# BVH_BaseTraverse< MetricType > Class Template Reference

The classes implement the traverse of the BVH tree. More...

`#include <BVH_Traverse.hxx>`

Inheritance diagram for BVH_BaseTraverse< MetricType >:
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## Public Member Functions

Metrics comparison for choosing the best branch
virtual Standard_Boolean IsMetricBetter (const MetricType &, const MetricType &) const
Compares the two metrics and chooses the best one. Returns true if the first metric is better than the second, false otherwise. More...

Rejection of the node by metric
virtual Standard_Boolean RejectMetric (const MetricType &) const
Rejects the node by the metric. More...

Condition to stop the descend
virtual Standard_Boolean Stop () const
Returns the flag controlling the tree descend. Returns true if the tree descend should be stopped. More...

## Protected Member Functions

Constructors
BVH_BaseTraverse ()
Constructor. More...

virtual ~BVH_BaseTraverse ()
Destructor. More...

## Detailed Description

### template<class MetricType> class BVH_BaseTraverse< MetricType >

The classes implement the traverse of the BVH tree.

There are two traverse methods implemented:

• Traverse of the single tree
• Parallel traverse of two trees

To perform Selection of the elements from BVH_Tree using the traverse methods implemented here it is required to define Acceptance/Rejection rules in the following methods:

• RejectNode - Node rejection by its bounding box. It is applied to both inner and outer nodes of the BVH tree. Optionally, the method should compute the metric for the node which will allow performing traverse faster by descending by the best branches.
• Accept - Element acceptance. It takes the index of the element of BVH tree. The access to the element itself should be performed through the set on which BVH is built. The Accept method implements the leaf node operation and usually defines the logic of the whole operation.
• IsMetricBetter - Compares the metrics of the nodes and returns true if the left metric is better than the right one.
• RejectMetric - Node rejection by the metric. It should compare the metric of the node with the global one and return true if the global metric is better than the given one.
• Stop - implements conditions to stop the tree descend if the necessary elements are already found.

The selector of a single tree has an extra method which allows accepting the whole branches without any further checks (e.g. full inclusion test):

• AcceptMetric - basing on the metric of the node decides if the node may be accepted without any further checks.

Two ways of selection are possible:

1. Set the BVH set containing the tree and use the method Select() which allows using common interface for setting the BVH Set for accessing the BVH tree and elements in the Accept method.
2. Keep the BVHSetType void, do not set the BVH set and use the method Select (const BVH_Tree<>&) which allows performing selection on the arbitrary BVH tree.

Here is the example of usage of the traverse to find the point-triangulation minimal distance.

// Structure to contain points of the triangle
struct Triangle
{
Triangle() {}
Triangle(const BVH_Vec3d& theNode1,
const BVH_Vec3d& theNode2,
const BVH_Vec3d& theNode3)
: Node1 (theNode1), Node2 (theNode2), Node3 (theNode3)
{}
BVH_Vec3d Node1;
BVH_Vec3d Node2;
BVH_Vec3d Node3;
};
// Selector for min point-triangulation distance
class BVH_PointTriangulationSqDist :
public BVH_Distance<Standard_Real, 3, BVH_Vec3d, BVH_BoxSet<Standard_Real, 3, Triangle>>
{
public:
// Computes the distance from the point to bounding box
virtual Standard_Boolean RejectNode (const BVH_Vec3d& theCMin,
const BVH_Vec3d& theCMax,
Standard_Real& theDistance) const Standard_OVERRIDE
{
theDistance = BVH_Tools<Standard_Real, 3>::PointBoxSquareDistance (myObject, theCMin, theCMax);
return RejectMetric (theDistance);
}
// Computes the distance from the point to triangle
virtual Standard_Boolean Accept (const Standard_Integer theIndex,
{
const Triangle& aTri = myBVHSet->Element (theIndex);
Standard_Real aDist = BVH_Tools<Standard_Real, 3>::PointTriangleSquareDistance (myObject, aTri.Node1, aTri.Node2, aTri.Node3);
{
return Standard_True;
}
}
};
// Point to which the distance is required
BVH_Vec3d aPoint = ...;
// BVH Set containing triangulation
{
}
BVH::VectorType< Standard_Real, 3 >::Type BVH_Vec3d
3D vector of double precision reals.
Definition: BVH_Types.hxx:150
#define Standard_OVERRIDE
Should be used in declarations of virtual methods overridden in the derived classes,...
Definition: Standard_Macro.hxx:41
bool Standard_Boolean
Definition: Standard_TypeDef.hxx:64
#define Standard_False
Definition: Standard_TypeDef.hxx:56
int Standard_Integer
Definition: Standard_TypeDef.hxx:61
#define Standard_True
Definition: Standard_TypeDef.hxx:57
double Standard_Real
Definition: Standard_TypeDef.hxx:63
virtual Standard_Boolean RejectMetric(const MetricType &) const
Rejects the node by the metric.
Definition: BVH_Traverse.hxx:151
Abstract class for computation of the min distance between some Object and elements of BVH tree....
Definition: BVH_Distance.hxx:33
static T PointTriangleSquareDistance(const BVH_VecNt &thePoint, const BVH_VecNt &theNode0, const BVH_VecNt &theNode1, const BVH_VecNt &theNode2)
Computes square distance between point and triangle.
Definition: BVH_Tools.hxx:239
static T PointBoxSquareDistance(const BVH_VecNt &thePoint, const BVH_Box< T, N > &theBox)
Computes square distance between point and bounding box.
Definition: BVH_Tools.hxx:74
Intrusive smart pointer for use with Standard_Transient class and its descendants.
Definition: Standard_Handle.hxx:52
T * get() const
STL-like cast to pointer to referred object (note non-const).
Definition: Standard_Handle.hxx:124

Abstract class implementing the base Traverse interface required for selection of the elements from BVH tree.

Template Parameters
 MetricType Type of metric to perform more optimal tree descend

## ◆ BVH_BaseTraverse()

template<class MetricType >
 BVH_BaseTraverse< MetricType >::BVH_BaseTraverse ( )
inlineprotected

Constructor.

## ◆ ~BVH_BaseTraverse()

template<class MetricType >
 virtual BVH_BaseTraverse< MetricType >::~BVH_BaseTraverse ( )
inlineprotectedvirtual

Destructor.

## ◆ IsMetricBetter()

template<class MetricType >
 virtual Standard_Boolean BVH_BaseTraverse< MetricType >::IsMetricBetter ( const MetricType & , const MetricType & ) const
inlinevirtual

Compares the two metrics and chooses the best one. Returns true if the first metric is better than the second, false otherwise.

## ◆ RejectMetric()

template<class MetricType >
 virtual Standard_Boolean BVH_BaseTraverse< MetricType >::RejectMetric ( const MetricType & ) const
inlinevirtual

Rejects the node by the metric.

## ◆ Stop()

template<class MetricType >
 virtual Standard_Boolean BVH_BaseTraverse< MetricType >::Stop ( ) const
inlinevirtual

Returns the flag controlling the tree descend. Returns true if the tree descend should be stopped.

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