void MLTTask::Run() {
PBRT_MLT_STARTED_MLT_TASK(this);
// Declare basic _MLTTask_ variables and prepare for sampling
PBRT_MLT_STARTED_TASK_INIT();
uint32_t nPixels = (x1-x0) * (y1-y0);
uint32_t nPixelSamples = renderer->nPixelSamples;
uint32_t largeStepRate = nPixelSamples / renderer->largeStepsPerPixel;
Assert(largeStepRate > 1);
uint64_t nTaskSamples = uint64_t(nPixels) * uint64_t(largeStepRate);
uint32_t consecutiveRejects = 0;
uint32_t progressCounter = progressUpdateFrequency;
// Declare variables for storing and computing MLT samples
MemoryArena arena;
RNG rng(taskNum);
vector<PathVertex> cameraPath(renderer->maxDepth, PathVertex());
vector<PathVertex> lightPath(renderer->maxDepth, PathVertex());
vector<MLTSample> samples(2, MLTSample(renderer->maxDepth));
Spectrum L[2];
float I[2];
uint32_t current = 0, proposed = 1;
// Compute _L[current]_ for initial sample
samples[current] = initialSample;
L[current] = renderer->PathL(initialSample, scene, arena, camera,
lightDistribution, &cameraPath[0], &lightPath[0], rng);
I[current] = ::I(L[current]);
arena.FreeAll();
// Compute randomly permuted table of pixel indices for large steps
uint32_t pixelNumOffset = 0;
vector<int> largeStepPixelNum;
largeStepPixelNum.reserve(nPixels);
for (uint32_t i = 0; i < nPixels; ++i) largeStepPixelNum.push_back(i);
Shuffle(&largeStepPixelNum[0], nPixels, 1, rng);
PBRT_MLT_FINISHED_TASK_INIT();
for (uint64_t s = 0; s < nTaskSamples; ++s) {
// Compute proposed mutation to current sample
PBRT_MLT_STARTED_MUTATION();
samples[proposed] = samples[current];
bool largeStep = ((s % largeStepRate) == 0);
if (largeStep) {
int x = x0 + largeStepPixelNum[pixelNumOffset] % (x1 - x0);
int y = y0 + largeStepPixelNum[pixelNumOffset] / (x1 - x0);
LargeStep(rng, &samples[proposed], renderer->maxDepth,
x + dx, y + dy, t0, t1, renderer->bidirectional);
++pixelNumOffset;
}
else
SmallStep(rng, &samples[proposed], renderer->maxDepth,
x0, x1, y0, y1, t0, t1, renderer->bidirectional);
PBRT_MLT_FINISHED_MUTATION();
// Compute contribution of proposed sample
L[proposed] = renderer->PathL(samples[proposed], scene, arena, camera,
lightDistribution, &cameraPath[0], &lightPath[0], rng);
I[proposed] = ::I(L[proposed]);
arena.FreeAll();
// Compute acceptance probability for proposed sample
float a = min(1.f, I[proposed] / I[current]);
// Splat current and proposed samples to _Film_
PBRT_MLT_STARTED_SAMPLE_SPLAT();
if (I[current] > 0.f) {
if (!isinf(1.f / I[current])) {
Spectrum contrib = (b / nPixelSamples) * L[current] / I[current];
camera->film->Splat(samples[current].cameraSample,
(1.f - a) * contrib);
}
}
if (I[proposed] > 0.f) {
if (!isinf(1.f / I[proposed])) {
Spectrum contrib = (b / nPixelSamples) * L[proposed] / I[proposed];
camera->film->Splat(samples[proposed].cameraSample,
a * contrib);
}
}
PBRT_MLT_FINISHED_SAMPLE_SPLAT();
// Randomly accept proposed path mutation (or not)
if (consecutiveRejects >= renderer->maxConsecutiveRejects ||
rng.RandomFloat() < a) {
PBRT_MLT_ACCEPTED_MUTATION(a, &samples[current], &samples[proposed]);
current ^= 1;
proposed ^= 1;
consecutiveRejects = 0;
}
else
{
PBRT_MLT_REJECTED_MUTATION(a, &samples[current], &samples[proposed]);
++consecutiveRejects;
}
