void PhotonShootingTask::Run() {
// Declare local variables for _PhotonShootingTask_
MemoryArena arena;
RNG rng(31 * taskNum);
vector<Photon> localDirectPhotons, localIndirectPhotons, localCausticPhotons;
vector<RadiancePhoton> localRadiancePhotons;
uint32_t totalPaths = 0;
bool causticDone = (integrator->nCausticPhotonsWanted == 0);
bool indirectDone = (integrator->nIndirectPhotonsWanted == 0);
PermutedHalton halton(6, rng);
vector<Spectrum> localRpReflectances, localRpTransmittances;
while (true) {
// Follow photon paths for a block of samples
const uint32_t blockSize = 4096;
for (uint32_t i = 0; i < blockSize; ++i) {
float u[6];
halton.Sample(++totalPaths, u);
// Choose light to shoot photon from
float lightPdf;
int lightNum = lightDistribution->SampleDiscrete(u[0], &lightPdf);
const Light *light = scene->lights[lightNum];
// Generate _photonRay_ from light source and initialize _alpha_
RayDifferential photonRay;
float pdf;
LightSample ls(u[1], u[2], u[3]);
Normal Nl;
Spectrum Le = light->Sample_L(scene, ls, u[4], u[5],
time, &photonRay, &Nl, &pdf);
if (pdf == 0.f || Le.IsBlack()) continue;
Spectrum alpha = (AbsDot(Nl, photonRay.d) * Le) / (pdf * lightPdf);
if (!alpha.IsBlack()) {
// Follow photon path through scene and record intersections
PBRT_PHOTON_MAP_STARTED_RAY_PATH(&photonRay, &alpha);
bool specularPath = true;
Intersection photonIsect;
int nIntersections = 0;
while (scene->Intersect(photonRay, &photonIsect)) {
++nIntersections;
// Handle photon/surface intersection
alpha *= renderer->Transmittance(scene, photonRay, NULL, rng, arena);
BSDF *photonBSDF = photonIsect.GetBSDF(photonRay, arena);
BxDFType specularType = BxDFType(BSDF_REFLECTION |
BSDF_TRANSMISSION | BSDF_SPECULAR);
bool hasNonSpecular = (photonBSDF->NumComponents() >
photonBSDF->NumComponents(specularType));
Vector wo = -photonRay.d;
if (hasNonSpecular) {
// Deposit photon at surface
Photon photon(photonIsect.dg.p, alpha, wo);
bool depositedPhoton = false;
if (specularPath && nIntersections > 1) {
if (!causticDone) {
PBRT_PHOTON_MAP_DEPOSITED_CAUSTIC_PHOTON(&photonIsect.dg, &alpha, &wo);
depositedPhoton = true;
localCausticPhotons.push_back(photon);
}
}
else {
// Deposit either direct or indirect photon
// stop depositing direct photons once indirectDone is true; don't
// want to waste memory storing too many if we're going a long time
// trying to get enough caustic photons desposited.
