Figure 1.

Diagram a) illustrates the bin structure of the 3D volumetric histogram during orientation assignment, shaded regions indicate non-zero histogram bins. From left to right, the primary orientation vector θ̂₁ is first determined, followed by a perpendicular secondary orientation θ̂₂ and finally θ̂₃. Diagram b) illustrates the GoH image intensity encoding in 3D that quantizes gradient samples uniformly in 8 spatial bins and 8 orientations bins.