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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
Created by:
  • Schroeder, Will
CVS contributions (if > 5%):
  • Schroeder, Will (32%)
  • Warfield, Simon (24%)
  • Gobbi, David (19%)
  • Martin, Ken (6%)
CVS logs (CVSweb):
  • .h (/Graphics/vtkOBBTree.h)
  • .cxx (/Graphics/vtkOBBTree.cxx)
Tests:
vtkOBBTree (Tests)

Definition at line 95 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

int IsTypeOf (const char *type)
vtkOBBTreeSafeDownCast (vtkObject *o)
vtkOBBTreeNew ()

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

vtkOBBNodeTree
vtkPointsPointsList
int * InsertedPoints
int OBBCount
int DeepestLevel


Member Typedef Documentation

typedef vtkCellLocator vtkOBBTree::Superclass
 

Reimplemented from vtkCellLocator.

Definition at line 98 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.

int vtkOBBTree::IsTypeOf const char *  type  )  [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 *  type  )  [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.

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.

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(*  function)(vtkOBBNode *nodeA, vtkOBBNode *nodeB, vtkMatrix4x4 *Xform, void *arg),
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 216 of file vtkOBBTree.h.

vtkPoints* vtkOBBTree::PointsList [protected]
 

Definition at line 218 of file vtkOBBTree.h.

int* vtkOBBTree::InsertedPoints [protected]
 

Definition at line 219 of file vtkOBBTree.h.

int vtkOBBTree::OBBCount [protected]
 

Definition at line 220 of file vtkOBBTree.h.

int vtkOBBTree::DeepestLevel [protected]
 

Definition at line 221 of file vtkOBBTree.h.


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