if (nIntersections == 1 && !indirectDone && integrator->finalGather) {
PBRT_PHOTON_MAP_DEPOSITED_DIRECT_PHOTON(&photonIsect.dg, &alpha, &wo);
depositedPhoton = true;
localDirectPhotons.push_back(photon);
}
else if (nIntersections > 1 && !indirectDone) {
PBRT_PHOTON_MAP_DEPOSITED_INDIRECT_PHOTON(&photonIsect.dg, &alpha, &wo);
depositedPhoton = true;
localIndirectPhotons.push_back(photon);
}
}
// Possibly create radiance photon at photon intersection point
if (depositedPhoton && integrator->finalGather &&
rng.RandomFloat() < .125f) {
Normal n = photonIsect.dg.nn;
n = Faceforward(n, -photonRay.d);
localRadiancePhotons.push_back(RadiancePhoton(photonIsect.dg.p, n));
Spectrum rho_r = photonBSDF->rho(rng, BSDF_ALL_REFLECTION);
localRpReflectances.push_back(rho_r);
Spectrum rho_t = photonBSDF->rho(rng, BSDF_ALL_TRANSMISSION);
localRpTransmittances.push_back(rho_t);
}
}
if (nIntersections >= integrator->maxPhotonDepth) break;
// Sample new photon ray direction
Vector wi;
float pdf;
BxDFType flags;
Spectrum fr = photonBSDF->Sample_f(wo, &wi, BSDFSample(rng),
&pdf, BSDF_ALL, &flags);
if (fr.IsBlack() || pdf == 0.f) break;
Spectrum anew = alpha * fr *
AbsDot(wi, photonBSDF->dgShading.nn) / pdf;
// Possibly terminate photon path with Russian roulette
float continueProb = min(1.f, anew.y() / alpha.y());
if (rng.RandomFloat() > continueProb)
break;
alpha = anew / continueProb;
specularPath &= ((flags & BSDF_SPECULAR) != 0);
if (indirectDone && !specularPath) break;
photonRay = RayDifferential(photonIsect.dg.p, wi, photonRay,
photonIsect.rayEpsilon);
}
PBRT_PHOTON_MAP_FINISHED_RAY_PATH(&photonRay, &alpha);
}
arena.FreeAll();
}
// Merge local photon data with data in _PhotonIntegrator_
{ MutexLock lock(mutex);
// Give up if we're not storing enough photons
if (abortTasks)
return;
if (nshot > 500000 &&
(unsuccessful(integrator->nCausticPhotonsWanted,
causticPhotons.size(), blockSize) ||
unsuccessful(integrator->nIndirectPhotonsWanted,
indirectPhotons.size(), blockSize))) {
Error("Unable to store enough photons. Giving up.\n");
causticPhotons.erase(causticPhotons.begin(), causticPhotons.end());
indirectPhotons.erase(indirectPhotons.begin(), indirectPhotons.end());
radiancePhotons.erase(radiancePhotons.begin(), radiancePhotons.end());
abortTasks = true;
return;
}
progress.Update(localIndirectPhotons.size() + localCausticPhotons.size());
nshot += blockSize;
// Merge indirect photons into shared array
if (!indirectDone) {
integrator->nIndirectPaths += blockSize;
for (uint32_t i = 0; i < localIndirectPhotons.size(); ++i)
indirectPhotons.push_back(localIndirectPhotons[i]);
localIndirectPhotons.erase(localIndirectPhotons.begin(),
localIndirectPhotons.end());
if (indirectPhotons.size() >= integrator->nIndirectPhotonsWanted)
indirectDone = true;
nDirectPaths += blockSize;
for (uint32_t i = 0; i < localDirectPhotons.size(); ++i)
directPhotons.push_back(localDirectPhotons[i]);
localDirectPhotons.erase(localDirectPhotons.begin(),
localDirectPhotons.end());
}
// Merge direct, caustic, and radiance photons into shared array
if (!causticDone) {
integrator->nCausticPaths += blockSize;
for (uint32_t i = 0; i < localCausticPhotons.size(); ++i)
causticPhotons.push_back(localCausticPhotons[i]);
localCausticPhotons.erase(localCausticPhotons.begin(), localCausticPhotons.end());
if (causticPhotons.size() >= integrator->nCausticPhotonsWanted)
causticDone = true;
}
