dlr::numeric::AmanatidesWoo2D< ARRAY2D > Class Template Reference

This class implements the Fast Voxel Traversal Algorithm of Amanatides and Woo [Ref] for 2D arrays. More...

#include <amanatidesWoo2D.h>

List of all members.

Public Types

typedef
AmanatidesWoo2DIterator
< ARRAY2D > iterator

This typedef specifies the type which will be returned by member functions begin() and end().

Public Member Functions

AmanatidesWoo2D (ARRAY2D &data, const Transform2D &pixelTworld, const Vector2D &rayOrigin, const Vector2D &rayDirection, bool downstreamOnly=true)

This constructor specifies all of the internal state of the AmanatidesWoo2D class.

AmanatidesWoo2D (const AmanatidesWoo2D &source)

This is the copy constructor.

~AmanatidesWoo2D ()

This is the destructor.

iterator begin ()

This member function returns an iterator which references the first pixel along the traced ray.

iterator end ()

This member function returns an iterator which references an invalid pixel, and which will be equal (==) to the iterator returned by member function begin() when that iterator has fully traversed the line of pixels.

ARRAY2D & getData ()

This member function returns a reference to the array object over which iteration is performed.

bool validIntersection ()

This member function returns true if the iterator returned by member function begin() will point to a valid pixel.

AmanatidesWoo2D & operator= (const AmanatidesWoo2D &source)

The assignment operator copies its argument.

Detailed Description

template<class ARRAY2D>
class dlr::numeric::AmanatidesWoo2D< ARRAY2D >

This class implements the Fast Voxel Traversal Algorithm of Amanatides and Woo [Ref] for 2D arrays.

The algorithm is for efficient ray tracing through regular grids. For convenience, there are two coordinate systems associated with this class:

The pixel coordinate system is an integer-based coordinate system associated with the array.

The world coordinate system, which can differ from the pixel coordinate system only by translation, rotation, and non-isotropic scaling, but is in other respects arbitrary.

The pixel coordinate system has its origin at the corner of the 2D array, has its first coordinate (which we'll call U) parallel to the rows of the array, and has its second coordinate (which we'll call V) parallel to the columns of the array. As you move along any row of the 2D array, the transition from the first column to the second occurs at U == 1.0, the transition from the second column to the third occurs at U == 2.0, and so on. Similarly as you move along any column of the array, the transition from the first row to the second occurs at V == 1.0, and the transition from the second row to the third occurs at V == 2.0.

Once constructed, you can use the AmanatidesWoo2D class to access pixels along a straight line through the 2D array using STL-style iteration. That is, the member functions AmanatidesWoo2D::begin() returns an iterator which references subsequent pixels along the line, and will become equal (==) to the iterator returned by AmanatidesWoo2D::end() when the line passes out of the 2D array. Here's an example usage, which will probably format terribly in the Doxygen-generated doc:

typedef AmanatidesWoo2D< Array2D<int> >iterator awIterator;

AmanatidesWoo2D< Array2D<int> > rayTracer( myArray2D, rayOrigin, rayDirection, false);

awIterator iterator0 = rayTracer.begin();

awIterator iterator1 = rayTracer.end();

for(; iterator0 != iterator1; ++iterator0) {

*iterator0 = 0;

}

Definition at line 80 of file amanatidesWoo2D.h.

Member Typedef Documentation

template<class ARRAY2D >

typedef AmanatidesWoo2DIterator<ARRAY2D> dlr::numeric::AmanatidesWoo2D< ARRAY2D >::iterator

This typedef specifies the type which will be returned by member functions begin() and end().

AmanatidesWoo2DIterator is a forward iterator, and has unusual semantics for operator==(). Be sure to understand them before using this class.

Definition at line 91 of file amanatidesWoo2D.h.

Constructor & Destructor Documentation

template<class ARRAY2D >

dlr::numeric::AmanatidesWoo2D< ARRAY2D >::AmanatidesWoo2D	(	ARRAY2D &	data,
		const Transform2D &	pixelTworld,
		const Vector2D &	rayOrigin,
		const Vector2D &	rayDirection,
		bool	downstreamOnly = `true`
	)			`[inline]`

This constructor specifies all of the internal state of the AmanatidesWoo2D class.

After construction, the AmanatidesWoo2D instance is ready to be used.

Parameters:

	data	This argument specifies the 2D array over which to iterate.
	pixelTworld	This parameter specifies a coordinate transformation which takes world coordinates and converts them into pixel coordinates.
	rayOrigin	This parameter specifies the starting point of the ray to be traced, expressed in world coordinates. If you'd rather express rayOrigin and rayDirection in pixel coordinates, simply set argument pixelTworld to the identity transform. Note that rayOrigin does not have to lie inside the pixel array.
	rayDirection	This parameter specifies the direction of the ray to be traced, expressed in world coordinates. In other words, any point on the line of interest can be written as (rayOrigin + t * rayDirection) for some value of t. If you'd rather express rayOrigin and rayDirection in pixel coordinates, simply set argument pixelTworld to the identity transform.
	downstreamOnly	This boolean argument specifies whether pixels "upstream" of rayOrigin are to be included in the pixel traversal. If downstreamOnly is set to false, pixels which intersect the line (rayOrigin + t * rayDirection) will be included in the iteration even if they intersect the line at negative values of t.

Definition at line 344 of file amanatidesWoo2D.h.

