Figure 4

Underlying principle of the graph construction for the interactive segmentation: The upper image shows how the nodes for the graph are sampled. Rays are distributed radially clockwise around a fixed point. Along these rays, the nodes (0, 1, …) are sampled. Bottom images: The intra-edges are constructed within the single rays (an example for two rays is shown in the leftmost image). The next step is to construct the inter-edges between the rays under the specification of the delta value Δ_r: for a delta value Δ_r of zero (Δ_r = 0), only inter-edges are allowed that connect nodes on the same “level” along the rays (see image in the middle). For a delta value Δ_r of one (Δ_r = 1), inter-edges are allowed that connect nodes on different “levels” along the rays, however, only with a maximum “level” distance of one (see rightmost image). Note: the delta values can also be higher, e.g., 2, 3 and so on. Note: figure adapted from²⁶.