BB, yeah, agree, thanks a lot for replying. So I still might be insane, but not for this reason :-)

Well, you know, in my personal opinion - and I can't look into the actual code - Poser is not tracing rays at all. It seems to apply some Consequetive Environment Mapping (CEM) instead. This means that each surface element builds some projection of the environment onto itself. For reflection this projection is mapped into its front (outside to outside, inside to inside), and for refraction its mapped onto its other side (outer to inner, inner to outer) while applying a spatial shift to mimic the bending. And it does so stepwise, to get reflections of reflections ... and refractions of refractions etc. I programmed that once, it's pretty efficient.

For the effect itself it's very hard to tell the difference from raytracing, but the object stays opaque, its easy to blur, easy to do something like raybias and easy to do some quality vs speed, and you can't do any kind of volumetric effect this way. Sounds familiar.

In Poser, it only takes the light diffused from surrounding objects into account. So reflections have to be accompanied by specularity to handle the direct lights themselves, and for refractions one has to work with transparency to get the shadows right and some light behind the object. But unfortunately transparency also deals with the light from surrounding objects too, so combining it with refraction means we get those objects twice, as you state.

Like we have to find the balance between reflection and specularity, we also have to find a balance between refraction and transparency. And a way to loose that object-doubling somewhat.

When some CEM is used indeed instead of raytracing, then nothing is really broke, and SM can't repair anything. Its just the algoritm itself which does not deliver what we like. They can add real raytracing instead, that's something different. And they can look into that double-shifting issue, which is just a matter of using the surface normals (pointing outward) properly. I'll run a test against that.

Now let's see how I can put all this into the New Great Material Room Missing Manuals.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though