I am looking at a raster layer where each cell has one of 8 values, indicating where flow from the cell is directed. Is there a way to select any given cell, and have a line drawn which will follow the direction of cells as it reaches them. This can be thought about like a hydrology flow map essentially, using flow direction to draw a path along cells until we reach a pit or output cell. Is there any code out there which may help? I'm sure this must have been done before somewhere.