Reggrid Class Reference

A regular grid datastructure used for finding points within a fixed range. More...

#include <reggrid.h>

List of all members.

Public Member Functions
bool	TestCollision (const cml::vector2f &point, float distance) const
	Check for collision using an arbitrary distance as the testing distance.
	Reggrid (float width, float height, float separatingDistance, float testingDistance)
	Regular grid constructor.
const vector< cml::vector2f > &	GetCell (int cellId) const
	Gets a const list (std::vector) of point for a given cell.
vector< cml::vector2f > &	GetCell (int cellId)
	Gets a list (std::vector) of point for a given cell.
bool	Collides (const cml::vector2f &point) const
	Check for collision using the intersection conditions, ie.
bool	SeedCollides (const cml::vector2f &point) const
	Check for collision using the seed conditions, ie.
float	GetTaperingSize (const cml::vector2f &point) const
bool	AreCoordsValid (int x, int y) const
	Check whether the cell coordinates are valid.
bool	AreCoordsValid (const cml::vector2f &point) const
void	GetCoordsFromID (int cellId, int &x, int &y) const
	Calculates the cell's x,y coordinates from a cell's ID.
int	GetCellIDFromCoords (float x, float y) const
	Calculates the cell id from coordinates (in the space defined by the parameter's constructor).
int	GetCellIDFromCellCoords (int x, int y) const
	Calculates the cell id from cell coordinates.
void	AddPoint (const cml::vector2f &point)
	Add a point to the reggrid, without testing for any conditions.
Public Attributes
float	m_separatingDistance
	Separating distance, as defined in the paper.
float	m_testingDistance
	Testing distance, as defined in the paper, always <= separating distance.
float	m_width
	Actual width of the grid, ie. a multiple of m_separatingDistance.
float	m_height
	Actual height of the grid, ie. a multiple of m_separatingDistance.
int	m_cellsX
	Width of the grid, in cells.
int	m_cellsY
	Height of the grid, in cells.
vector< cml::vector2f > *	m_grid
	The grid itself.

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Detailed Description

A regular grid datastructure used for finding points within a fixed range.

Basically, two parameters, the separating distance Dsep, and the testing distance Dtest are taken as input parameters, under the condition that Dtest <= Dseparating, and testing for those distances is then enabled.

The internals of this datastructure are following: first, the size is enlarged to a multiple of the Dsep distance, so if Dsep = 0.5 and the requested size of the grid is 2.3 and 4.1, the actual size of the grid will be 2.5 and 4.5. This grid is then divided into cells of size Dsep times Dsep, and each cell contains a list of points.

Additions can be made (without any tests!) using the AddPoint method, distance tests could be made using the Collides, SeedCollides and the (internal) TestCollision methods.

The grid is stored as an linear array of cells, each cell being an array of points. There are three coordinates systems defined over this array. One is 1D, the (integral) cell id, specifying the index into the above mentioned linear array. The second one is the 2D integer cell space, defined as [0..m_cellsX]x[0..m_cellsY], and which is mainly used for figuring out neighbouring cells. The last one is the [0.0-m_width]x[0.0-m_height],as specified in the constructor, it's actually usually a bit larger, but that doesn't change the functionality in any way.

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Constructor & Destructor Documentation

Reggrid::Reggrid	(	float	width,
		float	height,
		float	separatingDistance,
		float	testingDistance
	)

Regular grid constructor.

Parameters:

	width	The requested width of the grid (will be enlarged to a muliple of separatingDistance)
	height	The requested height of the grid (will be enlarged to a muliple of separatingDistance)
	separatingDistance	Separating distance, as defined in the paper, and also the maximum allowed distance for testing
	testingDistance	Testing distance, as defined in the paper, <= separating distance.

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Member Function Documentation

void Reggrid::AddPoint

(

const cml::vector2f &

point

)

Add a point to the reggrid, without testing for any conditions.

This basically means you can add points that wouldn't pass any of the tests.

Parameters:

point

coordinates of the point we'd like to add

bool Reggrid::AreCoordsValid

(

const cml::vector2f &

point

)

const [inline]

bool Reggrid::AreCoordsValid	(	int	x,
		int	y
	)			const

Check whether the cell coordinates are valid.

Parameters:

	x	Cell's x coordinate.
	y	Cell's y coordinate.

Returns:

true is the coordinates are valid (within the grid), false otherwise.

bool Reggrid::Collides

(

const cml::vector2f &

point

)

const

Check for collision using the intersection conditions, ie.

using the testing distance as the testing distance.

Parameters:

point

Coordinates of the point for which we want to check

vector< cml::vector2f > & Reggrid::GetCell

(

int

cellId

)

Gets a list (std::vector) of point for a given cell.

Parameters:

cellId

Id of the cell in whose list of point we're interested.

Returns:

List of point for the given cell

const vector< cml::vector2f > & Reggrid::GetCell

(

int

cellId

)

const

Gets a const list (std::vector) of point for a given cell.

Parameters:

cellId

Id of the cell in whose list of point we're interested.

Returns:

Const list of point for the given cell

int Reggrid::GetCellIDFromCellCoords	(	int	x,
		int	y
	)			const

Calculates the cell id from cell coordinates.

Parameters:

	x	Cell's x coordinate.
	y	Cell's y coordinate.

Returns:

The cell's id

int Reggrid::GetCellIDFromCoords	(	float	x,
		float	y
	)			const

Calculates the cell id from coordinates (in the space defined by the parameter's constructor).

Parameters:

	x	The coordinate, should be between 0.0 and m_width parameter, as given in the constructor.
	y	The coordinate, should be between 0.0 and m_height parameter, as given in the constructor.

Returns:

The cell's id

void Reggrid::GetCoordsFromID	(	int	cellId,
		int &	x,
		int &	y
	)			const

Calculates the cell's x,y coordinates from a cell's ID.

Parameters:

	cellId	Id of the cell whoe's coordinates we want to compute
	x	Output parameter, will contain the x coordinate
	y	Output parameter, will contain the y coordinte

float Reggrid::GetTaperingSize

(

const cml::vector2f &

point

)

const

bool Reggrid::SeedCollides

(

const cml::vector2f &

point

)

const

Check for collision using the seed conditions, ie.

using the separating distance as the testing distance.

Parameters:

point

coordinates of the point for which we want to check

bool Reggrid::TestCollision	(	const cml::vector2f &	point,
		float	distance
	)			const

Check for collision using an arbitrary distance as the testing distance.

Remarks:

This method is only guaranteed to work for distance <= separating distance!

Parameters:

	point	Coordinates of the point for which we want to check
	distance	Distance

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Member Data Documentation

int Reggrid::m_cellsX

Width of the grid, in cells.

int Reggrid::m_cellsY

Height of the grid, in cells.

vector<cml::vector2f>* Reggrid::m_grid

The grid itself.

float Reggrid::m_height

Actual height of the grid, ie. a multiple of m_separatingDistance.

float Reggrid::m_separatingDistance

Separating distance, as defined in the paper.

float Reggrid::m_testingDistance

Testing distance, as defined in the paper, always <= separating distance.

float Reggrid::m_width

Actual width of the grid, ie. a multiple of m_separatingDistance.

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

• C:/Documents and Settings/benesova/Plocha/FlowVis/vislab2/reggrid.h
• C:/Documents and Settings/benesova/Plocha/FlowVis/vislab2/reggrid.cpp