GetSkinnedTrianglePositions(FSkeletalMeshAccessorHelper& Accessor,int32 Tri,FVector3f& OutPos0,FVector3f& OutPos1,FVector3f& OutPos2,FVector3f& OutPrev0,FVector3f& OutPrev1,FVector3f& OutPrev2,int32& Idx0,int32& Idx1,int32& Idx2)