r.cost
r.cost.full - Creates a raster layer of cumulative cost of moving across a raster layer whose cell values represent cost.
Raster (r.*)
ParameterRaster|input|Unit cost layer|False
ParameterVector|start_points|Start points|0|False
ParameterBoolean|-k|Use the 'Knight's move'; slower, but more accurate|False
ParameterBoolean|-n|Keep null values in output raster layer|False
OutputRaster|output|Cumulative cost