PowerLightDistribution::PowerLightDistribution(const Scene &scene)
: distrib(ComputeLightPowerDistribution(scene)) {}
void MLTIntegrator::Render(const Scene &scene) {
ProfilePhase p(Prof::IntegratorRender);
std::unique_ptr<Distribution1D> lightDistr =
ComputeLightPowerDistribution(scene);
// Generate bootstrap samples and compute normalization constant $b$
int nBootstrapSamples = nBootstrap * (maxDepth + 1);
std::vector<Float> bootstrapWeights(nBootstrapSamples, 0);
if (scene.lights.size() > 0) {
ProgressReporter progress(nBootstrap / 256,
"Generating bootstrap paths");
std::vector<MemoryArena> bootstrapThreadArenas(MaxThreadIndex());
int chunkSize = Clamp(nBootstrap / 128, 1, 8192);
ParallelFor([&](int i) {
// Generate _i_th bootstrap sample
MemoryArena &arena = bootstrapThreadArenas[threadIndex];
for (int depth = 0; depth <= maxDepth; ++depth) {
int rngIndex = i * (maxDepth + 1) + depth;
MLTSampler sampler(mutationsPerPixel, rngIndex, sigma,
largeStepProbability, nSampleStreams);
Point2f pRaster;
bootstrapWeights[rngIndex] =
L(scene, arena, lightDistr, sampler, depth, &pRaster).y();
arena.Reset();
}
if ((i + 1 % 256) == 0) progress.Update();
}, nBootstrap, chunkSize);
progress.Done();
}
Distribution1D bootstrap(&bootstrapWeights[0], nBootstrapSamples);
Float b = bootstrap.funcInt * (maxDepth + 1);
// Run _nChains_ Markov chains in parallel
Film &film = *camera->film;
int64_t nTotalMutations =
(int64_t)mutationsPerPixel * (int64_t)film.GetSampleBounds().Area();
if (scene.lights.size() > 0) {
StatTimer timer(&renderingTime);
const int progressFrequency = 32768;
ProgressReporter progress(nTotalMutations / progressFrequency,
"Rendering");
ParallelFor([&](int i) {
int64_t nChainMutations =
std::min((i + 1) * nTotalMutations / nChains, nTotalMutations) -
i * nTotalMutations / nChains;
// Follow {i}th Markov chain for _nChainMutations_
MemoryArena arena;
// Select initial state from the set of bootstrap samples
RNG rng(i);
int bootstrapIndex = bootstrap.SampleDiscrete(rng.UniformFloat());
int depth = bootstrapIndex % (maxDepth + 1);
// Initialize local variables for selected state
MLTSampler sampler(mutationsPerPixel, bootstrapIndex, sigma,
largeStepProbability, nSampleStreams);
Point2f pCurrent;
Spectrum LCurrent =
L(scene, arena, lightDistr, sampler, depth, &pCurrent);
// Run the Markov chain for _nChainMutations_ steps
for (int64_t j = 0; j < nChainMutations; ++j) {
sampler.StartIteration();
Point2f pProposed;
Spectrum LProposed =
L(scene, arena, lightDistr, sampler, depth, &pProposed);
// Compute acceptance probability for proposed sample
Float accept = std::min((Float)1, LProposed.y() / LCurrent.y());
// Splat both current and proposed samples to _film_
if (accept > 0)
film.AddSplat(pProposed,
LProposed * accept / LProposed.y());
film.AddSplat(pCurrent, LCurrent * (1 - accept) / LCurrent.y());
// Accept or reject the proposal
if (rng.UniformFloat() < accept) {
pCurrent = pProposed;
LCurrent = LProposed;
sampler.Accept();
++acceptedMutations;
} else
sampler.Reject();
++totalMutations;
if ((i * nTotalMutations / nChains + j) % progressFrequency ==
0)
progress.Update();
arena.Reset();
}
}, nChains);
progress.Done();
}
// Store final image computed with MLT
camera->film->WriteImage(b / mutationsPerPixel);
}
void BDPTIntegrator::Render(const Scene &scene) {
ProfilePhase p(Prof::IntegratorRender);
// Compute _lightDistr_ for sampling lights proportional to power
std::unique_ptr<Distribution1D> lightDistr =
ComputeLightPowerDistribution(scene);
// 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) {
StatTimer timer(&renderingTime);
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 and light subpaths
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);
int nLight = GenerateLightSubpath(
scene, *tileSampler, arena, maxDepth + 1,
cameraVertices[0].time(), *lightDistr, 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, *camera, *tileSampler, &pFilmNew,
&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);
}
}
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);
}
}
