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(DistanceModelType::Inverse)
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 DistanceModelType::Linear:
60 return linearGain(distance);
61 case DistanceModelType::Inverse:
62 return inverseGain(distance);
63 case DistanceModelType::Exponential:
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