You need to multiply the two matrices.
1 0 0 0 0 -1 0 -1 0 will translate the LDraw orientation into your game engine's orientation. But it must be applied on top of the original type 1 line matrix.
I'm not families with the unreal 4 backend but I would be surprised if there isn't some matrix component block you connect the 'f' rotation block to.
1 0 0 0 0 -1 0 -1 0 will translate the LDraw orientation into your game engine's orientation. But it must be applied on top of the original type 1 line matrix.
I'm not families with the unreal 4 backend but I would be surprised if there isn't some matrix component block you connect the 'f' rotation block to.