// VolPathIntegrator Method Definitions
void VolPathIntegrator::Preprocess(const Scene &scene, Sampler &sampler) {
lightDistribution =
CreateLightSampleDistribution(lightSampleStrategy, scene);
}
void BDPTIntegrator::Render(const Scene &scene) {
std::unique_ptr<LightDistribution> lightDistribution =
CreateLightSampleDistribution(lightSampleStrategy, scene);
// Compute a reverse mapping from light pointers to offsets into the
// scene lights vector (and, equivalently, offsets into
// lightDistr). Added after book text was finalized; this is critical
// to reasonable performance with 100s+ of light sources.
std::unordered_map<const Light *, size_t> lightToIndex;
for (size_t i = 0; i < scene.lights.size(); ++i)
lightToIndex[scene.lights[i].get()] = i;
// Partition the image into tiles
Film *film = camera->film;
const Bounds2i sampleBounds = film->GetSampleBounds();
const Vector2i sampleExtent = sampleBounds.Diagonal();
const int tileSize = 16;
const int nXTiles = (sampleExtent.x + tileSize - 1) / tileSize;
const int nYTiles = (sampleExtent.y + tileSize - 1) / tileSize;
ProgressReporter reporter(nXTiles * nYTiles, "Rendering");
// Allocate buffers for debug visualization
const int bufferCount = (1 + maxDepth) * (6 + maxDepth) / 2;
std::vector<std::unique_ptr<Film>> weightFilms(bufferCount);
if (visualizeStrategies || visualizeWeights) {
for (int depth = 0; depth <= maxDepth; ++depth) {
for (int s = 0; s <= depth + 2; ++s) {
int t = depth + 2 - s;
if (t == 0 || (s == 1 && t == 1)) continue;
std::string filename =
StringPrintf("bdpt_d%02i_s%02i_t%02i.exr", depth, s, t);
weightFilms[BufferIndex(s, t)] = std::unique_ptr<Film>(new Film(
film->fullResolution,
Bounds2f(Point2f(0, 0), Point2f(1, 1)),
std::unique_ptr<Filter>(CreateBoxFilter(ParamSet())),
film->diagonal * 1000, filename, 1.f));
}
}
}
// Render and write the output image to disk
if (scene.lights.size() > 0) {
ParallelFor2D([&](const Point2i tile) {
// Render a single tile using BDPT
MemoryArena arena;
int seed = tile.y * nXTiles + tile.x;
std::unique_ptr<Sampler> tileSampler = sampler->Clone(seed);
int x0 = sampleBounds.pMin.x + tile.x * tileSize;
int x1 = std::min(x0 + tileSize, sampleBounds.pMax.x);
int y0 = sampleBounds.pMin.y + tile.y * tileSize;
int y1 = std::min(y0 + tileSize, sampleBounds.pMax.y);
Bounds2i tileBounds(Point2i(x0, y0), Point2i(x1, y1));
std::unique_ptr<FilmTile> filmTile =
camera->film->GetFilmTile(tileBounds);
for (Point2i pPixel : tileBounds) {
tileSampler->StartPixel(pPixel);
if (!InsideExclusive(pPixel, pixelBounds))
continue;
do {
// Generate a single sample using BDPT
Point2f pFilm = (Point2f)pPixel + tileSampler->Get2D();
// Trace the camera subpath
Vertex *cameraVertices = arena.Alloc<Vertex>(maxDepth + 2);
Vertex *lightVertices = arena.Alloc<Vertex>(maxDepth + 1);
int nCamera = GenerateCameraSubpath(
scene, *tileSampler, arena, maxDepth + 2, *camera,
pFilm, cameraVertices);
// Get a distribution for sampling the light at the
// start of the light subpath. Because the light path
// follows multiple bounces, basing the sampling
// distribution on any of the vertices of the camera
// path is unlikely to be a good strategy. We use the
// PowerLightDistribution by default here, which
// doesn't use the point passed to it.
const Distribution1D *lightDistr =
lightDistribution->Lookup(cameraVertices[0].p());
// Now trace the light subpath
int nLight = GenerateLightSubpath(
scene, *tileSampler, arena, maxDepth + 1,
cameraVertices[0].time(), *lightDistr, lightToIndex,
lightVertices);
// Execute all BDPT connection strategies
Spectrum L(0.f);
for (int t = 1; t <= nCamera; ++t) {
for (int s = 0; s <= nLight; ++s) {
int depth = t + s - 2;
if ((s == 1 && t == 1) || depth < 0 ||
depth > maxDepth)
continue;
// Execute the $(s, t)$ connection strategy and
// update _L_
Point2f pFilmNew = pFilm;
Float misWeight = 0.f;
Spectrum Lpath = ConnectBDPT(
scene, lightVertices, cameraVertices, s, t,
*lightDistr, lightToIndex, *camera, *tileSampler,
&pFilmNew, &misWeight);
VLOG(2) << "Connect bdpt s: " << s <<", t: " << t <<
", Lpath: " << Lpath << ", misWeight: " << misWeight;
if (visualizeStrategies || visualizeWeights) {
Spectrum value;
if (visualizeStrategies)
value =
misWeight == 0 ? 0 : Lpath / misWeight;
if (visualizeWeights) value = Lpath;
weightFilms[BufferIndex(s, t)]->AddSplat(
pFilmNew, value);
}
if (t != 1)
L += Lpath;
else
film->AddSplat(pFilmNew, Lpath);
}
}
VLOG(2) << "Add film sample pFilm: " << pFilm << ", L: " << L <<
", (y: " << L.y() << ")";
filmTile->AddSample(pFilm, L);
arena.Reset();
} while (tileSampler->StartNextSample());
}
film->MergeFilmTile(std::move(filmTile));
reporter.Update();
}, Point2i(nXTiles, nYTiles));
reporter.Done();
}
film->WriteImage(1.0f / sampler->samplesPerPixel);
// Write buffers for debug visualization
if (visualizeStrategies || visualizeWeights) {
const Float invSampleCount = 1.0f / sampler->samplesPerPixel;
for (size_t i = 0; i < weightFilms.size(); ++i)
if (weightFilms[i]) weightFilms[i]->WriteImage(invSampleCount);
}
}
