This class converts the costmap_2d into a set of lines (and points) More...

#include <costmap_to_lines_ransac.h>

Inheritance diagram for costmap_converter::CostmapToLinesDBSRANSAC:

Public Member Functions
virtual void	compute ()
	This method performs the actual work (conversion of the costmap to polygons)
	CostmapToLinesDBSRANSAC ()
	Constructor.
virtual void	initialize (ros::NodeHandle nh)
	Initialize the plugin.
virtual	~CostmapToLinesDBSRANSAC ()
	Destructor.
Static Public Member Functions
template<typename Point , typename LinePoint >
static bool	isInlier (const Point &point, const LinePoint &line_start, const LinePoint &line_end, double min_distance)
	Check if the candidate point is an inlier.
Protected Member Functions
bool	linearRegression (const std::vector< KeyPoint > &data, double &slope, double &intercept, double mean_x_out=NULL, double mean_y_out=NULL)
	Perform a simple linear regression in order to fit a straight line 'y = slope*x + intercept'.
bool	lineRansac (const std::vector< KeyPoint > &data, double inlier_distance, int no_iterations, int min_inliers, std::pair< KeyPoint, KeyPoint > &best_model, std::vector< KeyPoint > inliers=NULL, std::vector< KeyPoint > outliers=NULL)
	Find a straight line segment in a point cloud with RANSAC (without linear regression).
Protected Attributes
bool	ransac_convert_outlier_pts_
	If `true`, convert remaining outliers to single points.
bool	ransac_filter_remaining_outlier_pts_
	If `true`, filter the interior of remaining outliers and keep only keypoints of their convex hull.
double	ransac_inlier_distance_
	Maximum distance to the line segment for inliers.
int	ransac_min_inliers_
	Minimum numer of inliers required to form a line.
int	ransac_no_iterations_
	Number of ransac iterations.
int	ransac_remainig_outliers_
	Repeat ransac until the number of outliers is as specified here.
boost::random::mt19937	rnd_generator_
	Random number generator for ransac with default seed.
Private Member Functions
void	reconfigureCB (CostmapToLinesDBSRANSACConfig &config, uint32_t level)
	Callback for the dynamic_reconfigure node.
Private Attributes
dynamic_reconfigure::Server < CostmapToLinesDBSRANSACConfig > *	dynamic_recfg_
	Dynamic reconfigure server to allow config modifications at runtime.

Detailed Description

This class converts the costmap_2d into a set of lines (and points)

The conversion is performed in two stages: 1. Clusters in the costmap are collected using the DBSCAN Algorithm (https://en.wikipedia.org/wiki/DBSCAN) Reference: Ester, Martin; Kriegel, Hans-Peter; Sander, Jörg; Xu, Xiaowei, A density-based algorithm for discovering clusters in large spatial databases with noise. Proceedings of the Second International Conference on Knowledge Discovery and Data Mining. AAAI Press. 1996. pp. 226–231. ISBN 1-57735-004-9.

2. The RANSAC algorithm is used to find straight line segment models (https://en.wikipedia.org/wiki/RANSAC) RANSAC is called repeatedly to find multiple lines per cluster until the number of inliners is below a specific threshold. In that case the remaining outliers are used as points or keypoints of their convex hull are used as points (depending on a paramter). The latter one applies as a filter. The convex assumption is not strict in practice, since the remaining regions/cluster (line inliers are removed) should be dense and small. For details about the convex hull algorithm, refer to costmap_converter::CostmapToPolygonsDBSMCCH. Resulting lines of RANSAC are currently not refined by linear regression.

The output is a container of polygons (but each polygon does only contain a single vertex (point) or two vertices (line)

Definition at line 71 of file costmap_to_lines_ransac.h.

Constructor & Destructor Documentation

costmap_converter::CostmapToLinesDBSRANSAC::CostmapToLinesDBSRANSAC ( )

Constructor.

Definition at line 49 of file costmap_to_lines_ransac.cpp.

costmap_converter::CostmapToLinesDBSRANSAC::~CostmapToLinesDBSRANSAC ( ) [virtual]

Destructor.

Definition at line 54 of file costmap_to_lines_ransac.cpp.

Member Function Documentation

void costmap_converter::CostmapToLinesDBSRANSAC::compute ( ) [virtual]

This method performs the actual work (conversion of the costmap to polygons)

Reimplemented from costmap_converter::CostmapToPolygonsDBSMCCH.

Definition at line 101 of file costmap_to_lines_ransac.cpp.

void costmap_converter::CostmapToLinesDBSRANSAC::initialize ( ros::NodeHandle nh ) [virtual]

Initialize the plugin.

Parameters:

nh	Nodehandle that defines the namespace for parameters

Reimplemented from costmap_converter::CostmapToPolygonsDBSMCCH.

Definition at line 60 of file costmap_to_lines_ransac.cpp.

template<typename Point , typename LinePoint >

bool costmap_converter::CostmapToLinesDBSRANSAC::isInlier	(	const Point &	point,
		const LinePoint &	line_start,
		const LinePoint &	line_end,
		double	min_distance
	)		`[static]`

Check if the candidate point is an inlier.

Parameters:

point	generic 2D point type defining the reference point
line_start	generic 2D point type defining the start of the line
line_end	generic 2D point type defining the end of the line
min_distance	minimum distance allowed

Template Parameters:

Point	generic point type that should provide (writable) x and y member fiels.
LinePoint	generic point type that should provide (writable) x and y member fiels.

Returns:: true if inlier, false otherwise

Definition at line 173 of file costmap_to_lines_ransac.h.

bool costmap_converter::CostmapToLinesDBSRANSAC::linearRegression	(	const std::vector< KeyPoint > &	data,
		double &	slope,
		double &	intercept,
		double *	mean_x_out = `NULL`,
		double *	mean_y_out = `NULL`
	)		`[protected]`

Perform a simple linear regression in order to fit a straight line 'y = slope*x + intercept'.

Parameters:

	data	set of 2D data points
[out]	slope	The slope of the fitted line
[out]	intercept	The intercept / offset of the line
[out]	mean_x_out	mean of the x-values of the data [optional]
[out]	mean_y_out	mean of the y-values of the data [optional]

Returns:: true, if a valid line has been fitted, false otherwise.

Definition at line 250 of file costmap_to_lines_ransac.cpp.

bool costmap_converter::CostmapToLinesDBSRANSAC::lineRansac	(	const std::vector< KeyPoint > &	data,
		double	inlier_distance,
		int	no_iterations,
		int	min_inliers,
		std::pair< KeyPoint, KeyPoint > &	best_model,
		std::vector< KeyPoint > *	inliers = `NULL`,
		std::vector< KeyPoint > *	outliers = `NULL`
	)		`[protected]`

Find a straight line segment in a point cloud with RANSAC (without linear regression).

Parameters:

	data	set of 2D data points
	inlier_distance	maximum distance that inliers must satisfy
	no_iterations	number of RANSAC iterations
	min_inliers	minimum number of inliers to return true
[out]	best_model	start and end of the best straight line segment
[out]	inliers	inlier keypoints are written to this container [optional]
[out]	outliers	outlier keypoints are written to this container [optional]