Provided by: libgraphviz-dev_2.40.1-7_amd64

**NAME**

libpathplan- finds and smooths shortest paths

**SYNOPSIS**

#include <graphviz/pathplan.h> typedef struct Pxy_t { double x, y; } Pxy_t; typedef struct Pxy_t Ppoint_t; typedef struct Pxy_t Pvector_t; typedef struct Ppoly_t { Ppoint_t *ps; int pn; } Ppoly_t; typedef Ppoly_t Ppolyline_t; typedef struct Pedge_t { Ppoint_t a, b; } Pedge_t; typedef struct vconfig_s vconfig_t; #define POLYID_NONE #define POLYID_UNKNOWN int Pshortestpath(Ppoly_t *boundary, Ppoint_t endpoints[2], Ppolyline_t *output_route); vconfig_t *Pobsopen(Ppoly_t **obstacles, int n_obstacles); int Pobspath(vconfig_t *config, Ppoint_t p0, int poly0, Ppoint_t p1, int poly1, Ppolyline_t *output_route); void Pobsclose(vconfig_t *config); int Proutespline (Pedge_t *barriers, int n_barriers, Ppolyline_t input_route, Pvector_t endpoint_slopes[2], Ppolyline_t *output_route); int Ppolybarriers(Ppoly_t **polys, int n_polys, Pedge_t **barriers, int *n_barriers);

**DESCRIPTION**

libpathplanprovides functions for creating spline paths in the plane that are constrained by a polygonal boundary or obstacles to avoid. All polygons must be simple, but need not be convex.intPshortestpath(Ppoly_t*boundary,Ppoint_tendpoints[2],Ppolyline_t*output_route);The functionPshortestpathfinds a shortest path between two points in a simple polygon. The polygon is specified by a list of its vertices, in either clockwise or counterclockwise order. You pass endpoints interior to the polygon boundary. A shortest path connecting the points that remains in the polygon is returned inoutput_route. If either endpoint does not lie in the polygon, -1 is returned; otherwise, 0 is returned on success. The array of points inoutput_routeis static to the library. It should not be freed, and should be used before another call toPshortestpath.vconfig_t*Pobsopen(Ppoly_t**obstacles,intn_obstacles);Pobspath(vconfig_t*config,Ppoint_tp0,intpoly0,Ppoint_tp1,intpoly1,Ppolyline_t*output_route);voidPobsclose(vconfig_t*config);These functions find a shortest path between two points in the plane that contains polygonal obstacles (holes).Pobsopencreates a configuration (an opaque struct of type vconfig_t)onasetofobstacles.Then_obstaclesobstaclesaregiveninthearrayobstacles;thepointsofeachpolygonshouldbeinclockwiseorder.ThefunctionPobsclosefreesthedataallocatedinPobsopen.Pobspathfindsashortestpathbetweentheendpointsthatremainsoutsidetheobstacles.Iftheendpointsareknowntolieinsideobstacles,poly0or poly1shouldbesettotheindexintheobstaclesarray. If an endpoint is definitely not inside an obstacle, then POLYID_NONEshouldbepassed.Ifthecallerhasnotchecked,thenPOLYID_UNKNOWNshould be passed, and the path library will perform the test. The resulting shortest path is returned inoutput_route. Note that this function does not provide for a boundary polygon. The array of points stored inoutput_routeare allocated by the library, but should be freed by the user.intProutespline(Pedge_t*barriers,intn_barriers,Ppolyline_tinput_route,Pvector_tendpoint_slopes[2],Ppolyline_t*output_route);This function fits a cubic B-spline curve to a polyline path. The curve is constructed to avoid a set ofn_barriersbarrier line segments specified in the arraybarriers. If you start with polygonal obstacles, you can supply each polygon's edges as part of the barrier list. The polyline input_routeprovidesatemplateforthefinalpath;itisusuallytheoutput_routeof one of the shortest path finders, but it can be any simple path that doesn't cross any barrier segment. The input also allows the specification of desired slopes at the endpoints viaendpoint_slopes. These are specified as vectors. For example, to have an angle ofTat an endpoing, one could use(cos(T),sin(T)). A vector (0,0) means unconstrained slope. The output is returned inoutput_routeand consists of the control points of the B-spline. The function return 0 on success; a return value of -1 indicates failure. The array of points inoutput_routeis static to the library. It should not be freed, and should be used before another call toProutespline.intPpolybarriers(Ppoly_t**polys,intn_polys,Pedge_t**barriers,int*n_barriers);This is a utility function that converts an input list of polygons into an output list of barrier segments. The array of points inbarriersis static to the library. It should not be freed, and should be used before another call toPpolybarriers. The function returns 1 on success.

**BUGS**

The functionProutesplinedoes not guarantee that it will preserve the topology of the input path as regards the boundaries. For example, if some of the segments correspond to a small polygon, it may be possible that the final path has flipped over the obstacle.

**AUTHORS**

David Dobkin (dpd@cs.princeton.edu), Eleftherios Koutsofios (ek@research.att.com), Emden Gansner (erg@research.att.com). 01 APRIL 1997 LIBPATH(3)