An important keyword is project
which allows to compute the interpolant of an expression with respect to a nodal function space over a part of the mesh or the whole mesh. The interface is as follows
Here are some examples:
A projection operator is available that supports:
You may want to customise the projected expression, that is to define your own expression. We have based that mechanism over the GiNaC librarie or the Functor.
The idea with GiNaC is to provide a string which will be parsed to generate a function:
To use the Functor, you have to define in the Feel namespace a struct with some variable. That struct will provide an operator()
interface with specific signature.
and then, you are allowed to define a functor based expression on that way: