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vtkOBBTree Class Reference

generate oriented bounding box (OBB) tree. More...

#include <vtkOBBTree.h>

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List of all members.

Public Methods

virtual const char * GetClassName ()
virtual int IsA (const char *type)
void ComputeOBB (vtkPoints *pts, float corner[3], float max[3], float mid[3], float min[3], float size[3])
void ComputeOBB (vtkDataSet *input, float corner[3], float max[3], float mid[3], float min[3], float size[3])
int IntersectWithLine (float a0[3], float a1[3], float tol, float &t, float x[3], float pcoords[3], int &subId)
int IntersectWithLine (float a0[3], float a1[3], float tol, float &t, float x[3], float pcoords[3], int &subId, int &cellId)
int IntersectWithLine (float a0[3], float a1[3], float tol, float &t, float x[3], float pcoords[3], int &subId, int &cellId, vtkGenericCell *cell)
int DisjointOBBNodes (vtkOBBNode *nodeA, vtkOBBNode *nodeB, vtkMatrix4x4 *XformBtoA)
int LineIntersectsNode (vtkOBBNode *pA, float B0[3], float B1[3])
int TriangleIntersectsNode (vtkOBBNode *pA, float p0[3], float p1[3], float 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 ()
void GenerateRepresentation (int level, vtkPolyData *pd)

Static Public Methods

int IsTypeOf (const char *type)
vtkOBBTree * SafeDownCast (vtkObject *o)
vtkOBBTree * New ()

Protected Methods

 vtkOBBTree ()
 ~vtkOBBTree ()
 vtkOBBTree (const vtkOBBTree &)
void operator= (const vtkOBBTree &)
void ComputeOBB (vtkIdList *cells, float corner[3], float max[3], float mid[3], float min[3], float 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

Detailed Description

generate oriented bounding box (OBB) tree.

Date:
2000/12/10 20:08:44
Revision:
1.31
Thanks:
Thanks to Peter C. Everett <pce@world.std.com> for improvements and enhancements to vtkOBBTree class.
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.
Warning:
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 vtkLocatorFilter
Examples:
vtkOBBTree (examples)

Definition at line 111 of file vtkOBBTree.h.


Constructor & Destructor Documentation

vtkOBBTree::vtkOBBTree   [protected]
 

vtkOBBTree::~vtkOBBTree   [protected]
 

vtkOBBTree::vtkOBBTree const vtkOBBTree &    [inline, protected]
 

Definition at line 187 of file vtkOBBTree.h.


Member Function Documentation

virtual const char* vtkOBBTree::GetClassName   [virtual]
 

Return the class name as a string. This method is defined in all subclasses of vtkObject with the vtkTypeMacro found in vtkSetGet.h.

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 vtkTypeMacro 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 vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkCellLocator.

vtkOBBTree* vtkOBBTree::SafeDownCast vtkObject   o [static]
 

Will cast the supplied object to vtkObject* is this is a safe operation (i.e., a safe downcast); otherwise NULL is returned. This method is defined in all subclasses of vtkObject with the vtkTypeMacro found in vtkSetGet.h.

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,
float    corner[3],
float    max[3],
float    mid[3],
float    min[3],
float    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,
float    corner[3],
float    max[3],
float    mid[3],
float    min[3],
float    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::IntersectWithLine float    a0[3],
float    a1[3],
float    tol,
float &    t,
float    x[3],
float    pcoords[3],
int &    subId
[virtual]
 

Return intersection point (if any) of finite line with cells contained in cell locator.

Reimplemented from vtkCellLocator.

int vtkOBBTree::IntersectWithLine float    a0[3],
float    a1[3],
float    tol,
float &    t,
float    x[3],
float    pcoords[3],
int &    subId,
int &    cellId
[virtual]
 

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

Reimplemented from vtkCellLocator.

int vtkOBBTree::IntersectWithLine float    a0[3],
float    a1[3],
float    tol,
float &    t,
float    x[3],
float    pcoords[3],
int &    subId,
int &    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 BTX

int vtkOBBTree::LineIntersectsNode vtkOBBNode   pA,
float    B0[3],
float    B1[3]
 

Returns true if line intersects node.

int vtkOBBTree::TriangleIntersectsNode vtkOBBNode   pA,
float    p0[3],
float    p1[3],
float    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]
 

Build the locator from the input dataset.

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::operator= const vtkOBBTree &    [inline, protected]
 

Definition at line 188 of file vtkOBBTree.h.

void vtkOBBTree::ComputeOBB vtkIdList   cells,
float    corner[3],
float    max[3],
float    mid[3],
float    min[3],
float    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 196 of file vtkOBBTree.h.

vtkPoints* vtkOBBTree::PointsList [protected]
 

Definition at line 198 of file vtkOBBTree.h.

int* vtkOBBTree::InsertedPoints [protected]
 

Definition at line 199 of file vtkOBBTree.h.

int vtkOBBTree::OBBCount [protected]
 

Definition at line 200 of file vtkOBBTree.h.

int vtkOBBTree::DeepestLevel [protected]
 

Definition at line 201 of file vtkOBBTree.h.


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