GRASS GIS 8.3.3dev Reference Manual: Topic cost surface

Topic: cost surface

r.cost	Creates a raster map showing the cumulative cost of moving between different geographic locations on an input raster map whose cell category values represent cost.
r.walk	Creates a raster map showing the anisotropic cumulative cost of moving between different geographic locations on an input raster map whose cell category values represent cost.

See also the corresponding keyword cost surface for additional references.