I don't know the reasoning that went into the behavior of adding a "Preview" material (not a node, a material) to every object Poser loads. (Node's are the little boxes of functionality we use to assemble a "shader" which you load into a "material". )

Maybe long ago a version of Poser existed that would use the Preview material to render in Preview renderer, and other materials to render in ... not the preview renderer. I don't know. As far as I can tell this is pointless behavior. No polygons will render with this material when Poser adds it.

I have occasionally taken advantage of it by making objects that define their only material zone as Preview, instead of some better name, simply because Poser imports and adds Preview to everything whether you need it or not.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)