That's more like it!

The square peg in the square hole. For the rather simplistic sampling strategy I'm using at present, the occlusion culling is quite straight forward. Find the first micropolygon who's top-left vertex matches the sample coordinates. And yes you're right, no multipoint stochastic sampling here. But then why would I? I'm working in pixel units only and there are no rotated primitives, diagonal lines or curves.

As yet...