So I created a guardrail using BTB's wall feature, made the texture double-sided, and now the lighting is backwards. By backwards, I mean when the sun is on the trackside of the surface, it renders shadowed. Conversely, when it should be the shady side, it renders as if a light is shining on it. The lighting effect sort of reminds me of all those physic & engineering problems where you have to apply the "righthand rule" to get the torque right and I've inadvertantly used my left hand. Any easy ways to flip it back around? I suspect part of the problem is that I made the wall a single face with a double-sided texture rather than having two sides separated by a small distance and using a single-sided texture.