| /* |
| * Copyright (C) 2010 Google Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of |
| * its contributors may be used to endorse or promote products derived |
| * from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY |
| * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
| * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY |
| * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #include "config.h" |
| |
| #if ENABLE(WEB_AUDIO) |
| |
| #include "platform/audio/Distance.h" |
| #include "wtf/Assertions.h" |
| |
| #include <math.h> |
| #include <algorithm> |
| |
| using namespace std; |
| |
| namespace WebCore { |
| |
| DistanceEffect::DistanceEffect() |
| : m_model(ModelInverse) |
| , m_isClamped(true) |
| , m_refDistance(1.0) |
| , m_maxDistance(10000.0) |
| , m_rolloffFactor(1.0) |
| { |
| } |
| |
| double DistanceEffect::gain(double distance) |
| { |
| // don't go beyond maximum distance |
| distance = min(distance, m_maxDistance); |
| |
| // if clamped, don't get closer than reference distance |
| if (m_isClamped) |
| distance = max(distance, m_refDistance); |
| |
| switch (m_model) { |
| case ModelLinear: |
| return linearGain(distance); |
| case ModelInverse: |
| return inverseGain(distance); |
| case ModelExponential: |
| return exponentialGain(distance); |
| } |
| ASSERT_NOT_REACHED(); |
| return 0.0; |
| } |
| |
| double DistanceEffect::linearGain(double distance) |
| { |
| // We want a gain that decreases linearly from m_refDistance to |
| // m_maxDistance. The gain is 1 at m_refDistance. |
| return (1.0 - m_rolloffFactor * (distance - m_refDistance) / (m_maxDistance - m_refDistance)); |
| } |
| |
| double DistanceEffect::inverseGain(double distance) |
| { |
| return m_refDistance / (m_refDistance + m_rolloffFactor * (distance - m_refDistance)); |
| } |
| |
| double DistanceEffect::exponentialGain(double distance) |
| { |
| return pow(distance / m_refDistance, -m_rolloffFactor); |
| } |
| |
| } // namespace WebCore |
| |
| #endif // ENABLE(WEB_AUDIO) |