Deformable registration in D

[Robert Jacques]

> Exp with finite support, how does this go?

The support of a function is basically the range in which its non-zero.  
See http://en.wikipedia.org/wiki/Support_(mathematics) for more details.  
I’m specifically using it to calculate the Gaussian, which is essentially  
exp(-x) where x > 0 (x is a distance). So I have a few small x’s which  
become relatively large exp(-x) and many large x’s that become really tiny  
exp(-x). By approximating all those large x’s (tiny exp(-x)) with zero  
(i.e. making the support finite) I don’t have to calculate as many exp  
functions, which speeds up the computation.