1 files changed, 101 insertions, 0 deletions
diff --git a/src/3rdparty/resonance-audio/resonance_audio/graph/occlusion_node.cc b/src/3rdparty/resonance-audio/resonance_audio/graph/occlusion_node.cc
new file mode 100644
index 000000000..3805836f5
--- /dev/null
+++ b/src/3rdparty/resonance-audio/resonance_audio/graph/occlusion_node.cc
@@ -0,0 +1,101 @@
+/*
+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 "graph/occlusion_node.h"
+
+#include <cmath>
+
+#include "base/logging.h"
+#include "base/spherical_angle.h"
+
+#include "dsp/occlusion_calculator.h"
+
+namespace vraudio {
+
+namespace {
+
+// Low pass filter coefficient for smoothing the applied occlusion. This avoids
+// sudden unrealistic changes in the volume of a sound object. Range [0, 1].
+// The value below has been calculated empirically.
+const float kOcclusionSmoothingCoefficient = 0.75f;
+
+// This function provides first order low-pass filtering. It is used to smooth
+// the occlusion parameter.
+float Interpolate(float coefficient, float previous_value, float target_value) {
+  return target_value + coefficient * (previous_value - target_value);
+}
+
+}  // namespace
+
+OcclusionNode::OcclusionNode(SourceId source_id,
+                             const SystemSettings& system_settings)
+    : system_settings_(system_settings),
+      low_pass_filter_(0.0f),
+      current_occlusion_(0.0f),
+      output_buffer_(kNumMonoChannels, system_settings.GetFramesPerBuffer()) {
+  output_buffer_.Clear();
+  output_buffer_.set_source_id(source_id);
+}
+
+const AudioBuffer* OcclusionNode::AudioProcess(const NodeInput& input) {
+
+  const AudioBuffer* input_buffer = input.GetSingleInput();
+  DCHECK(input_buffer);
+  DCHECK_EQ(input_buffer->source_id(), output_buffer_.source_id());
+
+  const auto source_parameters =
+      system_settings_.GetSourceParameters(input_buffer->source_id());
+  if (source_parameters == nullptr) {
+    LOG(WARNING) << "Could not find source parameters";
+    return nullptr;
+  }
+
+  const WorldPosition& listener_position = system_settings_.GetHeadPosition();
+  const WorldRotation& listener_rotation = system_settings_.GetHeadRotation();
+  const ObjectTransform& source_transform = source_parameters->object_transform;
+  // Compute the relative listener/source direction in spherical angles.
+  WorldPosition relative_direction;
+  GetRelativeDirection(listener_position, listener_rotation,
+                       source_transform.position, &relative_direction);
+  const SphericalAngle listener_direction =
+      SphericalAngle::FromWorldPosition(relative_direction);
+
+  GetRelativeDirection(source_transform.position, source_transform.rotation,
+                       listener_position, &relative_direction);
+  const SphericalAngle source_direction =
+      SphericalAngle::FromWorldPosition(relative_direction);
+  // Calculate low-pass filter coefficient based on listener/source directivity
+  // and occlusion values.
+  const float listener_directivity = CalculateDirectivity(
+      source_parameters->listener_directivity_alpha,
+      source_parameters->listener_directivity_order, listener_direction);
+  const float source_directivity = CalculateDirectivity(
+      source_parameters->directivity_alpha,
+      source_parameters->directivity_order, source_direction);
+  current_occlusion_ =
+      Interpolate(kOcclusionSmoothingCoefficient, current_occlusion_,
+                  source_parameters->occlusion_intensity);
+  const float filter_coefficient = CalculateOcclusionFilterCoefficient(
+      listener_directivity * source_directivity, current_occlusion_);
+  low_pass_filter_.SetCoefficient(filter_coefficient);
+  if (!low_pass_filter_.Filter((*input_buffer)[0], &output_buffer_[0])) {
+    return input_buffer;
+  }
+  // Copy buffer parameters.
+  return &output_buffer_;
+}
+
+}  // namespace vraudio