I know this has diverged a bit from the original "waxy leaf surface shader" topic, but I think it's best to continue posting to this thread rather than a new one.

My main interest is getting a nice leaf shader that I can use on all those old plant and tree models (and XFrog OBJs) that use one-sided transmapped squares for leaves.  This is a quick summary of what I think I've learnt over the past day:

• bagginsbill's scatter-based leaf shader doesn't seem to have a noticeable effect when applied to the leaves of the ivy in my render. Two likely reasons: (1) the scatter node requires a mesh with volume to work properly, and this ivy is one-sided transmapped squares; (2) my particular scene and lighting isn't a very good test.

• leaf translucence (assuming infinite lights with ray-traced shadows) is automatically handled by the basic diffuse channel, EXCEPT if the leaves are back-lit and viewed from the front.

• the translucence node of the Poser surface can be used to add leaf translucence (assuming infinite lights with ray-traced shadows) for back-lit front-viewed leaves. If used, it also seems to brighten up the leaves from other viewpoints (maybe some balancing of diffuse/translucence strengths required)

• the leaf translucence effect seems to require a basic Poser light with ray-traced shadows (I've only tried an infinite light so far). bagginsbill notes that it doesn't work with IDL. I've only tested with an infinite, so not sure about point/spot/diffuse IBL. It doesn't seem to work with depth-mapped shadows (I read somewhere that depth-mapped shadows are required for the fastscatter node, so that might be an option?)

And here are a couple of observations on problems with the standard leaf shaders - some might be easy to improve in the shader:

• most plants use a single leaf texture image (maybe two), so every leaf looks the same. Something in the shader to add a bit of randomness might be good?

• the bump image for most leaves is usually just a greyscale version of the texture image, so the veins appear raised, which is (usually) correct for the underside of a leaf, but wrong for the upper surface. Using a math subtract node, or GIMPing the image can correct this.

• the transmapped squares used for leaves are usually flat (i.e. the four vertices are coplanar). It may be possible to use displacement to warp each leaf slightly?

• the underside of a leaf is often very different from the upper surface. You really need a 3D mesh for this. But just maybe, the exploitable difference between front-lit and back-lit materials thread that bagginsbill linked to... ?

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The 3Dcheapskate (also available in DAZ and HiveWire3D flavours) occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.