> Quote - ... > > If rendering with and without smoothing answers that question, then no. My previous render had smoothing on. This one has smoothing off. > > Smoothing applies a smooth, curved displacement interpolating across inter-polygon boundaries, within a single welded mesh containing at least two adjacent polygons. This is a single polygon, so smoothing cannot affect it.

Actually it kind of does. Note that Firefly is based on a REYES-algorithm (which i know from the internet and therefore must be true), which essentially means it subdivides your geometry always, you like it or not. If you have an older non-REYES (ie. Poser 5 or so) around, you can try render with that and it should rather look like the box on the right or like your preview. (Image made in blender, not REYES, but allows to subdivide manually[left box]).

However in any case the firefly renderer does not show what the  simulation calculates, so the preview is this case more close to the simulation than the render.