I noticed that UE4 now supports no tangents bump mapping which made me wonder if actual derivative maps were going to be supported.
https://rocket.unrealengine.com/docs/ue4/INT/Engine/Subsystems/Rendering/LightingAndShadows/BumpMappingWithoutTangentSpace/index.html
They can already be baked in xNormal and generated in Knald from Normal/Height etc. and would be as simple as adding a normal map to a material to a user with all the benefits of no tangents and no need to use a complicated procedural shader 
A slot next to normal maps in the material editor would be perfect or maybe have the ability to swap between normal/derivative via a drop down or something.
Thanks!
You are right - no tangent bump maps in a step in that direction. It’s shouldn’t be hard to add the remaining bits and we might do that. You might be able doing that modifying the no tangent map shader functions.
However to take the full benefits the engine would need to be changed further - that would mean removing the stored tangents and not passing them as interpolators (also hull/domain shader). That however would be no good solution for mobile and mare some older hardware could run slower. Existing art (normal maps / shading) would become distorted.
Maintaining two code path there would be quite an effort (shader permutations, code complexity).
Cool. Thanks for the answer.
Heres hoping that it gets added.