1 files changed, 104 insertions, 0 deletions
diff --git a/src/3rdparty/resonance-audio/resonance_audio/geometrical_acoustics/reflection_kernel.h b/src/3rdparty/resonance-audio/resonance_audio/geometrical_acoustics/reflection_kernel.h
new file mode 100644
index 000000000..10b34d5c7
--- /dev/null
+++ b/src/3rdparty/resonance-audio/resonance_audio/geometrical_acoustics/reflection_kernel.h
@@ -0,0 +1,104 @@
+/*
+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.
+*/
+
+#ifndef RESONANCE_AUDIO_GEOMETRICAL_ACOUSTICS_REFLECTION_KERNEL_H_
+#define RESONANCE_AUDIO_GEOMETRICAL_ACOUSTICS_REFLECTION_KERNEL_H_
+
+#include <array>
+#include <functional>
+#include <utility>
+
+#include "Eigen/Core"
+#include "base/constants_and_types.h"
+#include "base/logging.h"
+#include "geometrical_acoustics/acoustic_ray.h"
+
+namespace vraudio {
+
+// A class modeling reflections of acoustic rays. It takes in an incident ray
+// and computes the corresponding reflected ray. NOTE: not to be confused with
+// vraudio:Reflection, which models the reflection properties of a room.
+//
+// This class handles specular and diffuse reflections, randomly chosen based
+// on the scattering coefficient. Besides, a certain portion of the energy is
+// absorbed based on the absorption coefficient.
+//
+
+class ReflectionKernel {
+ public:
+  // Constructor.
+  //
+  // @param absorption_coefficients Fraction of energy being absorbed for each
+  //     frequency band. All values must be in [0.0, 1.0].
+  // @param scattering_coefficient Fraction of energy being scattered
+  //     (diffusely reflected). Must be in [0.0, 1.0].
+  // @param random_number_generator Random number generator to randomly select
+  //     reflection types as well as ray directions if needed. It should
+  //     implement operator() that returns a random value in [0.0, 1.0).
+  ReflectionKernel(
+      const std::array<float, kNumReverbOctaveBands>& absorption_coefficients,
+      float scattering_coefficient,
+      std::function<float()> random_number_generator)
+      : scattering_coefficient_(scattering_coefficient),
+        random_number_generator_(std::move(random_number_generator)) {
+    for (size_t i = 0; i < kNumReverbOctaveBands; ++i) {
+      reflection_coefficients_[i] = 1.0f - absorption_coefficients[i];
+      CHECK(reflection_coefficients_[i] >= 0.0f &&
+            reflection_coefficients_[i] <= 1.0f);
+    }
+    CHECK(scattering_coefficient_ >= 0.0f && scattering_coefficient_ <= 1.0f);
+  }
+
+  // Reflects a ray.
+  //
+  // @param incident_ray Incident (incoming) ray.
+  // @return Exitant (outgoing) ray, whose origin is on the intersection point,
+  //     with direction and energy calculated based on the type of reflection
+  //     and the incident ray.
+  AcousticRay Reflect(const AcousticRay& incident_ray) const;
+
+  // Reflects an incident ray to create a diffuse-rain ray, whose |direction|
+  // is from the reflection point to the listener position, and whose |t_far|
+  // is the distance between the reflection point and the listener position.
+  // All the other data are the copied from the provided
+  // |reference_reflected_ray|.
+  //
+  // @param incident_ray Incident ray.
+  // @param reflected_ray Reference reflected ray, from which the output
+  //     diffuse-rain ray copies all the data except for |direction| and
+  //     |t_far|.
+  // @param listener_position Listener position.
+  // @param direction_pdf Output probability density function that a reflected
+  //     ray is in the direction of the diffuse-rain ray. Will be used to
+  //     modulate the energy contribution from the diffuse-rain ray.
+  // @param diffuse_rain_ray Output diffuse-rain ray.
+  void ReflectDiffuseRain(const AcousticRay& incident_ray,
+                          const AcousticRay& reference_reflected_ray,
+                          const Eigen::Vector3f& listener_position,
+                          float* direction_pdf,
+                          AcousticRay* diffuse_rain_ray) const;
+
+ private:
+  std::array<float, kNumReverbOctaveBands> reflection_coefficients_;
+  const float scattering_coefficient_;
+
+  // Randon number generator for sampling reflection types and ray directions.
+  std::function<float()> random_number_generator_;
+};
+
+}  // namespace vraudio
+
+#endif  // RESONANCE_AUDIO_GEOMETRICAL_ACOUSTICS_REFLECTION_KERNEL_H_