Is the normal map vertical lighting inverted? (Possible bug?)

(I figured it out, description below)

I’m having some strange results with normal mapping on my material.

Sideways the light looks correct. If the light is to the left, my object is lit from the left.

But in the up and down direction it seems inverted.

Here the light is lower but the light is hitting the rivets from above.

Here the light is above but hitting the rivets from below.

It’s easier to see when you put a light in the editor and move it around. You should see objects sticking out lit sideways correctly but vertically inverted.

The solution:

It’s my fault not unreal’s :smiley:

I noticed my other materials look correct.

The normals I baked directly from 3DS max were correct. But I’m using Quixel for this other material and its normal map is upside down so I need to flip the green channel I think. I can see that parts that are supposed to be facing up are the other color compared to a normal map that looks correct.

You guessed it, you need to flip a channel on the normal map. Can’t remember which one, but I think there is a simple checkbox for that in the texture viewer.

Yup, looks like the Green channel needs to be flipped.