for (uint32_t i = 0; i < localRadiancePhotons.size(); ++i)
radiancePhotons.push_back(localRadiancePhotons[i]);
localRadiancePhotons.erase(localRadiancePhotons.begin(), localRadiancePhotons.end());
for (uint32_t i = 0; i < localRpReflectances.size(); ++i)
rpReflectances.push_back(localRpReflectances[i]);
localRpReflectances.erase(localRpReflectances.begin(), localRpReflectances.end());
for (uint32_t i = 0; i < localRpTransmittances.size(); ++i)
rpTransmittances.push_back(localRpTransmittances[i]);
localRpTransmittances.erase(localRpTransmittances.begin(), localRpTransmittances.end());
}
// Exit task if enough photons have been found
if (indirectDone && causticDone)
break;
}
}
void ExPhotonIntegrator::Preprocess(const Scene *scene) {
if (scene->lights.size() == 0) return;
ProgressReporter progress(nCausticPhotons+ // NOBOOK
nIndirectPhotons, "Shooting photons"); // NOBOOK
vector<Photon> causticPhotons;
vector<Photon> indirectPhotons;
vector<Photon> directPhotons;
vector<RadiancePhoton> radiancePhotons;
causticPhotons.reserve(nCausticPhotons); // NOBOOK
indirectPhotons.reserve(nIndirectPhotons); // NOBOOK
// Initialize photon shooting statistics
static StatsCounter nshot("Photon Map",
"Number of photons shot from lights");
bool causticDone = (nCausticPhotons == 0);
bool indirectDone = (nIndirectPhotons == 0);
// Compute light power CDF for photon shooting
int nLights = int(scene->lights.size());
float *lightPower = (float *)alloca(nLights * sizeof(float));
float *lightCDF = (float *)alloca((nLights+1) * sizeof(float));
for (int i = 0; i < nLights; ++i)
lightPower[i] = scene->lights[i]->Power(scene).y();
float totalPower;
ComputeStep1dCDF(lightPower, nLights, &totalPower, lightCDF);
// Declare radiance photon reflectance arrays
vector<Spectrum> rpReflectances, rpTransmittances;
while (!causticDone || !indirectDone) {
++nshot;
// Give up if we're not storing enough photons
if (nshot > 500000 &&
(unsuccessful(nCausticPhotons,
causticPhotons.size(),
nshot) ||
unsuccessful(nIndirectPhotons,
indirectPhotons.size(),
nshot))) {
Error("Unable to store enough photons. Giving up.\n");
return;
}
// Trace a photon path and store contribution
// Choose 4D sample values for photon
float u[4];
u[0] = RadicalInverse((int)nshot+1, 2);
u[1] = RadicalInverse((int)nshot+1, 3);
u[2] = RadicalInverse((int)nshot+1, 5);
u[3] = RadicalInverse((int)nshot+1, 7);
// Choose light to shoot photon from
float lightPdf;
float uln = RadicalInverse((int)nshot+1, 11);
int lightNum = Floor2Int(SampleStep1d(lightPower, lightCDF,
totalPower, nLights, uln, &lightPdf) * nLights);
lightNum = min(lightNum, nLights-1);
const Light *light = scene->lights[lightNum];
// Generate _photonRay_ from light source and initialize _alpha_
RayDifferential photonRay;
float pdf;
Spectrum alpha = light->Sample_L(scene, u[0], u[1], u[2], u[3],
&photonRay, &pdf);
if (pdf == 0.f || alpha.Black()) continue;
alpha /= pdf * lightPdf;
if (!alpha.Black()) {
// Follow photon path through scene and record intersections
bool specularPath = false;
Intersection photonIsect;
int nIntersections = 0;
while (scene->Intersect(photonRay, &photonIsect)) {
++nIntersections;
// Handle photon/surface intersection
alpha *= scene->Transmittance(photonRay);
Vector wo = -photonRay.d;
BSDF *photonBSDF = photonIsect.GetBSDF(photonRay);
BxDFType specularType = BxDFType(BSDF_REFLECTION |
BSDF_TRANSMISSION | BSDF_SPECULAR);
