N variable in volumes mismatch when rendering

[jonp]

So I've been trying to speed up some heavy volume renders by exporting the volumes as i3d files. My volume shader is using the N variable for some stuff, but with the i3d it looks wrong. Initially it looked like N was in object/world space, but Z and X were flipped. Density etc. look fine, so this is puzzling. Is there a bug or do I have to do something special?

using H10.0.707

[jonp]

I ended up working around the problem by baking a 'nml' channel into the i3D with a negated volumegradientfromfile node. The volume shader then checks for 'nml' if it exists, and falls back to object space N if it doesn't. Not 100% correct solution but it works.