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RadiancePmap/oocmorton.h
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oocmorton.h
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/*
======================================================================
Routines to generate and compare Morton Codes, i.e. indices on space
filling Z-curves.
Roland Schregle (roland.schregle@{hslu.ch, gmail.com})
(c) Lucerne University of Applied Sciences and Arts,
supported by the Swiss National Science Foundation (SNSF, #147053)
======================================================================
$Id: oocmorton.h,v 2.1 2016/05/17 17:39:47 rschregle Exp $
*/
#ifndef OOC_MORTON_H
#define OOC_MORTON_H
#include "fvect.h"
#include <stdint.h>
/* Type to represent Morton codes (Z-curve indices) as sort keys */
typedef uint64_t OOC_MortonIdx;
/* Number of bits per dimension for Morton code (Z-curve index) used to
* sort records. This corresponds to the maximum number of bounding box
* subdivisions which can be resolved per axis; further subdivisions will
* map to the same Morton code, thus invalidating the sort! */
#define OOC_MORTON_BITS 21
#define OOC_MORTON_MAX (((OOC_MortonIdx)1 << OOC_MORTON_BITS) - 1)
/* Interleave lower OOC_MORTON_BITS bits of k with 00, resulting in
* 3*OOC_MORTON_BITS bits. Optimised "bitmask hack" version. This code
* taken from:
* http://www.forceflow.be/2013/10/07/
* morton-encodingdecoding-through-bit-interleaving-implementations/ */
#define OOC_BitInterleave(k) \
((k) &= OOC_MORTON_MAX, \
(k) = ((k) | (k) << 32) & 0x001f00000000ffff, \
(k) = ((k) | (k) << 16) & 0x001f0000ff0000ff, \
(k) = ((k) | (k) << 8) & 0x100f00f00f00f00f, \
(k) = ((k) | (k) << 4) & 0x10c30c30c30c30c3, \
(k) = ((k) | (k) << 2) & 0x1249249249249249)
/* Compute Morton code (Z-curve index) of length 3 * OOC_MORTON_BITS bits
* for 3D key within bounding box defined by org and scaled to maximum
* index with scale */
OOC_MortonIdx OOC_Key2Morton (const FVECT key, const FVECT org,
RREAL scale);
#endif
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