if (--progressCounter == 0) {
progress.Update();
progressCounter = progressUpdateFrequency;
}
}
Assert(pixelNumOffset == nPixels);
// Update display for recently computed Metropolis samples
PBRT_MLT_STARTED_DISPLAY_UPDATE();
int ntf = AtomicAdd(&renderer->nTasksFinished, 1);
int64_t totalSamples = int64_t(nPixels) * int64_t(nPixelSamples);
float splatScale = float(double(totalSamples) / double(ntf * nTaskSamples));
camera->film->UpdateDisplay(x0, y0, x1, y1, splatScale);
if ((taskNum % 8) == 0) {
MutexLock lock(*filmMutex);
camera->film->WriteImage(splatScale);
}
PBRT_MLT_FINISHED_DISPLAY_UPDATE();
PBRT_MLT_FINISHED_MLT_TASK(this);
}
void MLTTask::Run() {
PBRT_MLT_STARTED_MLT_TASK(this);
// Declare basic _MLTTask_ variables and prepare for sampling
RNG rng(taskNum);
MemoryArena arena;
vector<MLTSample> mltSamples(2, MLTSample(maxDepth));
Spectrum sampleLs[2];
uint32_t currentSample = 0, proposedSample = 1;
mltSamples[currentSample] = initialSample;
sampleLs[currentSample] = L(scene, renderer, camera, arena, rng, maxDepth,
ignoreDirect, mltSamples[currentSample]);
int consecutiveRejects = 0;
for (int sampleNum = 0; sampleNum < nSamples; ++sampleNum) {
// Compute proposed mutation to current sample
bool largeStep = rng.RandomFloat() < largeStepProbability;
mltSamples[proposedSample] = mltSamples[currentSample];
if (largeStep)
LargeStep(rng, &mltSamples[proposedSample], maxDepth,
x0, x1, y0, y1, t0, t1);
else
SmallStep(rng, &mltSamples[proposedSample], maxDepth,
x0, x1, y0, y1, t0, t1);
// Compute contribution of proposed sample and acceptance probability
sampleLs[proposedSample] = L(scene, renderer, camera, arena, rng, maxDepth,
ignoreDirect, mltSamples[proposedSample]);
float currentI = I(sampleLs[currentSample], mltSamples[currentSample]);
float proposedI = I(sampleLs[proposedSample], mltSamples[proposedSample]);
float a = min(1.f, proposedI / currentI);
float currentWeight = (1.f - a) /
(currentI / b + largeStepProbability) *
float(nPixels) / float(totalSamples);
float proposedWeight = (a + (largeStep ? 1.f : 0.f)) /
(proposedI / b + largeStepProbability) *
float(nPixels) / float(totalSamples);
// Splat current and proposed samples to _Film_
if (currentWeight > 0.f && currentI > 0.f)
camera->film->Splat(mltSamples[currentSample].cameraSample,
sampleLs[currentSample] * currentWeight);
if (proposedWeight > 0.f && proposedI > 0.f)
camera->film->Splat(mltSamples[proposedSample].cameraSample,
sampleLs[proposedSample] * proposedWeight);
// Randomly accept proposed path mutation (or not)
if (consecutiveRejects >= maxConsecutiveRejects ||
rng.RandomFloat() < a) {
PBRT_MLT_ACCEPTED_MUTATION(a, &mltSamples[currentSample], &mltSamples[proposedSample]);
currentSample ^= 1;
proposedSample ^= 1;
consecutiveRejects = 0;
}
else {
PBRT_MLT_REJECTED_MUTATION(a, &mltSamples[currentSample], &mltSamples[proposedSample]);
++consecutiveRejects;
}
arena.FreeAll();
}
// Update display for recently computed Metropolis samples
float nf = AtomicAdd(nSamplesFinished, nSamples);
float splatScale = float(totalSamples)/nf;
camera->film->UpdateDisplay(x0, y0, x1, y1, splatScale);
if ((taskNum % 32) == 0) {
MutexLock lock(*filmMutex);
camera->film->WriteImage(splatScale);
}
