I was able to identify the solution for FMaterialAttributes. A sample .usf would be as such for reference (doesnt do anything but gets the point across):
# pragma once
struct shader {
FMaterialAttributes main(
float4 t0,
float4 t1,
float4 t2,
float4 t3)
{
FMaterialAttributes MA;
float4 o0,o1,o2;
o1.w = 0;
o2.x = 1;
o2.z = 0.5;
MA.BaseColor = o0.xyz;
MA.OpacityMask = o0.w;
MA.Metallic = o2.x;
MA.Roughness = 1 - o0.w;
return MA;
}
};
shader s;
return s.main(t0, t1, t2, t3);