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RadiancePmap/morton.h
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morton.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, "Daylight Redirecting Components",
SNSF #179067, "Light Fields for Spatio-Temporal Glare Assessment")
======================================================================
$Id$
*/
#ifndef _MORTON_H
#define _MORTON_H
#include "fvect.h"
#include <stdint.h>
/* Type to represent Morton codes (Z-curve indices) */
typedef uint64_t MortonIdx;
/* Number of bits per dimension for Morton code (Z-curve index) in 2D
and 3D. 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. */
#define MORTON3D_BITS 21
#define MORTON3D_MAX (((MortonIdx)1 << MORTON3D_BITS) - 1)
#define MORTON2D_BITS 32
#define MORTON2D_MAX (((MortonIdx)1 << MORTON2D_BITS) - 1)
/* Interleave lower MORTONxx_BITS bits of k with 00 for 3D (resp. 0 for
2D), resulting in 3*MORTON3D_BITS (resp. 2*MORTON2D_BITS) bits. This
is an optimised "bitmask hack" version code taken from:
http://www.forceflow.be/2013/10/07/
morton-encodingdecoding-through-bit-interleaving-implementations/
and (for 32-bit codes):
https://fgiesen.wordpress.com/2009/12/13/decoding-morton-codes/
*/
#define Morton3DBitInterleave(k) ((k) &= MORTON3D_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 \
)
#define Morton2DBitInterleave(k) ((k) &= MORTON2D_MAX, \
(k) = ((k) | (k) << 16) & 0x0000ffff0000ffff, \
(k) = ((k) | (k) << 8) & 0x00ff00ff00ff00ff, \
(k) = ((k) | (k) << 4) & 0x0f0f0f0f0f0f0f0f, \
(k) = ((k) | (k) << 2) & 0x3333333333333333, \
(k) = ((k) | (k) << 1) & 0x5555555555555555 \
)
/* Compute Morton code (Z-curve index) of length 3 * MORTON3D_BITS bits
for 3D key within bounding box defined by org and scaled to maximum
index with scale */
MortonIdx Key2Morton3D (const FVECT key, const FVECT org, RREAL scale);
/* As above, but compute Morton code of length 2 * MORTON2D_BITS bits
for 2D key */
MortonIdx Key2Morton2D (const RREAL key [2], const RREAL org [2],
RREAL scale
);
#endif /* _MORTON_H */
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