What is the purpose of the Preview node in the Material room? It seems everything has one, and the only non-default setting I can ever see is the Diffuse color which can be anything. I guess Preview is the default texture before you add anything else to the object, but after that, does it serve a purpose?

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.

Argh!!! Of course it's a material and not a node! What was I thinking? Anyway, thanks for your answer. That's what I thought, even though I asked it all wrong.

It's like a little back pocket in the object's materials :)... I use it to quickly store experimental settings on whatever that thing might be, out of the way and easily applied with 'apply to all'. Only use I've ever had for it. If you're editing material lines within the text structure of a .pp2/.cr2 file be careful not to delete the Preview material, it will cause the figure/prop to load into the scene invisible. That is, always make sure to leave at least the Preview material intact.

What is the purpose of the Preview node in the Material room? It seems everything has one, and the only non-default setting I can ever see is the Diffuse color which can be anything. I guess Preview is the default texture before you add anything else to the object, but after that, does it serve a purpose?

The Preview Node is a safety feature. (AFAIK)

Every object that is to be seen in the OpenGL Preview/Posing Window or in any Render MUST have materials. As I understand it, recollecting from a very old discussion, the Preview node was originally added as a safety feature so that if an object was loaded without properly defined materials, or saved to the Library in such a manner, it would have some form of material node set.

By default, most 3D programs save file-types with some sort of material set. But, that means diddly if you strip them and have no material zones whatsoever, since nothing without a means to actually create material zones would be able to render them, no matter how complex or "large" the object is. I do not believe that Poser will automatically apply any "Preview" materials to such an object, though. However, at one time, Poser may have defaulted materials for some objects as "Preview." And, the OpenGL renderer in the Preview pane is not set up to default to rendering "Preview" materials, either.

But, if an object is UV'd, but somehow has no material zones, Poser "might" still use the default Preview material. Something I'd have to check on before confirming, though.