long message - double support, notifications, user feedback

[John Biddiscombe]

>A thought on point #1: can't you use MakeObject() ? This method (a 
>"virtual" constructor creates another object as the same type as the 
>calling object, like so:

Quite right. Sorry, I contradicted myself - on the one hand I said ignore
multiple inputs, on the other I gave my solution!. For single input filters
this will be fine. 

The real trouble is that 

float *pt1 = inPts->GetPoint(i,pt1);

is used in the vast majority of filters, and needs to be replaced (template
type approach?), with something that'll handle double as well.

JB