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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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|
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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 1.2 2015/11/02 17:29:14 taschreg Exp taschreg $ |
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*/ |
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|
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#ifndef OOC_MORTON_H |
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#define OOC_MORTON_H |
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|
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#include "fvect.h" |
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#include <stdint.h> |
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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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#endif |
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