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9cfc70e7fe
Previously, the cos/sin table had to be a power of 2, but there are many use cases where the number of points is not necessarily a power of 2 so this change the constructor so it now takes in the number of points rather than the number of points as the exponent of a power of 2. The restriction is that the size must be divisible by 4.
74 lines
2.2 KiB
C++
74 lines
2.2 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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*/
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// Based on eos' sine tables
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#include "common/scummsys.h"
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#include "common/sinetables.h"
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namespace Common {
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SineTable::SineTable(int nPoints) {
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assert((nPoints >= 16) && (nPoints <= 65536)); // log2 space is in [4,16]
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assert(nPoints % 4 == 0);
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_nPoints = nPoints;
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_radResolution = 2.0 * M_PI / _nPoints;
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_refSize = _nPoints / 4;
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_table = new float[_nPoints / 2];
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// Table contains sin(2*pi*i/_nPoints) for 0<=i<_nPoints/4,
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// followed by _nPoints/2<=i<3_nPoints/4
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for (int i = 0; i < _nPoints / 4; i++)
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_table[i] = sin(i * _radResolution);
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for (int i = 0; i < _nPoints / 4; i++)
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_table[_nPoints / 4 + i] = -_table[i];
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}
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float SineTable::at(int index) const {
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assert((index >= 0) && (index < _nPoints));
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if (index < _refSize)
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// [0,pi/2)
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return _table[index];
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if (index == _refSize)
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// pi/2
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return 1.0f; // sin(pi/2) = 1.0
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if ((index > _refSize) && (index < 2 * _refSize))
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// (pi/2,pi)
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return _table[2 * _refSize - index];
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if ((index >= 2 * _refSize) && (index < 3 * _refSize))
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// [pi,3/2pi)
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return -_table[index - 2 * _refSize];
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if ((index > 3 * _refSize) && (index < _nPoints))
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// (3/2pi,2pi)
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return -_table[_nPoints - index];
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return -1.0f; // sin(3pi/2) = -1.0
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}
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SineTable::~SineTable() {
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delete[] _table;
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}
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} // End of namespace Common
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