ss reflections tweakage:

+		// Offset the guess source a little according to a trivial
+		// checkerboard dither function and spec.a.
+		// This is meant to be similar to sampling a blurred version
+		// of the diffuse map.  LOD would be better in that regard.
+		// The goal of the blur is to soften reflections in surfaces
+		// with low shinyness, and also to disguise our lameness.