The LA Times has another interview today with Stuart Craig.

JP: When dealing with CGI, do you suddenly see some things and think ‘that would be better computer-generated?’ Or do you just design everything as if you will physically have to build it?

SC: A lot of that has to do with physical limitations.  Obviously the actors would prefer a physically real set to react to and respond to as directed.  The CG effects encourage you to be bigger and more ambitious and scale things up, so what we try to do is build a physical set — which is always limited by the soundstage it’s on or the corner of the soundstage you have available — and then the CG extension becomes hugely important.  Most of our sets when we began “Harry Potter” were real or were fully realized prototypical sets, and now most of them are part built with a bigger part that’s a CG extension and then occasionally and increasingly, some sets are almost totally computer-generated.  We just build the floor that actors stand on.