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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/path_tracer.h"
#include <cmath>
#include "base/logging.h"
#include "geometrical_acoustics/parallel_for.h"
#include "geometrical_acoustics/reflection_kernel.h"
namespace vraudio {
std::vector<Path> PathTracer::TracePaths(const AcousticSource& source,
size_t min_num_rays, size_t max_depth,
float energy_threshold) {
// The tracing would not work if the scene is not committed.
CHECK(scene_manager_.is_scene_committed());
// Find the actual number of rays to trace as the next square number greater
// or equal to |min_num_rays|.
const size_t sqrt_num_rays = static_cast<size_t>(
std::ceil(std::sqrt(static_cast<float>(min_num_rays))));
const size_t num_rays = sqrt_num_rays * sqrt_num_rays;
// In the current implementation, one ray does not spawn more than one child
// ray, hence the number of paths is the same as the number of rays from the
// source.
std::vector<Path> paths(num_rays);
std::vector<AcousticRay> rays_from_source =
source.GenerateStratifiedRays(num_rays, sqrt_num_rays);
const unsigned int num_threads = GetNumberOfHardwareThreads();
ParallelFor(
num_threads, num_rays,
[&rays_from_source, &paths, this, max_depth,
energy_threshold](size_t ray_index) {
if (max_depth == 0) return;
Path& path = paths.at(ray_index);
// Pre-allocate memory space for better performance.
path.rays.reserve(max_depth);
path.rays.push_back(rays_from_source[ray_index]);
size_t depth = 0;
while (true) {
AcousticRay& current_ray = path.rays.back();
// Stop generating new rays if the current ray escapes.
if (!current_ray.Intersect(scene_manager_.scene())) {
break;
}
// Stop generating new rays if |depth| reaches |max_depth|.
++depth;
if (depth >= max_depth) {
break;
}
// Handle interactions with scene geometries.
const ReflectionKernel& reflection =
scene_manager_.GetAssociatedReflectionKernel(
current_ray.intersected_primitive_id());
AcousticRay new_ray = reflection.Reflect(current_ray);
// Stop tracing if all energies in all frequency bands of the new ray
// are too low in energy.
bool is_energy_high_enough = false;
for (const float energy : new_ray.energies()) {
if (energy >= energy_threshold) {
is_energy_high_enough = true;
break;
}
}
if (!is_energy_high_enough) {
break;
}
path.rays.push_back(new_ray);
}
});
return paths;
}
} // namespace vraudio
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