Shown always, only affects layers where
Autodetect Textures is on. On by default. A checkbox which turns on or off the compiling of normal textures from existing normal and/or specular textures as needed. Given a detected normal texture, specular texture, or both, XPlane2Blender will create a combined image and save it to disk (with the suffix "_nm", "_nm_spec", or "_spec" depending on what was used in the generated file). This will be referenced in the OBJ as a replacement for the regular normal or draped normal file.