visibility polygon of a Point in an Environment or Polygon More...

#include <visilibity.hpp>

Inheritance diagram for VisiLibity::Visibility_Polygon:

Classes
class	Incident_Edge_Compare

struct	Polar_Edge

class	Polar_Point_With_Edge_Info

Public Member Functions
	Visibility_Polygon ()
	default to empty

	Visibility_Polygon (const Point &observer, const Environment &environment_temp, double epsilon=0.0)
	visibility set of a Point in an Environment More...

	Visibility_Polygon (const Point &observer, const Polygon &polygon_temp, double epsilon=0.0)
	visibility set of a Point in a Polygon More...

Point	observer () const
	location of observer which induced the visibility polygon

Public Member Functions inherited from VisiLibity::Polygon
	Polygon ()
	default to empty

	Polygon (const std::string &filename)
	construct from *.polygon file More...

	Polygon (const std::vector< Point > &vertices_temp)
	construct from vector of vertices More...

	Polygon (const Point &point0, const Point &point1, const Point &point2)
	construct triangle from 3 Points More...

const Point &	operator[] (unsigned i) const
	access with automatic wrap-around in forward direction More...

unsigned	n () const
	vertex count More...

unsigned	r () const
	reflex vertex count (nonconvex vertices) More...

bool	is_simple (double epsilon=0.0) const
	true iff Polygon is (epsilon) simple More...

bool	is_in_standard_form () const
	true iff lexicographically smallest vertex is first in the list of vertices representing the Polygon More...

double	boundary_length () const
	perimeter length

double	area () const

Point	centroid () const
	Polygon's centroid (center of mass) More...

double	diameter () const
	Euclidean diameter. More...

Bounding_Box	bbox () const
	box which fits snugly around the Polygon More...

std::vector< Point >	random_points (const unsigned &count, double epsilon=0.0) const

void	write_to_file (const std::string &filename, int fios_precision_temp=FIOS_PRECISION)
	write list of vertices to *.polygon file More...

Point &	operator[] (unsigned i)
	access with automatic wrap-around in forward direction More...

void	set_vertices (const std::vector< Point > &vertices_temp)
	set vertices using STL vector of Points

void	push_back (const Point &vertex_temp)
	push a Point onto the back of the vertex list

void	clear ()
	erase all vertices

void	enforce_standard_form ()
	enforces that the lexicographically smallest vertex is first in the list of vertices representing the Polygon More...

void	eliminate_redundant_vertices (double epsilon=0.0)
	eliminates vertices which are (epsilon) - colinear with their respective neighbors More...

void	reverse ()
	reverse (cyclic) order of vertices More...

Private Member Functions
bool	is_spike (const Point &observer, const Point &point1, const Point &point2, const Point &point3, double epsilon=0.0) const

void	chop_spikes_at_back (const Point &observer, double epsilon)

void	chop_spikes_at_wrap_around (const Point &observer, double epsilon)

void	chop_spikes (const Point &observer, double epsilon)

void	print_cv_and_ae (const Polar_Point_With_Edge_Info &current_vertex, const std::list< Polar_Edge >::iterator &active_edge)

Private Attributes
Point	observer_

Additional Inherited Members
Protected Attributes inherited from VisiLibity::Polygon
std::vector< Point >	vertices_

Detailed Description

visibility polygon of a Point in an Environment or Polygon

A Visibility_Polygon represents the closure of the set of all points in an environment which are {\it clearly visible} from a point (the observer). Two Points p1 and p2 are (mutually) {\it clearly visible} in an environment iff the relative interior of the line segment connecting p1 and p2 does not intersect the boundary of the environment.

Remarks: average case time complexity O(n log(n)), where n is the number of vertices in the Evironment (resp. Polygon). Note the Standard Library's sort() function performs O(n log(n)) comparisons (both average and worst-case) and the sort() member function of an STL list performs "approximately O(n log(n)) comparisons". For robustness, any Point (observer) should be epsilon -snapped to the environment boundary and vertices before computing its Visibility_Polygon (use the Point methods snap_to_vertices_of(...) and snap_to_boundary_of(...) ).

Constructor & Destructor Documentation

◆ Visibility_Polygon() [1/2]

VisiLibity::Visibility_Polygon::Visibility_Polygon	(	const Point &	observer,
		const Environment &	environment_temp,
		double	epsilon = `0.0`
	)

visibility set of a Point in an Environment

Author: Karl J. Obermeyer

Precondition: observer is in environment_temp (w/in epsilon ) and has been epsilon-snapped to the Environment using the method Point::snap_to_boundary_of() followed by (order is important) Point::snap_to_vertices_of(). environment_temp must be epsilon -valid. Test with Environment::is_valid(epsilon).

Remarks: O(n log(n)) average case time complexity, where n is the number of vertices in the Evironment (resp. Polygon).

◆ Visibility_Polygon() [2/2]

VisiLibity::Visibility_Polygon::Visibility_Polygon	(	const Point &	observer,
		const Polygon &	polygon_temp,
		double	epsilon = `0.0`
	)

visibility set of a Point in a Polygon

Precondition: observer is in polygon_temp (w/in epsilon ) and has been epsilon-snapped to the Polygon using the methods Point::snap_to_vertices_of() and Point::snap_to_boundary_of(). environment_temp must be epsilon -valid. Test with Environment::is_valid(epsilon).

Remarks: less efficient because constructs an Environment from a Polygon and then calls the other Visibility_Polygon constructor. O(n log(n)) average case time complexity, where n is the number of vertices in the Evironment (resp. Polygon).

The documentation for this class was generated from the following files:

src/visilibity.hpp
src/visilibity.cpp

Classes

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ Visibility_Polygon() [1/2]

◆ Visibility_Polygon() [2/2]