Always creates blank white textures whenever I used multi-layering in Reality, either that or entirely overwrites it and removes the overlay entirely. Never really had much luck with it myself.
The best way to use a layered image in Luxrender is to not use one…take the overlay and the texture into an image editor and combine them. This is because, instead of looking at it as a layered image, it is most likely being interpreted as a layered texture…sort of like hair.
Also, the ‘collect textures’ option should be the default, because Lux works best when it doesn’t have to hunt down the textures. (from experience, it seems that no matter what, it will have problems finding something if they aren’t all in one place). Another advantage with the collect feature, everything is one folder, so setting it up for a network/distributed render is a lot easier. And if you need to, you can edit any of the lx files…
lxs=Lux Scene File…it’s the description of the ‘world’ and the render settings.
lxm=This is the materials file…and the one that will need to be edited if you give the combined layer/image a different name.
lxo= Geometry definition file.
flm= the ‘progress’ file…it stores a ‘film’ of how far/what has been done so far so that the render can be paused/stopped/resumed…not really editable.
As to how LIE works, yes, it stores the images in the DS TEMP folder…