of the "scene" but I don't think this helps with dispersive materials. > If i understand correctly, this function will work only for simple > dielectrics or for monochromatic excitations. Right, in the C++ interface you specify the nondispersive epsilon via an eps(r) function. To specify the location of the dispersive material, you pass a sigma(r) function to add_polarization. And to specify the Kerr material, you pass a similar function to add_kerr, etc. Regards, Steven G. Johnson _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
