Hi, I am so confused about what exactly is tangent.w and unity_WorldTransformParams.w. I am still a beginner and trying to figure out what is actually going on, after some searching: What I know: Tangents in Unity are represented as Vector4, with x,y,z components defining the vector, and w used to flip the binormal if needed. W stores handedness and should always be 1 or -1. unity_WorldTransformParams is for odd-negative scale transforms. W is usually 1.0, or -1.0. If an object has odd-negative scale transforms, it means it's mirrored. Binormal of mirrored object should be flipped. What I am confused: Does tangent.w come with model from Maya or 3ds max, or is calculated by Unity? If it comes with model, what does it indicate? If it's calculated by Unity, how is it calculated? If tangent.w stores handedness, and Unity is left hand, does it mean tangent.w will be -1 if I set graphics API to OpenGL (right hand) and will be 1 if graphics API is set to Direct3D? Some forum mentions tangent.w handles mirroring, then what is unity_WorldTransformParams used for? (Originally I thought tangent.w handles handedness and unity_WorldTransformParams handles mirroring.) Thanks!