bool hasNonSpecular = (photonBSDF->NumComponents() >
photonBSDF->NumComponents(specularType));
if (hasNonSpecular) {
// Deposit photon at surface
Photon photon(photonIsect.dg.p, alpha, wo);
if (nIntersections == 1) {
// Deposit direct photon
directPhotons.push_back(photon);
}
else {
// Deposit either caustic or indirect photon
if (specularPath) {
// Process caustic photon intersection
if (!causticDone) {
causticPhotons.push_back(photon);
if (causticPhotons.size() == nCausticPhotons) {
causticDone = true;
nCausticPaths = (int)nshot;
causticMap = new KdTree<Photon, PhotonProcess>(causticPhotons);
}
progress.Update();
}
}
else {
// Process indirect lighting photon intersection
if (!indirectDone) {
indirectPhotons.push_back(photon);
if (indirectPhotons.size() == nIndirectPhotons) {
indirectDone = true;
nIndirectPaths = (int)nshot;
indirectMap = new KdTree<Photon, PhotonProcess>(indirectPhotons);
}
progress.Update();
}
}
}
if (finalGather && RandomFloat() < .125f) {
// Store data for radiance photon
static StatsCounter rp("Photon Map", "Radiance photons created"); // NOBOOK
++rp; // NOBOOK
Normal n = photonIsect.dg.nn;
if (Dot(n, photonRay.d) > 0.f) n = -n;
radiancePhotons.push_back(RadiancePhoton(photonIsect.dg.p, n));
Spectrum rho_r = photonBSDF->rho(BSDF_ALL_REFLECTION);
rpReflectances.push_back(rho_r);
Spectrum rho_t = photonBSDF->rho(BSDF_ALL_TRANSMISSION);
rpTransmittances.push_back(rho_t);
}
}
// Sample new photon ray direction
Vector wi;
float pdf;
BxDFType flags;
// Get random numbers for sampling outgoing photon direction
float u1, u2, u3;
if (nIntersections == 1) {
u1 = RadicalInverse((int)nshot+1, 13);
u2 = RadicalInverse((int)nshot+1, 17);
u3 = RadicalInverse((int)nshot+1, 19);
}
else {
u1 = RandomFloat();
u2 = RandomFloat();
u3 = RandomFloat();
}
// Compute new photon weight and possibly terminate with RR
Spectrum fr = photonBSDF->Sample_f(wo, &wi, u1, u2, u3,
&pdf, BSDF_ALL, &flags);
if (fr.Black() || pdf == 0.f)
break;
Spectrum anew = alpha * fr *
AbsDot(wi, photonBSDF->dgShading.nn) / pdf;
float continueProb = min(1.f, anew.y() / alpha.y());
if (RandomFloat() > continueProb || nIntersections > 10)
break;
alpha = anew / continueProb;
specularPath = (nIntersections == 1 || specularPath) &&
((flags & BSDF_SPECULAR) != 0);
photonRay = RayDifferential(photonIsect.dg.p, wi);
}
}
BSDF::FreeAll();
}
progress.Done(); // NOBOOK
// Precompute radiance at a subset of the photons
KdTree<Photon, PhotonProcess> directMap(directPhotons);
int nDirectPaths = nshot;
if (finalGather) {
ProgressReporter p2(radiancePhotons.size(), "Computing photon radiances"); // NOBOOK
for (u_int i = 0; i < radiancePhotons.size(); ++i) {
// Compute radiance for radiance photon _i_
RadiancePhoton &rp = radiancePhotons[i];
const Spectrum &rho_r = rpReflectances[i];
const Spectrum &rho_t = rpTransmittances[i];
Spectrum E;
Point p = rp.p;
Normal n = rp.n;
if (!rho_r.Black()) {
E = estimateE(&directMap, nDirectPaths, p, n) +
estimateE(indirectMap, nIndirectPaths, p, n) +
estimateE(causticMap, nCausticPaths, p, n);
rp.Lo += E * INV_PI * rho_r;
}
if (!rho_t.Black()) {
E = estimateE(&directMap, nDirectPaths, p, -n) +
estimateE(indirectMap, nIndirectPaths, p, -n) +
estimateE(causticMap, nCausticPaths, p, -n);
rp.Lo += E * INV_PI * rho_t;
}
p2.Update(); // NOBOOK
}
radianceMap = new KdTree<RadiancePhoton,
RadiancePhotonProcess>(radiancePhotons);
p2.Done(); // NOBOOK
}
}