[quote="Ashley":26mfloty]This is a good idea for C2, but per pixel isn't much of a waste of resources. At 1 bit per pixel for a collision mask you're only using 128kb of memory for a 1024x1024 object, on machines which these days typically have well over 1gb physical RAM going spare.[/quote:26mfloty]
I think he means processing time, which is significantly larger for per-pixel than bounding box.
Did you try dummy box objects? they are *exactly* what you're looking for.