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 Computer, 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 38 using namespace std; 39 40 namespace WebCore { 41 42 DistanceEffect::DistanceEffect() 43 : m_model(ModelInverse) 44 , m_isClamped(true) 45 , m_refDistance(1.0) 46 , m_maxDistance(10000.0) 47 , m_rolloffFactor(1.0) 48 { 49 } 50 51 double DistanceEffect::gain(double distance) 52 { 53 // don't go beyond maximum distance 54 distance = min(distance, m_maxDistance); 55 56 // if clamped, don't get closer than reference distance 57 if (m_isClamped) 58 distance = max(distance, m_refDistance); 59 60 switch (m_model) { 61 case ModelLinear: 62 return linearGain(distance); 63 break; 64 case ModelInverse: 65 return inverseGain(distance); 66 break; 67 case ModelExponential: 68 return exponentialGain(distance); 69 break; 70 71 default: 72 return 0.0; 73 } 74 } 75 76 double DistanceEffect::linearGain(double distance) 77 { 78 return (1.0 - m_rolloffFactor * (distance - m_refDistance)) / (m_maxDistance - m_refDistance); 79 } 80 81 double DistanceEffect::inverseGain(double distance) 82 { 83 return m_refDistance / (m_refDistance + m_rolloffFactor * (distance - m_refDistance)); 84 } 85 86 double DistanceEffect::exponentialGain(double distance) 87 { 88 return pow(distance / m_refDistance, -m_rolloffFactor); 89 } 90 91 } // namespace WebCore 92 93 #endif // ENABLE(WEB_AUDIO) 94