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. Author manuscript; available in PMC: 2018 Oct 1.
Published in final edited form as: IEEE Trans Image Process. 2017 Jul 3;26(10):4900–4910. doi: 10.1109/TIP.2017.2722689

Fig. 5.

Fig. 5

Visualization of trilinear interpolation from equation 8 in two dimensions. The coordinate system is centered and rotated around the keypoint k. The descriptor is computed in a window of radius 2σ. The gradient magnitude at x is weighted according to its distance from the subregion centers yij, which enclose x in a square. In three dimensions, there are eight subregions yijk enclosing x in a cube.