HTMfunc

java.lang.Object
- htm.core.HTMfunc

```
public class HTMfunc
extends Object
```
These are the core routines for the HTM. They are a direct lift from cc_aux but modifed along the lined of the new design In pratically all cases below a double[] is a vector of 3 numbers representing x,y,z in the unit sphere.
```
  Current Version
  ===============
  ID:   $Id: HTMfunc.java,v 1.5 2003/02/19 15:46:11 womullan Exp $
  Revision:     $Revision: 1.5 $
  Date/time:    $Date: 2003/02/19 15:46:11 $
 
```

Field Summary

Fields
Modifier and Type	Field and Description
`(package private) static Object[]`	`anchor`
`(package private) static Base[]`	`bases`
`static double`	`Epsilon`
`(package private) static double`	`gEpsilon`
`static double`	`HTM_INVALID_ID`
`static int`	`HTMNAMEMAX`
`static long`	`IDHIGHBIT`
`static long`	`IDHIGHBIT2`
`static int`	`IDSIZE`
`static int`	`iN0`
`static int`	`iN1`
`static int`	`iN2`
`static int`	`iN3`
`static int`	`iS0`
`static int`	`iS1`
`static int`	`iS2`
`static int`	`iS3`
`(package private) static Object[]`	`N_indexes`
`static double`	`Pi`
`static double`	`Pr`
`(package private) static Object[]`	`S_indexes`
`static double`	`sqrt3`
`static Boolean`	`verbose`

Constructor Summary

Constructors
Constructor and Description

HTMfunc()

Constructors
Constructor and Description
`HTMfunc()`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`protected static void`	`copy_vec(double[] d, double[] s)` simple utility funtion which copies one vector over another.
`static double`	`distance(double[] v1, double[] v2)` return the angular distance between two vectors ACOS (V1 .
`static double`	`distance(long htmId1, long htmId2)` return the angular distance between two htmids gets the vectors of the mid points and uses thoose to compute distance
`static double`	`distance(String htm1, String htm2)` return the angular distance between two htm names gets the viectors of the mid points and uses thoose to compute distance
`static int`	`idLevel(long htmid)` idLevel is a trusting method (assumes that the id is well formed and valid) that returns the level of the trixel represented by the given 64 bit htmId.
`static String`	`idToName(long id)` Walk the bits of the id and convert it to a string like N012.
`static double[]`	`idToPoint(long htmId)` gets the name from the id and calls idToPoint with it.
`static double[]`	`idToPoint(String name)` for a given ID get back the approximate center of the triangle.
`static boolean`	`isinside(double[] p, double[] v1, double[] v2, double[] v3)` for a given vector p is it contained in the triangle whose corners are given by the vectors v1, v2,v3.
`static String`	`lookup(double x, double y, double z, int depth)`
`static String`	`lookup(double ra, double dec, int depth)` For given ra and dec lookup the HTMID to given depth HTM works in vectors so this basically converts ra dec to a vector and calls lookup for the vector.
`static long`	`lookupId(double x, double y, double z, int depth)` looks up the name of a vector x,y,z and converts the name to an id
`static long`	`lookupId(double ra, double dec, int depth)`
`protected static void`	`m4_midpoint(double[] v1, double[] v2, double[] w)`
`static long`	`nameToId(String name)` for a given name i.e.
`static Object[]`	`nameToTriangle(String name)` Like name2Id but instaed of returning the htmId return v0,v1,v2 vetors representin the corners of the trinagle
`static double[]`	`radecToVector(double ra, double dec)` convert ra dec to a vector
`protected static int`	`startpane(double[] v1, double[] v2, double[] v3, double xin, double yin, double zin, StringBuffer name)` where to start in the HTM quadtree when looking for a vectors home xin yin zin are thin input vector v1 v2 v3 and name are loaded with the initial tringle points and the name of the triangle

