What is the best way to blend two normal maps together? Why can’t I just add two normal maps together in Photoshop? I heard that to combine two normals together, you need to add the positive components and subtract the negative components, then renormalize. Looks right to me… Why shouldn’t I be using Overlay (or a series of Photoshop blend modes) to blend normal maps together? I want to add detail to surfaces. How does one combine normal maps in real-time so that the detail normal map follows the topology described by the base normal map?