What are the differences between Maya's Z-Up and UE4's where directions are concerned?

Development Rendering
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1

I have a ‘forward vector’ in Maya, and it gets exported along with the animations, UE4 reads it. It’s for a material.

My understanding was that UE4 flips the Y axis so +Y is forward whereas in Maya (Z-Up) -Y is the forward, so I figured inverting the direction would suffice, but that isn’t the case.

I’ve tried a lot of combinations trying to guess the conversion but I can’t. Here is an image showing what I mean.

2

My problems were elsewhere, the answer is an input of 0,0,-1 for the input matrix and then multiplying the Y by -1. That will convert a maya forward vector that aims down -Z to UE4 forward vector.