#399: Added "backlink" functionality to r.walk, r.cost & r.drain --------------------------+------------------------------------------------- Reporter: cnielsen | Owner: grass-dev@lists.osgeo.org Type: enhancement | Status: new Priority: major | Milestone: 6.4.0 Component: Raster | Version: unspecified Resolution: | Keywords: Platform: All | Cpu: All --------------------------+------------------------------------------------- Comment (by cnielsen):
Thanks for the testing and the how-to Dylan. I should emphasize that the changes I made only record the directions taken by the original cost accumulation algorithm. These means that I have not (well only a slight change to fix a mathematical error) changed how r.cost or r.walk calculates paths, only how those same paths are recorded and then turned into paths using r.drain. The clearest way I can put it is to think of the knight's move. With the old modules, r.drain had no way to tell if the cost surface was created with or without knight's move. Instead it just followed a water drop "drain" through the map only looking at 8 neighbours. Now it uses the direction surface to remember what the cost accumulation algorithm did and recreates that path. Therefore the cardinal directions are necessary (and precisely sufficient) since they record either eight directions, or for knight's move sixteen directions, based on the original moves... does that make sense? Also patches for grass_trunk aka grass70 are ready for testing (they work for me). -Colin -- Ticket URL: <http://trac.osgeo.org/grass/ticket/399#comment:21> GRASS GIS <http://grass.osgeo.org>
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