For some concrete examples, is there an easy way to describe the virtual fundamental class (say, by capping off the moduli pace with an obstruction bundle ). Consider the moduli space of stable maps into $\mathbb P^r$. For genus $0$, the virtual class is just the usual fundamental class. For genus $1$, it is not, which is why Gromov-Witten does not count curves. What is the description of the virtual fundamental class in this case?