vtkOBBTree Class Reference

#include <vtkOBBTree.h>

Inheritance diagram for vtkOBBTree:

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Collaboration diagram for vtkOBBTree:

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List of all members.

Detailed Description

generate oriented bounding box (OBB) tree

vtkOBBTree is an object to generate oriented bounding box (OBB) trees. An oriented bounding box is a bounding box that does not necessarily line up along coordinate axes. The OBB tree is a hierarchical tree structure of such boxes, where deeper levels of OBB confine smaller regions of space.

To build the OBB, a recursive, top-down process is used. First, the root OBB is constructed by finding the mean and covariance matrix of the cells (and their points) that define the dataset. The eigenvectors of the covariance matrix are extracted, giving a set of three orthogonal vectors that define the tightest-fitting OBB. To create the two children OBB's, a split plane is found that (approximately) divides the number cells in half. These are then assigned to the children OBB's. This process then continues until the MaxLevel ivar limits the recursion, or no split plane can be found.

A good reference for OBB-trees is Gottschalk & Manocha in Proceedings of Siggraph `96.

Warning:: Since this algorithms works from a list of cells, the OBB tree will only bound the "geometry" attached to the cells if the convex hull of the cells bounds the geometry.
Long, skinny cells (i.e., cells with poor aspect ratio) may cause unsatisfactory results. This is due to the fact that this is a top-down implementation of the OBB tree, requiring that one or more complete cells are contained in each OBB. This requirement makes it hard to find good split planes during the recursion process. A bottom-up implementation would go a long way to correcting this problem.

See also:: vtkLocator vtkCellLocator vtkPointLocator

Tests:: vtkOBBTree (Tests)

Definition at line 82 of file vtkOBBTree.h.


Public Types
typedef vtkCellLocator	Superclass
Public Member Functions
virtual const char *	GetClassName ()
virtual int	IsA (const char *type)
void	PrintSelf (ostream &os, vtkIndent indent)
int	InsideOrOutside (const double point[3])
int	IntersectWithLine (double a0[3], double a1[3], double tol, double &t, double x[3], double pcoords[3], int &subId, vtkIdType &cellId)
int	IntersectWithLine (double a0[3], double a1[3], double tol, double &t, double x[3], double pcoords[3], int &subId, vtkIdType &cellId, vtkGenericCell *cell)
int	LineIntersectsNode (vtkOBBNode *pA, double b0[3], double b1[3])
void	GenerateRepresentation (int level, vtkPolyData *pd)

void	ComputeOBB (vtkPoints *pts, double corner[3], double max[3], double mid[3], double min[3], double size[3])

void	ComputeOBB (vtkDataSet *input, double corner[3], double max[3], double mid[3], double min[3], double size[3])

int	IntersectWithLine (const double a0[3], const double a1[3], vtkPoints points, vtkIdList cellIds)

int	IntersectWithLine (double a0[3], double a1[3], double tol, double &t, double x[3], double pcoords[3], int &subId)

int	DisjointOBBNodes (vtkOBBNode nodeA, vtkOBBNode nodeB, vtkMatrix4x4 *XformBtoA)

int	TriangleIntersectsNode (vtkOBBNode pA, double p0[3], double p1[3], double p2[3], vtkMatrix4x4 XformBtoA)

int	IntersectWithOBBTree (vtkOBBTree OBBTreeB, vtkMatrix4x4 XformBtoA, int(function)(vtkOBBNode nodeA, vtkOBBNode nodeB, vtkMatrix4x4 Xform, void arg), void data_arg)

void	FreeSearchStructure ()
void	BuildLocator ()
Static Public Member Functions
static int	IsTypeOf (const char *type)
static vtkOBBTree *	SafeDownCast (vtkObject *o)
static vtkOBBTree *	New ()
Protected Member Functions
	vtkOBBTree ()
	~vtkOBBTree ()
void	ComputeOBB (vtkIdList *cells, double corner[3], double max[3], double mid[3], double min[3], double size[3])
void	BuildTree (vtkIdList cells, vtkOBBNode parent, int level)
void	DeleteTree (vtkOBBNode *OBBptr)
void	GeneratePolygons (vtkOBBNode OBBptr, int level, int repLevel, vtkPoints pts, vtkCellArray *polys)
Protected Attributes
vtkOBBNode *	Tree
vtkPoints *	PointsList
int *	InsertedPoints
int	OBBCount
int	DeepestLevel

Member Typedef Documentation

typedef vtkCellLocator vtkOBBTree::Superclass

Reimplemented from vtkCellLocator.

