Is there a function to delete all unused materials that I am missing in H15?

An option to display only the used, unused or all materials would be more useful, because then it's a simple matter of selecting them and deleting them all (whatever “all” might refer to - unused, etc)

McNistor
An option to display only the used, unused or all materials would be more useful, because then it's a simple matter of selecting them and deleting them all (whatever “all” might refer to - unused, etc)

But it only work with material that assign to whole Object. Not showed those reference by Material Sop.

It could be scripted. Simply scan all nodes by children looking for node types of Material. Or work backwards, scan for all SHOP type nodes, collect up shader node names and then scan for matches.

Blender has a nice feature that is part of each node/datablock. It is simply a user count. When count is zero there are no users of that data and it can be safely removed from the scene.

Not sure how that would affect delayed load items, however…

I have a feeling it probably isn't simple to account for all the possible ways a material is being used, hence the option for mantra to embed all materials in the scene into the IFD… otherwise there would probably already be code in SOHO to find them more efficiently.

You could script for the simplest case pretty easily, just check for a “shop_materialpath” parameter on object nodes and delete any nodes that aren't referenced there.