o.k., thx fr img, ice.  in bill's shader (above img), most channels are zero, including transparency.
he uses fresnel equation (sum of channels <= 0) and a method of fresnel effect via edge-blend.
refl. value always <= 1, and refr. value <= (1 - refl.) <= 1.  hence the question might be why there's
a shadow from such a shader.  I reckon it's because the refractive and reflective fx keep some
of the light from reaching the ground.  the part about reflections with no raytracing and no IDL is
not clear, as d3d's script may still be in effect after poser render screen and/or object properties
are changed.

it's true that in poser 4 the only way to make something transparent was to use the transparency
thing in the old materials screen, but look around and try to find something that has zero thickness
and is non-refractive.  the answer is easy: nothing.   a vacuum might have no refraction nor
scattering in intergalactic space, and we can see thru it because it seems to be transparent,
but that is the definition of "nothing", if we exclude any consideration of dark matter, which
ain't accounted for in any human rendering engine.