Reoriented Normal Blending | Unreal Engine material function

The "Reoriented Normal Blending" material function is a simple fix to the default "Blend Angle Corrected Normal" material function available by default in Unreal Engine.

This function allows you to blend two normal maps, by using the first normal map vectors as a new basis to reorient the second normal map vectors.

The default material function form Unreal has some error in the code that makes the "detail normal" get "flattened", and it gets worse the more you use them, unless you normalize your results after each blending operations, which quickly become costly in intructions.

Default : 144 instructions // Default + Normalize : 157 intructions // Reoriented Normal Blend : 147 instructions.

This fix corrects the "flattening" and does not require any normalisation after the operation, making it easier to use but also cheaper in instructions for a correct result.

Code is based from Stephen Hill's integration (https://blog.selfshadow.com/publications/blending-in-detail/)

"Reoriented Normal Blending" is FREE for use for any projects, personnal or commercial.