1/* 2 * Copyright (C) 2010 Google Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of Apple Inc. ("Apple") nor the names of 14 * its contributors may be used to endorse or promote products derived 15 * from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29#include "config.h" 30 31#if ENABLE(WEB_AUDIO) 32 33#include "Distance.h" 34 35#include <algorithm> 36#include <math.h> 37 38namespace WebCore { 39 40DistanceEffect::DistanceEffect() 41 : m_model(ModelInverse) 42 , m_isClamped(true) 43 , m_refDistance(1.0) 44 , m_maxDistance(10000.0) 45 , m_rolloffFactor(1.0) 46{ 47} 48 49double DistanceEffect::gain(double distance) 50{ 51 // don't go beyond maximum distance 52 distance = std::min(distance, m_maxDistance); 53 54 // if clamped, don't get closer than reference distance 55 if (m_isClamped) 56 distance = std::max(distance, m_refDistance); 57 58 switch (m_model) { 59 case ModelLinear: 60 return linearGain(distance); 61 case ModelInverse: 62 return inverseGain(distance); 63 case ModelExponential: 64 return exponentialGain(distance); 65 } 66 ASSERT_NOT_REACHED(); 67 return 0.0; 68} 69 70double DistanceEffect::linearGain(double distance) 71{ 72 // We want a gain that decreases linearly from m_refDistance to 73 // m_maxDistance. The gain is 1 at m_refDistance. 74 return (1.0 - m_rolloffFactor * (distance - m_refDistance) / (m_maxDistance - m_refDistance)); 75} 76 77double DistanceEffect::inverseGain(double distance) 78{ 79 return m_refDistance / (m_refDistance + m_rolloffFactor * (distance - m_refDistance)); 80} 81 82double DistanceEffect::exponentialGain(double distance) 83{ 84 return pow(distance / m_refDistance, -m_rolloffFactor); 85} 86 87} // namespace WebCore 88 89#endif // ENABLE(WEB_AUDIO) 90