Definition at line 85 of file vtkOBBTree.h.

Constructor & Destructor Documentation

vtkOBBTree::vtkOBBTree ( ) [protected]

vtkOBBTree::~vtkOBBTree ( ) [protected]

Member Function Documentation

virtual const char* vtkOBBTree::GetClassName ( ) [virtual]

Reimplemented from vtkCellLocator.

static int vtkOBBTree::IsTypeOf ( const char * name ) [static]

Return 1 if this class type is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.

Reimplemented from vtkCellLocator.

virtual int vtkOBBTree::IsA ( const char * name ) [virtual]

Return 1 if this class is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.

Reimplemented from vtkCellLocator.

static vtkOBBTree* vtkOBBTree::SafeDownCast ( vtkObject * o ) [static]

Reimplemented from vtkCellLocator.

void vtkOBBTree::PrintSelf	(	ostream &	os,
		vtkIndent	indent
	)			`[virtual]`

Methods invoked by print to print information about the object including superclasses. Typically not called by the user (use Print() instead) but used in the hierarchical print process to combine the output of several classes.

Reimplemented from vtkCellLocator.

static vtkOBBTree* vtkOBBTree::New ( ) [static]

Construct with automatic computation of divisions, averaging 25 cells per octant.

Reimplemented from vtkCellLocator.

void vtkOBBTree::ComputeOBB	(	vtkPoints *	pts,
		double	corner[3],
		double	max[3],
		double	mid[3],
		double	min[3],
		double	size[3]
	)

Compute an OBB from the list of points given. Return the corner point and the three axes defining the orientation of the OBB. Also return a sorted list of relative "sizes" of axes for comparison purposes.

void vtkOBBTree::ComputeOBB	(	vtkDataSet *	input,
		double	corner[3],
		double	max[3],
		double	mid[3],
		double	min[3],
		double	size[3]
	)

Compute an OBB for the input dataset using the cells in the data. Return the corner point and the three axes defining the orientation of the OBB. Also return a sorted list of relative "sizes" of axes for comparison purposes.

int vtkOBBTree::InsideOrOutside ( const double point[3] )

Determine whether a point is inside or outside the data used to build this OBB tree. The data must be a closed surface vtkPolyData data set. The return value is +1 if outside, -1 if inside, and 0 if undecided.

int vtkOBBTree::IntersectWithLine	(	const double	a0[3],
		const double	a1[3],
		vtkPoints *	points,
		vtkIdList *	cellIds
	)

Take the passed line segment and intersect it with the data set. This method assumes that the data set is a vtkPolyData that describes a closed surface, and the intersection points that are returned in 'points' alternate between entrance points and exit points. The return value of the function is 0 if no intersections were found, -1 if point 'a0' lies inside the closed surface, or +1 if point 'a0' lies outside the closed surface. Either 'points' or 'cellIds' can be set to NULL if you don't want to receive that information.

int vtkOBBTree::IntersectWithLine	(	double	a0[3],
		double	a1[3],
		double	tol,
		double &	t,
		double	x[3],
		double	pcoords[3],
		int &	subId
	)			`[virtual]`

Return the first intersection of the specified line segment with the OBB tree, as well as information about the cell which the line segment intersected.

Reimplemented from vtkCellLocator.

int vtkOBBTree::IntersectWithLine	(	double	a0[3],
		double	a1[3],
		double	tol,
		double &	t,
		double	x[3],
		double	pcoords[3],
		int &	subId,
		vtkIdType &	cellId
	)			`[virtual]`

Return intersection point (if any) AND the cell which was intersected by the finite line.

