First of all friends, Happy New Year. <br /><br />It turns out that the
"roughness" option of the Oren Nayar shader has an upper limit
of the value in the magnitude of 3.14, which I suspect is the value of PI.
The relevant section of the page
<http://www.blender.org/manual/render/blender_render/materials/properties/diffuse_shaders.html>,
provides no information that there <em>is</em> and upper limit, much less
what the significance of the value is.<br /><br />Noel Stoutenburg