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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 "geometrical_acoustics/impulse_response_computer.h"
#include <utility>
#include "Eigen/Core"
#include "base/logging.h"
#include "geometrical_acoustics/parallel_for.h"
#include "geometrical_acoustics/reflection_kernel.h"
namespace vraudio {
using Eigen::Vector3f;
ImpulseResponseComputer::ImpulseResponseComputer(
float listener_sphere_radius, float sampling_rate,
std::unique_ptr<std::vector<AcousticListener>> listeners,
SceneManager* scene_manager)
: listeners_(std::move(listeners)),
collection_kernel_(listener_sphere_radius, sampling_rate),
scene_manager_(scene_manager),
finalized_(false),
num_total_paths_(0) {
CHECK_NOTNULL(listeners_.get());
scene_manager->BuildListenerScene(*listeners_, listener_sphere_radius);
}
ImpulseResponseComputer::~ImpulseResponseComputer() {}
void ImpulseResponseComputer::CollectContributions(
const std::vector<Path>& paths_batch) {
// Do not collect anymore if finalized.
if (finalized_) {
return;
}
CHECK(scene_manager_->is_scene_committed());
CHECK(scene_manager_->is_listener_scene_committed());
const unsigned int num_threads = GetNumberOfHardwareThreads();
ParallelFor(
num_threads, paths_batch.size(), [&paths_batch, this](size_t path_index) {
const Path& path = paths_batch.at(path_index);
const AcousticRay* previous_ray = nullptr;
AcousticRay diffuse_rain_ray;
for (const AcousticRay& ray : path.rays) {
// Handle diffuse reflections separately using the diffuse rain
// algorithm. For details, see "A Fast Reverberation Estimator for
// Virtual Environments" by Schroder et al., 2007.
if (ray.type() == AcousticRay::RayType::kDiffuse &&
previous_ray != nullptr) {
// Connect each listener from the reflection point.
for (AcousticListener& listener : *listeners_) {
const ReflectionKernel& reflection =
scene_manager_->GetAssociatedReflectionKernel(
previous_ray->intersected_primitive_id());
float reflection_pdf = 0.0f;
reflection.ReflectDiffuseRain(*previous_ray, ray,
listener.position, &reflection_pdf,
&diffuse_rain_ray);
if (!diffuse_rain_ray.Intersect(scene_manager_->scene())) {
// Get PDF from the reflection kernel that the previous ray
// intersects.
collection_kernel_.CollectDiffuseRain(
diffuse_rain_ray, 1.0f /* weight */, reflection_pdf,
&listener);
}
}
previous_ray = &ray;
continue;
}
// |ray| may intersect multiple listener spheres. We handle the
// intersections one-by-one as following:
// 1. Find the first intersected sphere S. The ray's data will be
// modified so that ray.t_far() corresponds to the intersection
// point. Terminate if no intersection is found.
// 2. Collect contribution to the listener associated to S.
// 3. Spawn a sub-ray that starts at the intersection point (moved
// slightly inside S) and repeat 1.
//
// Since the origin of the new sub-ray is inside sphere S, it does not
// intersect with S again (according to our definition of
// intersections; see Sphere::SphereIntersection()).
//
// Each of the sub-rays has the same origin and direction as the
// original ray, but with t_near and t_far partitioning the interval
// between the original ray's t_near and t_far. For example:
//
// ray: t_near = 0.0 ------------------------------> t_far = 5.0
// sub_ray_1: t_near = 0.0 -------> t_far = 2.0
// sub_ray_2: t_near = 2.0 ---------> t_far = 5.0
AcousticRay sub_ray(ray.origin(), ray.direction(), ray.t_near(),
ray.t_far(), ray.energies(), ray.type(),
ray.prior_distance());
// Norm of |ray.direction|. Useful in computing
// |sub_ray.prior_distance| later.
const float ray_direction_norm = Vector3f(ray.direction()).norm();
// In theory with sufficient AcousticRay::kRayEpsilon, the same sphere
// should not be intersected twice by the same ray segment. In
// practice, due to floating-point inaccuracy, this might still
// happen. We explicitly prevent double-counting by checking whether
// the intersected sphere id has changed.
unsigned int previous_intersected_sphere_id = RTC_INVALID_GEOMETRY_ID;
// To prevent an infinite loop, terminate if one ray segment has more
// intersections than the number of listeners, which is an upper bound
// of the number of actually contributing sub-rays.
size_t num_intersections = 0;
while (sub_ray.Intersect(scene_manager_->listener_scene()) &&
num_intersections < listeners_->size()) {
const unsigned int sphere_id = sub_ray.intersected_geometry_id();
if (sphere_id != previous_intersected_sphere_id) {
AcousticListener& listener = listeners_->at(
scene_manager_->GetListenerIndexFromSphereId(sphere_id));
collection_kernel_.Collect(sub_ray, 1.0f /* weight */, &listener);
} else {
LOG(WARNING) << "Double intersection with sphere[" << sphere_id
<< "]; contribution skipped. Consider increasing "
<< "AcousticRay::kRayEpsilon";
}
previous_intersected_sphere_id = sphere_id;
// Spawn a new sub-ray whose t_near corresponds to the intersection
// point. The new sub-ray's |prior_distance| field is extended by
// the distance traveled by the old sub-ray up to the intersection
// point.
const float new_prior_distance =
sub_ray.prior_distance() +
(sub_ray.t_far() - sub_ray.t_near()) * ray_direction_norm;
sub_ray = AcousticRay(ray.origin(), ray.direction(),
sub_ray.t_far() + AcousticRay::kRayEpsilon,
ray.t_far(), ray.energies(), ray.type(),
new_prior_distance);
++num_intersections;
}
previous_ray = &ray;
}
});
num_total_paths_ += paths_batch.size();
}
const std::vector<AcousticListener>&
ImpulseResponseComputer::GetFinalizedListeners() {
DCHECK_GT(num_total_paths_, 0U);
if (!finalized_) {
// For a Monte Carlo method that estimates a value with N samples,
// <estimated value> = 1/N * sum(<value of a sample>). We apply the
// 1/N weight after all impulse responses for all listeners are collected.
const float monte_carlo_weight =
1.0f / static_cast<float>(num_total_paths_);
for (AcousticListener& listener : *listeners_) {
for (std::vector<float>& responses_in_band :
listener.energy_impulse_responses) {
for (float& response : responses_in_band) {
response *= monte_carlo_weight;
}
}
}
finalized_ = true;
}
return *listeners_;
}
} // namespace vraudio
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