org.openscience.cdk.graph.rebond

## Class Bspt

• ```public final class Bspt
extends Object```
BSP-Tree stands for Binary Space Partitioning Tree. The tree partitions n-dimensional space (in our case 3) into little boxes, facilitating searches for things which are *nearby*. For some useful background info, search the web for "bsp tree faq". Our application is somewhat simpler because we are storing points instead of polygons.

We are working with three dimensions. For the purposes of the Bspt code these dimensions are stored as 0, 1, or 2. Each node of the tree splits along the next dimension, wrapping around to 0.

```    mySplitDimension = (parentSplitDimension + 1) % 3;
```
A split value is stored in the node. Values which are ≤ splitValue are stored down the left branch. Values which are ≥ splitValue are stored down the right branch. When this happens, the search must proceed down both branches. Planar and crystalline substructures can generate values which are == along one dimension.

To get a good picture in your head, first think about it in one dimension, points on a number line. The tree just partitions the points. Now think about 2 dimensions. The first node of the tree splits the plane into two rectangles along the x dimension. The second level of the tree splits the subplanes (independently) along the y dimension into smaller rectangles. The third level splits along the x dimension. In three dimensions, we are doing the same thing, only working with 3-d boxes.

Three enumerators are provided

• enumNear(Bspt.Tuple center, double distance)
returns all the points contained in of all the boxes which are within distance from the center.
• enumSphere(Bspt.Tuple center, double distance)
returns all the points which are contained within the sphere (inclusive) defined by center + distance
• enumHemiSphere(Bspt.Tuple center, double distance)
same as sphere, but only the points which are greater along the x dimension
Author:
Miguel Howard
Source code:
master
Belongs to CDK module:
standard
Keywords:
rebonding, Binary Space Partitioning Tree, join-the-dots
Created on:
2003-05
• ### Nested Class Summary

Nested Classes
Modifier and Type Class and Description
`static interface ` `Bspt.Tuple`
• ### Constructor Summary

Constructors
Constructor and Description
`Bspt(int dimMax)`
• ### Method Summary

All Methods
Modifier and Type Method and Description
`void` `addTuple(Bspt.Tuple tuple)`
`protected void` `dump()`
`protected Enumeration` `enumeration()`
`protected org.openscience.cdk.graph.rebond.Bspt.EnumerateSphere` ```enumHemiSphere(Bspt.Tuple center, double distance)```
`protected Enumeration` ```enumNear(Bspt.Tuple center, double distance)```
`protected org.openscience.cdk.graph.rebond.Bspt.EnumerateSphere` ```enumSphere(Bspt.Tuple center, double distance)```
`String` `toString()`
• ### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`
• ### Constructor Detail

• #### Bspt

`public Bspt(int dimMax)`
• ### Method Detail

• #### addTuple

`public void addTuple(Bspt.Tuple tuple)`
• #### toString

`public String toString()`
Overrides:
`toString` in class `Object`
• #### dump

`protected void dump()`
• #### enumeration

`protected Enumeration enumeration()`
• #### enumNear

```protected Enumeration enumNear(Bspt.Tuple center,
double distance)```
• #### enumSphere

```protected org.openscience.cdk.graph.rebond.Bspt.EnumerateSphere enumSphere(Bspt.Tuple center,
double distance)```
• #### enumHemiSphere

```protected org.openscience.cdk.graph.rebond.Bspt.EnumerateSphere enumHemiSphere(Bspt.Tuple center,
double distance)```

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