I use the RNM method, either by the program I wrote for it, but usually using Vincent Callebaut's Photoshop plugin; http://vincentcallebaut.com/CombineNormal.html Derivative normal maps get very simply blended by adding them together... but I don't think they're widely used, I wouldn't worry about those too much.
Hey guys! Wondering what techniques everyone has been using for blending two normal maps together- and if anyone out there prefers using both normal and height maps over blending normals. Basically, I know there are a variety of different ways you can blend normals together, some more arbitrary than others. This blog here…