Question about texture Coordinate Index

I have a very basic example material in which I’m blending two Normals.
It’s the Trim Sheet technique where I’m using one normal map information in one UV Channel and a tillable texture and normal information on a second UV channel.

Note that I’ve swapped the UV channel position on the example as the Trim Sheet normal is easier to see the effect that is occurring.


Here is Material preview with TexCoord set to 0

And here it is with TexCoord set to 1.
It seem to be with a much large tilling as well as mirrored, with the channels flipped, miss aligned. Just all over the place

Is there any particularity about UV Channel 1 or is it a bug? Same thing happens with Channel 3 (Odd numbers?)

Version: 4.17.2-3658906+++UE4+Release-4.17

Thanks for the help.

Have you tried this material on a custom mesh and not the built in UE preview mesh?

Might just be the UE preview mesh issue.

Tangent space normal maps will work only on UV0. It is expected.