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