Reimplemented from vtkCellLocator.

int vtkOBBTree::IntersectWithLine	(	double	a0[3],
		double	a1[3],
		double	tol,
		double &	t,
		double	x[3],
		double	pcoords[3],
		int &	subId,
		vtkIdType &	cellId,
		vtkGenericCell *	cell
	)			`[virtual]`

Return intersection point (if any) AND the cell which was intersected by the finite line. The cell is returned as a cell id and as a generic cell.

Reimplemented from vtkCellLocator.

int vtkOBBTree::DisjointOBBNodes	(	vtkOBBNode *	nodeA,
		vtkOBBNode *	nodeB,
		vtkMatrix4x4 *	XformBtoA
	)

Returns true if nodeB and nodeA are disjoint after optional transformation of nodeB with matrix XformBtoA

int vtkOBBTree::LineIntersectsNode	(	vtkOBBNode *	pA,
		double	b0[3],
		double	b1[3]
	)

Returns true if line intersects node.

int vtkOBBTree::TriangleIntersectsNode	(	vtkOBBNode *	pA,
		double	p0[3],
		double	p1[3],
		double	p2[3],
		vtkMatrix4x4 *	XformBtoA
	)

Returns true if triangle (optionally transformed) intersects node.

int vtkOBBTree::IntersectWithOBBTree	(	vtkOBBTree *	OBBTreeB,
		vtkMatrix4x4 *	XformBtoA,
		int()(vtkOBBNode nodeA, vtkOBBNode nodeB, vtkMatrix4x4 Xform, void *arg)	function,
		void *	data_arg
	)

For each intersecting leaf node pair, call function. OBBTreeB is optionally transformed by XformBtoA before testing.

void vtkOBBTree::FreeSearchStructure ( ) [virtual]

Satisfy locator's abstract interface, see vtkLocator.

Reimplemented from vtkCellLocator.

void vtkOBBTree::BuildLocator ( ) [virtual]

Satisfy locator's abstract interface, see vtkLocator.

Reimplemented from vtkCellLocator.

void vtkOBBTree::GenerateRepresentation	(	int	level,
		vtkPolyData *	pd
	)			`[virtual]`

Create polygonal representation for OBB tree at specified level. If level < 0, then the leaf OBB nodes will be gathered. The aspect ratio (ar) and line diameter (d) are used to control the building of the representation. If a OBB node edge ratio's are greater than ar, then the dimension of the OBB is collapsed (OBB->plane->line). A "line" OBB will be represented either as two crossed polygons, or as a line, depending on the relative diameter of the OBB compared to the diameter (d).

Reimplemented from vtkCellLocator.

void vtkOBBTree::ComputeOBB	(	vtkIdList *	cells,
		double	corner[3],
		double	max[3],
		double	mid[3],
		double	min[3],
		double	size[3]
	)			`[protected]`

void vtkOBBTree::BuildTree	(	vtkIdList *	cells,
		vtkOBBNode *	parent,
		int	level
	)			`[protected]`

void vtkOBBTree::DeleteTree ( vtkOBBNode * OBBptr ) [protected]

void vtkOBBTree::GeneratePolygons	(	vtkOBBNode *	OBBptr,
		int	level,
		int	repLevel,
		vtkPoints *	pts,
		vtkCellArray *	polys
	)			`[protected]`

Member Data Documentation

vtkOBBNode* vtkOBBTree::Tree [protected]

Reimplemented from vtkCellLocator.

Definition at line 203 of file vtkOBBTree.h.

vtkPoints* vtkOBBTree::PointsList [protected]

Definition at line 205 of file vtkOBBTree.h.

int* vtkOBBTree::InsertedPoints [protected]

Definition at line 206 of file vtkOBBTree.h.

int vtkOBBTree::OBBCount [protected]

Definition at line 207 of file vtkOBBTree.h.

int vtkOBBTree::DeepestLevel [protected]

Definition at line 208 of file vtkOBBTree.h.

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

dox/Graphics/vtkOBBTree.h

vtkOBBTree Class Reference

Detailed Description

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation