I'm confused about IOR in Blender Internal as used in raytraced transparency. To demonstrate my issue, I set up a camera looking through a transparent sheet with IOR>1 (and slightly tinted) at a textured surface. You can clearly see the expected refraction.
But when I flip normals, I get exactly the same render! My question is therefore: How does Blender Internal determine the "in/out"-side if it does not use the normals for that?
Placing the camera inside a properly closed transparent volume with IOR does not change anything.
Clearly, I can invert the IOR to treat camera rays, but I came across this issue when reflections going out and then back into the glass material misbehaved.