Normal Blend Nodes

A collection of various normal map blending nodes, including the implementations of Substance Painter's Normal Map Combine and Normal Map Detail.

Most of the knowledge and formulas for these node groups are from Colin Barré-Brisebois' and Stephen Hill's publication Blending in Detail:
https://blog.selfshadow.com/publications/blending-in-detail/

Many of their references and some further references in regard to each blend mode that have been examined to create this set of node groups are listed below.

License: Creative Commons CC0 1.0 Universal (CC-0)

Blending Nodes 

• Linear Blending:
  
  • Colin Barré-Brisebois and Stephen Hill, Blending in Detail - Linear Blending, 2012
• Linear XY Blending (UDN Blending, Detail Normal Map):
  
  • Colin Barré-Brisebois and Stephen Hill, Blending in Detail - UDN Blending, 2012
    Material Basics: Detail Normal Map, Unreal Developer Network
• Overlay Blending:
  
  • Colin Barré-Brisebois and Stephen Hill, Blending in Detail - Overlay Blending, 2012
    
  • GIMP Docs, Combining Images, Layer Modes - Overlay
• Partial Derivative Blending (PD Blending): 
  
  • Colin Barré-Brisebois and Stephen Hill, Blending in Detail - Partial Derivative Blending, 2012
    
  • Jörn Loviscach, Care and Feeding of Normal Vectors, ShaderX^6, Charles River Media, 2008
    
  • Morten S. Mikkelsen, How to do more generic mixing of derivative maps?, 2012
• Whiteout Blending (Substance Painter's Normal Map Combine):
  
  • Christopher Oat, Real-Time Wrinkles, Advanced Real-Time Rendering in 3D Graphics and Games, SIGGRAPH Course, 2007
    
  • Substance Painter Docs, Blending Modes, Normal Map Combine
    
• Reoriented Blending (Substance Painter's Normal Map Detail):
  • Colin Barré-Brisebois and Stephen Hill, Blending in Detail - Detail Oriented, 2012
  • Colin Barré-Brisebois and Stephen Hill, Blending in Detail - The Nitty Gritty, 2012
  • Stephen Hill (selfshadow), Reoriented Normal Mapping [...] for unpacked, normalised vectors, 2013
  • Substance Painter Docs, Blending Modes, Normal Map Detail
    To achive Substance Painter's Normal Map Detail Inverse, swap the Normal 1 and Normal 2 inputs of the node.
• Warp Blending (Unity Blending):
  • Colin Barré-Brisebois and Stephen Hill, Blending in Detail - Unity Blending, 2012
  • Renaldas Zioma and Simon Green, Mastering DirectX 11 with Unity, GDC 2012