In the current WIP, I added a fill light that doesn't cast shadows (for a second set of highlights) and played around with the highlight channel.

I'm not satisfied with the shaders yet but my thought was to broaden the highlight. I still wanted the small bright highlight to indicate glass but I was looking for some broader color to help show the shape of the glass.

So I used Mark D's iridesence shader to create a highlight that has a small white spot where the two lights create white spots and then a broad, dim color region. Not really satisfied with the result yet but I think the technique is promising.

Things I'd still like to fix (and would love suggestions on): The caustics for the glass base are too bright. In my actual scene, the arrangement will be such that this is probably not an issue. But any ideas on adjusting this?

The bottle shadow's internal detail is too crisp. Is there a way to blur this (without CS3-beta ;-)? I'm using GL with indirect light and caustics.

Marc