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/*
Copyright 2018 Google Inc. All Rights Reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS-IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#include "dsp/distance_attenuation.h"
#include <algorithm>
#include <cmath>
#include "base/constants_and_types.h"
namespace vraudio {
float ComputeLogarithmicDistanceAttenuation(
const WorldPosition& listener_position,
const WorldPosition& source_position, float min_distance,
float max_distance) {
const float distance = (listener_position - source_position).norm();
if (distance > max_distance) {
return 0.0f;
}
// Logarithmic attenuation.
const float min_distance_allowed =
std::max(min_distance, kNearFieldThreshold);
if (distance > min_distance_allowed) {
const float attenuation_interval = max_distance - min_distance_allowed;
if (attenuation_interval > kEpsilonFloat) {
// Compute the distance attenuation value by the logarithmic curve
// "1 / (d + 1)" with an offset of |min_distance_allowed|.
const float relative_distance = distance - min_distance_allowed;
const float attenuation = 1.0f / (relative_distance + 1.0f);
// Shift the curve downwards by the attenuation value at |max_distance|,
// and scale the value by the inverse of it in order to keep the curve's
// peak value 1 at |min_distance_allowed|.
const float attenuation_max = 1.0f / (1.0f + attenuation_interval);
return (attenuation - attenuation_max) / (1.0f - attenuation_max);
}
}
return 1.0f;
}
float ComputeLinearDistanceAttenuation(const WorldPosition& listener_position,
const WorldPosition& source_position,
float min_distance, float max_distance) {
const float distance = (listener_position - source_position).norm();
if (distance > max_distance) {
return 0.0f;
}
// Linear attenuation.
const float min_distance_allowed =
std::max(min_distance, kNearFieldThreshold);
if (distance > min_distance_allowed) {
const float attenuation_interval = max_distance - min_distance_allowed;
if (attenuation_interval > kEpsilonFloat) {
return (max_distance - distance) / attenuation_interval;
}
}
return 1.0f;
}
float ComputeNearFieldEffectGain(const WorldPosition& listener_position,
const WorldPosition& source_position) {
const float distance = (listener_position - source_position).norm();
if (distance < kNearFieldThreshold) {
return (1.0f / std::max(distance, kMinNearFieldDistance)) - 1.0f;
}
return 0.0f;
}
void UpdateAttenuationParameters(float master_gain, float reflections_gain,
float reverb_gain,
const WorldPosition& listener_position,
SourceParameters* parameters) {
// Compute distance attenuation.
const WorldPosition& source_position = parameters->object_transform.position;
const auto rolloff_model = parameters->distance_rolloff_model;
const float min_distance = parameters->minimum_distance;
const float max_distance = parameters->maximum_distance;
float distance_attenuation = 0.0f;
switch (rolloff_model) {
case DistanceRolloffModel::kLogarithmic:
distance_attenuation = ComputeLogarithmicDistanceAttenuation(
listener_position, source_position, min_distance, max_distance);
break;
case DistanceRolloffModel::kLinear:
distance_attenuation = ComputeLinearDistanceAttenuation(
listener_position, source_position, min_distance, max_distance);
break;
case DistanceRolloffModel::kNone:
default:
// Distance attenuation is already set by the user.
distance_attenuation = parameters->distance_attenuation;
break;
}
// Update gain attenuations.
const float input_gain = master_gain * parameters->gain;
const float direct_attenuation = input_gain * distance_attenuation;
const float room_effects_attenuation = parameters->room_effects_gain;
parameters->attenuations[AttenuationType::kInput] = input_gain;
parameters->attenuations[AttenuationType::kDirect] = direct_attenuation;
parameters->attenuations[AttenuationType::kReflections] =
room_effects_attenuation * direct_attenuation * reflections_gain;
parameters->attenuations[AttenuationType::kReverb] =
room_effects_attenuation * input_gain * reverb_gain;
}
} // namespace vraudio
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