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - verbose
```
public static final Boolean verbose
```
  - Pi
```
public static double Pi
```
  - Pr
```
public static double Pr
```
  - Epsilon
```
public static double Epsilon
```
  - sqrt3
```
public static double sqrt3
```
  - IDSIZE
```
public static final int IDSIZE
```
    See Also:
    
    Constant Field Values
  - IDHIGHBIT
```
public static final long IDHIGHBIT
```
    See Also:
    
    Constant Field Values
  - IDHIGHBIT2
```
public static final long IDHIGHBIT2
```
    See Also:
    
    Constant Field Values
  - HTMNAMEMAX
```
public static final int HTMNAMEMAX
```
    See Also:
    
    Constant Field Values
  - gEpsilon
```
static double gEpsilon
```
  - HTM_INVALID_ID
```
public static final double HTM_INVALID_ID
```
    See Also:
    
    Constant Field Values
  - iS2
```
public static final int iS2
```
    See Also:
    
    Constant Field Values
  - iN1
```
public static final int iN1
```
    See Also:
    
    Constant Field Values
  - iS1
```
public static final int iS1
```
    See Also:
    
    Constant Field Values
  - iN2
```
public static final int iN2
```
    See Also:
    
    Constant Field Values
  - iS3
```
public static final int iS3
```
    See Also:
    
    Constant Field Values
  - iN0
```
public static final int iN0
```
    See Also:
    
    Constant Field Values
  - iS0
```
public static final int iS0
```
    See Also:
    
    Constant Field Values
  - iN3
```
public static final int iN3
```
    See Also:
    
    Constant Field Values
  - anchor
```
static Object[] anchor
```
  - S_indexes
```
static Object[] S_indexes
```
  - N_indexes
```
static Object[] N_indexes
```
  - bases
```
static Base[] bases
```
- Constructor Detail
  - HTMfunc
```
public HTMfunc()
```
- Method Detail
  - startpane
```
protected static int startpane(double[] v1,
                               double[] v2,
                               double[] v3,
                               double xin,
                               double yin,
                               double zin,
                               StringBuffer name)
                        throws HTMException
```
    where to start in the HTM quadtree when looking for a vectors home xin yin zin are thin input vector v1 v2 v3 and name are loaded with the initial tringle points and the name of the triangle
    
    Throws:
    
    HTMException
  - m4_midpoint
```
protected static final void m4_midpoint(double[] v1,
                                        double[] v2,
                                        double[] w)
```
  - lookup
```
public static String lookup(double x,
                            double y,
                            double z,
                            int depth)
                     throws HTMException
```
    Throws:
    
    HTMException
  - lookupId
```
public static long lookupId(double x,
                            double y,
                            double z,
                            int depth)
                     throws HTMException
```
    looks up the name of a vector x,y,z and converts the name to an id
    
    Throws:
    
    HTMException
  - lookup
```
public static String lookup(double ra,
                            double dec,
                            int depth)
                     throws HTMException
```
    For given ra and dec lookup the HTMID to given depth HTM works in vectors so this basically converts ra dec to a vector and calls lookup for the vector.
    
    Throws:
    
    HTMException
  - radecToVector
```
public static double[] radecToVector(double ra,
                                     double dec)
```
    convert ra dec to a vector
  - lookupId
```
public static long lookupId(double ra,
                            double dec,
                            int depth)
                     throws HTMException
```
    Throws:
    
    HTMException
  - isinside
```
public static boolean isinside(double[] p,
                               double[] v1,
                               double[] v2,
                               double[] v3)
```
    for a given vector p is it contained in the triangle whose corners are given by the vectors v1, v2,v3.
  - nameToId
```
public static long nameToId(String name)
                     throws HTMException
```
    for a given name i.e. N301022 convert it to its 64bit htmId effectively this walks trough the string in reverse order and sets the bits of a long number according to the charector in the String. The name has always the same structure, it begins with an N or S, indicating north or south cap and then numbers 0-3 follow indicating which child to descend into. So for a depth-5-index we have strings like N012023 S000222 N102302 etc Each of the numbers correspond to 2 bits of code (00 01 10 11) in the uint64. The first two bits are 10 for S and 11 for N. For example N 0 1 2 0 2 3 11000110001011 = 12683 (dec) The leading bits are always 0
    
