Improper transparency sorting on some foliage

[Ophiolith]

I'm pretty sure this could actually be a limitation of OpenMW's postprocessing implementation, and frankly I'm not even sure if it's fixable, but nevertheless thought it worth drawing attention to - this is probably less noticeable with custom foliage, but at least on the default set there are notable transparency artifacts:

If it's unclear what is going on, fog and clouds do not render behind the foliage 'stencil' and so the regular sky and geometry before the fog pass renders through instead. It's fairly distracting.