Figure 1

Illustration of update order of algorithms, where circles are nodes on the grid. (a) Tracking order. Red nodes belong to the narrow band, describing the current front position. One node at a time is moved from the narrow band to the collection of already passed nodes (in blue). Nodes that have yet to be assigned a first value are empty circles. (b) The four sub-sweeps of the parallel marching method. Red nodes are being computed using values of nodes connected by arrows, which points in the direction of the sub-sweep. Nodes are coloured darker after each time their value has been updated.