progress.Update();
PBRT_MLT_FINISHED_MLT_TASK(this);
}
void MetropolisRenderer::Render(const Scene *scene) {
PBRT_MLT_STARTED_RENDERING();
if (scene->lights.size() > 0) {
int x0, x1, y0, y1;
camera->film->GetPixelExtent(&x0, &x1, &y0, &y1);
float t0 = camera->shutterOpen, t1 = camera->shutterClose;
Distribution1D *lightDistribution = ComputeLightSamplingCDF(scene);
if (directLighting != NULL) {
PBRT_MLT_STARTED_DIRECTLIGHTING();
// Compute direct lighting before Metropolis light transport
if (nDirectPixelSamples > 0) {
LDSampler sampler(x0, x1, y0, y1, nDirectPixelSamples, t0, t1);
Sample *sample = new Sample(&sampler, directLighting, NULL, scene);
vector<Task *> directTasks;
int nDirectTasks = max(32 * NumSystemCores(),
(camera->film->xResolution * camera->film->yResolution) / (16*16));
nDirectTasks = RoundUpPow2(nDirectTasks);
ProgressReporter directProgress(nDirectTasks, "Direct Lighting");
for (int i = 0; i < nDirectTasks; ++i)
directTasks.push_back(new SamplerRendererTask(scene, this, camera, directProgress,
&sampler, sample, false, i, nDirectTasks));
std::reverse(directTasks.begin(), directTasks.end());
EnqueueTasks(directTasks);
WaitForAllTasks();
for (uint32_t i = 0; i < directTasks.size(); ++i)
delete directTasks[i];
delete sample;
directProgress.Done();
}
camera->film->WriteImage();
PBRT_MLT_FINISHED_DIRECTLIGHTING();
}
// Take initial set of samples to compute $b$
PBRT_MLT_STARTED_BOOTSTRAPPING(nBootstrap);
RNG rng(0);
MemoryArena arena;
vector<float> bootstrapI;
vector<PathVertex> cameraPath(maxDepth, PathVertex());
vector<PathVertex> lightPath(maxDepth, PathVertex());
float sumI = 0.f;
bootstrapI.reserve(nBootstrap);
MLTSample sample(maxDepth);
for (uint32_t i = 0; i < nBootstrap; ++i) {
// Generate random sample and path radiance for MLT bootstrapping
float x = Lerp(rng.RandomFloat(), x0, x1);
float y = Lerp(rng.RandomFloat(), y0, y1);
LargeStep(rng, &sample, maxDepth, x, y, t0, t1, bidirectional);
Spectrum L = PathL(sample, scene, arena, camera, lightDistribution,
&cameraPath[0], &lightPath[0], rng);
// Compute contribution for random sample for MLT bootstrapping
float I = ::I(L);
sumI += I;
bootstrapI.push_back(I);
arena.FreeAll();
}
float b = sumI / nBootstrap;
PBRT_MLT_FINISHED_BOOTSTRAPPING(b);
Info("MLT computed b = %f", b);
// Select initial sample from bootstrap samples
float contribOffset = rng.RandomFloat() * sumI;
rng.Seed(0);
sumI = 0.f;
MLTSample initialSample(maxDepth);
for (uint32_t i = 0; i < nBootstrap; ++i) {
float x = Lerp(rng.RandomFloat(), x0, x1);
float y = Lerp(rng.RandomFloat(), y0, y1);
LargeStep(rng, &initialSample, maxDepth, x, y, t0, t1,
bidirectional);
sumI += bootstrapI[i];
if (sumI > contribOffset)
break;
}
// Launch tasks to generate Metropolis samples
uint32_t nTasks = largeStepsPerPixel;
uint32_t largeStepRate = nPixelSamples / largeStepsPerPixel;
Info("MLT running %d tasks, large step rate %d", nTasks, largeStepRate);
ProgressReporter progress(nTasks * largeStepRate, "Metropolis");
vector<Task *> tasks;
Mutex *filmMutex = Mutex::Create();
Assert(IsPowerOf2(nTasks));
uint32_t scramble[2] = { rng.RandomUInt(), rng.RandomUInt() };
uint32_t pfreq = (x1-x0) * (y1-y0);
for (uint32_t i = 0; i < nTasks; ++i) {
