The SIFT descriptor is a popular method for describing selected feature points based on local

neighborhood properties so that they can be matched reliably across images. Assuming feature points

have been previously detected using the SIFT feature detector, $($i$)$ briefly describe the main steps of

creating the SIFT feature descriptor at a given feature point, and $($ii$)$ name three $(3)$ scene or image

changes that the SIFT descriptor is invariant to $($i$.$e$.,$ relatively insensitive to$).$