The D-infinity flow assignment model is illustrated in Figure 6‑27.
Flows are assigned to two cells or pixels (colored here in gray) based on the direction of maximum gradient of the 8 triangular facets illustrated. The proportions assigned to each pixel are determined by the two ratios:
where α is defined in radians or degrees, as measured as in mathematics (i.e. from due east). In the D-infinity model, if the steepest slope vector angle illustrated lies outside of a facet (a special case that may well occur) then the direction vector is taken along the steepest edge of the facet.