References dlr::numeric::Vector2D::x(), and dlr::numeric::Vector2D::y().

template<class ARRAY2D >

dlr::numeric::AmanatidesWoo2D< ARRAY2D >::AmanatidesWoo2D ( const AmanatidesWoo2D< ARRAY2D > & source ) [inline]

This is the copy constructor.

After copying, the new AmanatidesWoo2D instance and the copied instance both reference the same pixel array.

Parameters:

source

The AmanatidesWoo2D instance to be copied.

Definition at line 477 of file amanatidesWoo2D.h.

template<class ARRAY2D >

dlr::numeric::AmanatidesWoo2D< ARRAY2D >::~AmanatidesWoo2D ( ) [inline]

This is the destructor.

It destroys the AmanatidesWoo2D instance and cleans up any allocated memory.

Definition at line 495 of file amanatidesWoo2D.h.

Member Function Documentation

template<class ARRAY2D >

AmanatidesWoo2D< ARRAY2D >::iterator dlr::numeric::AmanatidesWoo2D< ARRAY2D >::begin ( ) [inline]

This member function returns an iterator which references the first pixel along the traced ray.

If constructor argument downstreamOnly was set to false, this iterator will either point to a pixel on the very edge of the array, or (in the case that the ray does not intersect the pixel array) be equal to this->end(). If constructor argument downstreamOnly was set to true, then this iterator will point to an edge pixel, or point to an interior pixel (in the case that rayOrigin lies within the boundaries of the pixel array), or be equal to this->end() (in the case that the ray does not intersect the pixel array, and in the case that rayOrigin lies outside the pixel array and rayDirection points away from the pixel array).

Returns:: The return value is an iterator pointing to the first pixel in the array, or else an iterator for which (iter == this->end()) is true.

Definition at line 500 of file amanatidesWoo2D.h.

template<class ARRAY2D >

AmanatidesWoo2D< ARRAY2D >::iterator dlr::numeric::AmanatidesWoo2D< ARRAY2D >::end ( ) [inline]

This member function returns an iterator which references an invalid pixel, and which will be equal (==) to the iterator returned by member function begin() when that iterator has fully traversed the line of pixels.

Returns:: The return value is an iterator pointing to an invalid pixel, for use as the end iterator in the comparison clause of a loop: "while(rayIterator != endIterator) {++rayIterator; ...;}".

Definition at line 510 of file amanatidesWoo2D.h.

template<class ARRAY2D >

ARRAY2D& dlr::numeric::AmanatidesWoo2D< ARRAY2D >::getData ( ) [inline]

This member function returns a reference to the array object over which iteration is performed.

Returns:: The return value is a reference to the data array.

Definition at line 196 of file amanatidesWoo2D.h.

template<class ARRAY2D >

AmanatidesWoo2D< ARRAY2D > & dlr::numeric::AmanatidesWoo2D< ARRAY2D >::operator= ( const AmanatidesWoo2D< ARRAY2D > & source ) [inline]

The assignment operator copies its argument.

After copying, *this and the copied instance both reference the same pixel array.

Parameters:

source

The AmanatidesWoo2D instance to be copied.

Returns:: The return value is a reference to *this.

Definition at line 532 of file amanatidesWoo2D.h.

template<class ARRAY2D >

bool dlr::numeric::AmanatidesWoo2D< ARRAY2D >::validIntersection ( ) [inline]

This member function returns true if the iterator returned by member function begin() will point to a valid pixel.

In other words, if constructor argument downstreamOnly was set to false, the return value of validIntersection() indicates whether the ray specified in the constructor actually intersects the pixel array. If constructor argument downstreamOnly was set to true, the return value of validIntersection whether the "downstream" half of the ray actually intersects the pixel array.

Returns:: A boolean indicating whether or not (this->begin() == this->end()) will be true.

Definition at line 524 of file amanatidesWoo2D.h.

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

amanatidesWoo2D.h


Public Types
typedef AmanatidesWoo2DIterator < ARRAY2D >	iterator
	This typedef specifies the type which will be returned by member functions begin() and end().
Public Member Functions
	AmanatidesWoo2D (ARRAY2D &data, const Transform2D &pixelTworld, const Vector2D &rayOrigin, const Vector2D &rayDirection, bool downstreamOnly=true)
	This constructor specifies all of the internal state of the AmanatidesWoo2D class.
	AmanatidesWoo2D (const AmanatidesWoo2D &source)
	This is the copy constructor.
	~AmanatidesWoo2D ()
	This is the destructor.
iterator	begin ()
	This member function returns an iterator which references the first pixel along the traced ray.
iterator	end ()
	This member function returns an iterator which references an invalid pixel, and which will be equal (==) to the iterator returned by member function begin() when that iterator has fully traversed the line of pixels.
ARRAY2D &	getData ()
	This member function returns a reference to the array object over which iteration is performed.
bool	validIntersection ()
	This member function returns true if the iterator returned by member function begin() will point to a valid pixel.
AmanatidesWoo2D &	operator= (const AmanatidesWoo2D &source)
	The assignment operator copies its argument.

dlr::numeric::AmanatidesWoo2D< ARRAY2D > Class Template Reference

Public Types

Public Member Functions

Detailed Description

template<class ARRAY2D> class dlr::numeric::AmanatidesWoo2D< ARRAY2D >

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

template<class ARRAY2D>
class dlr::numeric::AmanatidesWoo2D< ARRAY2D >