float d[2];
Sample02(i, scramble, d);
tasks.push_back(new MLTTask(progress, pfreq, i,
d[0], d[1], x0, x1, y0, y1, t0, t1, b, initialSample,
scene, camera, this, filmMutex, lightDistribution));
}
EnqueueTasks(tasks);
WaitForAllTasks();
for (uint32_t i = 0; i < tasks.size(); ++i)
delete tasks[i];
progress.Done();
Mutex::Destroy(filmMutex);
delete lightDistribution;
}
camera->film->WriteImage();
PBRT_MLT_FINISHED_RENDERING();
}
void MetropolisRenderer::Render(const Scene *scene) {
int x0, x1, y0, y1;
camera->film->GetPixelExtent(&x0, &x1, &y0, &y1);
int nPixels = (x1-x0) * (y1-y0);
float t0 = camera->shutterOpen;
float t1 = camera->shutterClose;
if (doDirectSeparately) {
// Compute direct lighting before Metropolis light transport
LDSampler sampler(x0, x1, y0, y1, directPixelSamples, t0, t1);
Sample *sample = new Sample(&sampler, directLighting, NULL, scene);
vector<Task *> directTasks;
int nDirectTasks = max(32 * NumSystemCores(),
(camera->film->xResolution * camera->film->yResolution) / (16*16));
nDirectTasks = RoundUpPow2(nDirectTasks);
ProgressReporter directProgress(nDirectTasks, "Direct Lighting");
for (int i = 0; i < nDirectTasks; ++i)
directTasks.push_back(new SamplerRendererTask(scene, this, camera,
&sampler, directProgress, sample, i, nDirectTasks));
std::reverse(directTasks.begin(), directTasks.end());
EnqueueTasks(directTasks);
WaitForAllTasks();
for (uint32_t i = 0; i < directTasks.size(); ++i)
delete directTasks[i];
delete sample;
directProgress.Done();
}
// Take initial set of samples to compute $b$
RNG rng(0);
MemoryArena arena;
vector<float> bootstrapSamples;
float sumContrib = 0.f;
bootstrapSamples.reserve(nBootstrap);
MLTSample sample(maxDepth);
for (int i = 0; i < nBootstrap; ++i) {
// Compute contribution for random sample for MLT bootstrapping
LargeStep(rng, &sample, maxDepth, x0, x1, y0, y1, t0, t1);
float contrib = I(L(scene, this, camera, arena, rng, maxDepth,
doDirectSeparately, sample), sample);
sumContrib += contrib;
bootstrapSamples.push_back(contrib);
arena.FreeAll();
}
float b = sumContrib / nBootstrap;
// Select initial sample from bootstrap samples
rng.Seed(0);
float contribOffset = rng.RandomFloat() * sumContrib;
sumContrib = 0.f;
MLTSample initialSample(maxDepth);
for (int i = 0; i < nBootstrap; ++i) {
LargeStep(rng, &initialSample, maxDepth, x0, x1, y0, y1, t0, t1);
sumContrib += bootstrapSamples[i];
if (contribOffset < sumContrib)
break;
}
// Launch tasks to generate Metropolis samples
if (scene->lights.size() > 0) {
int nTasks = int(nSamples / 50000);
nTasks = max(nTasks, 32 * NumSystemCores());
nTasks = min(nTasks, 32768);
nSamples = (nSamples / nTasks) * nTasks;
ProgressReporter progress(nTasks, "Metropolis");
vector<Task *> tasks;
Mutex *filmMutex = Mutex::Create();
for (int i = 0; i < nTasks; ++i)
tasks.push_back(new MLTTask(progress, i, int(nSamples/nTasks), nSamples,
nPixels, x0, x1, y0, y1, t0, t1, b, largeStepProbability, initialSample,
doDirectSeparately, maxConsecutiveRejects, maxDepth, scene, camera, this,
&nSamplesFinished, filmMutex));
EnqueueTasks(tasks);
WaitForAllTasks();
for (uint32_t i = 0; i < tasks.size(); ++i)
delete tasks[i];
progress.Done();
}
camera->film->WriteImage();
}