    Throws:
    
    HTMException
  - idLevel
```
public static int idLevel(long htmid)
```
    idLevel is a trusting method (assumes that the id is well formed and valid) that returns the level of the trixel represented by the given 64 bit htmId. This determines the index of the first bit set by continually left shifting the htmid 2 bits at a time until a set bit is found in the highest position. 2 bits are used as each number in an HTM Name like N012 is represented by two bits. Also the number of bits used dived by two is the level of the htmId +2 we have +2 because of the N0,S1 etc prefixes. So an id with bit 64 set is level 30 (64/2 -2)
  - idToName
```
public static String idToName(long id)
                       throws HTMException
```
    Walk the bits of the id and convert it to a string like N012. sucessivley look at each pair of bits and convert it to 0,1,2 or 3. Finally use the highest bit to set N or S in the string. The first bit pair gives N (11) or S (10). The subsequent bit-pairs give the numbers 0-3: (00, 01, 10, 11). Example: In the first level there are 8 nodes, and we get the names from numbers 8 through 15 giving S0,S1,S2,S3,N0,N1,N2,N3. The order is always ascending starting from S0000.. to N3333...
    
    Throws:
    
    HTMException
  - nameToTriangle
```
public static Object[] nameToTriangle(String name)
```
    Like name2Id but instaed of returning the htmId return v0,v1,v2 vetors representin the corners of the trinagle
    
    Returns:
    
    Object[] which is holding 3 double[] for v0 v1 v2
  - copy_vec
```
protected static void copy_vec(double[] d,
                               double[] s)
```
    simple utility funtion which copies one vector over another. this uses System.arraycopy which should be efficient. It assumes both arrays are the same lenght however it will copy all odf s to d so theoretically d could be longer than s.
    
    Parameters:
    
    d - destination of copy
    
    s - source of copy
  - idToPoint
```
public static double[] idToPoint(String name)
                          throws HTMException
```
    for a given ID get back the approximate center of the triangle. This may be used as an inverse of lookup however bear in mind many points may fall in a triangle while only the center point will be returned from this function. The name is used to get the triange corners and these are then averaged to get a center point. The resultant vector is not normalized.
    
    Throws:
    
    HTMException
  - idToPoint
```
public static double[] idToPoint(long htmId)
                          throws HTMException
```
    gets the name from the id and calls idToPoint with it.
    
    Throws:
    
    HTMException
  - distance
```
public static double distance(double[] v1,
                              double[] v2)
```
    return the angular distance between two vectors ACOS (V1 . V2)
  - distance
```
public static double distance(long htmId1,
                              long htmId2)
                       throws HTMException
```
    return the angular distance between two htmids gets the vectors of the mid points and uses thoose to compute distance
    
    Throws:
    
    HTMException
  - distance
```
public static double distance(String htm1,
                              String htm2)
                       throws HTMException
```
    return the angular distance between two htm names gets the viectors of the mid points and uses thoose to compute distance
    
    Throws:
    
    HTMException

Class HTMfunc

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

verbose

Pi

Pr

Epsilon

sqrt3

IDSIZE

IDHIGHBIT

IDHIGHBIT2

HTMNAMEMAX

gEpsilon

HTM_INVALID_ID

iS2

iN1

iS1

iN2

iS3

iN0

iS0

iN3

anchor

S_indexes

N_indexes

bases

Constructor Detail

HTMfunc

Method Detail

startpane

m4_midpoint

lookup

lookupId

lookup

radecToVector

lookupId

isinside

nameToId

idLevel

idToName

nameToTriangle

copy_vec

idToPoint

idToPoint

distance

distance

distance