void Fluence2ParticleTracer::handleSurfaceInteraction(int depth, int nullInteractions,
bool caustic, const Intersection &its, const Medium *medium, const Spectrum &weight)
{
if ( its.isMediumTransition() && its.wi.z < 0.0f )
{
m_result->putSurface(its.p, weight);
}
}
void CaptureParticleWorker::handleSurfaceInteraction(int depth,
bool caustic, const Intersection &its, const Medium *medium,
const Spectrum &weight) {
const ProjectiveCamera *camera = static_cast<const ProjectiveCamera *>(m_camera.get());
Point2 screenSample;
if (camera->positionToSample(its.p, screenSample)) {
Point cameraPosition = camera->getPosition(screenSample);
Float t = dot(camera->getImagePlaneNormal(), its.p-cameraPosition);
if (t < camera->getNearClip() || t > camera->getFarClip())
return;
if (its.isMediumTransition())
medium = its.getTargetMedium(cameraPosition - its.p);
Spectrum transmittance = m_scene->getTransmittance(its.p,
cameraPosition, its.time, medium);
if (transmittance.isZero())
return;
const BSDF *bsdf = its.shape->getBSDF();
Vector wo = cameraPosition - its.p;
Float dist = wo.length(); wo /= dist;
BSDFQueryRecord bRec(its, its.toLocal(wo));
bRec.quantity = EImportance;
Float importance;
if (m_isPerspectiveCamera)
importance = ((const PerspectiveCamera *) camera)->importance(screenSample) / (dist * dist);
else
importance = 1/camera->areaDensity(screenSample);
Vector wi = its.toWorld(its.wi);
/* Prevent light leaks due to the use of shading normals -- [Veach, p. 158] */
Float wiDotGeoN = dot(its.geoFrame.n, wi),
woDotGeoN = dot(its.geoFrame.n, wo);
if (wiDotGeoN * Frame::cosTheta(bRec.wi) <= 0 ||
woDotGeoN * Frame::cosTheta(bRec.wo) <= 0)
return;
/* Adjoint BSDF for shading normals -- [Veach, p. 155] */
Float correction = std::abs(
(Frame::cosTheta(bRec.wi) * woDotGeoN)/
(Frame::cosTheta(bRec.wo) * wiDotGeoN));
/* Splat onto the accumulation buffer */
Ray ray(its.p, wo, 0, dist, its.time);
Spectrum sampleVal = weight * bsdf->fCos(bRec)
* transmittance * (importance * correction);
m_workResult->splat(screenSample, sampleVal, m_filter);
}
}
void ParticleTracer::process(const WorkUnit *workUnit, WorkResult *workResult,
const bool &stop) {
const RangeWorkUnit *range = static_cast<const RangeWorkUnit *>(workUnit);
MediumSamplingRecord mRec;
Intersection its;
ref<Sensor> sensor = m_scene->getSensor();
bool needsTimeSample = sensor->needsTimeSample();
PositionSamplingRecord pRec(sensor->getShutterOpen()
+ 0.5f * sensor->getShutterOpenTime());
Ray ray;
m_sampler->generate(Point2i(0));
for (size_t index = range->getRangeStart(); index <= range->getRangeEnd() && !stop; ++index) {
m_sampler->setSampleIndex(index);
/* Sample an emission */
if (needsTimeSample)
pRec.time = sensor->sampleTime(m_sampler->next1D());
const Emitter *emitter = NULL;
const Medium *medium;
Spectrum power;
Ray ray;
if (m_emissionEvents) {
/* Sample the position and direction component separately to
generate emission events */
power = m_scene->sampleEmitterPosition(pRec, m_sampler->next2D());
emitter = static_cast<const Emitter *>(pRec.object);
medium = emitter->getMedium();
/* Forward the sampling event to the attached handler */
handleEmission(pRec, medium, power);
DirectionSamplingRecord dRec;
power *= emitter->sampleDirection(dRec, pRec,
emitter->needsDirectionSample() ? m_sampler->next2D() : Point2(0.5f));
ray.setTime(pRec.time);
ray.setOrigin(pRec.p);
ray.setDirection(dRec.d);
} else {
/* Sample both components together, which is potentially
faster / uses a better sampling strategy */
power = m_scene->sampleEmitterRay(ray, emitter,
m_sampler->next2D(), m_sampler->next2D(), pRec.time);
medium = emitter->getMedium();
handleNewParticle();
}
int depth = 1, nullInteractions = 0;
bool delta = false;
Spectrum throughput(1.0f); // unitless path throughput (used for russian roulette)
while (!throughput.isZero() && (depth <= m_maxDepth || m_maxDepth < 0)) {
m_scene->rayIntersectAll(ray, its);
/* ==================================================================== */
/* Radiative Transfer Equation sampling */
/* ==================================================================== */
if (medium && medium->sampleDistance(Ray(ray, 0, its.t), mRec, m_sampler)) {
/* Sample the integral
\int_x^y tau(x, x') [ \sigma_s \int_{S^2} \rho(\omega,\omega') L(x,\omega') d\omega' ] dx'
*/
throughput *= mRec.sigmaS * mRec.transmittance / mRec.pdfSuccess;
/* Forward the medium scattering event to the attached handler */
handleMediumInteraction(depth, nullInteractions,
delta, mRec, medium, -ray.d, throughput*power);
PhaseFunctionSamplingRecord pRec(mRec, -ray.d, EImportance);
throughput *= medium->getPhaseFunction()->sample(pRec, m_sampler);
delta = false;
ray = Ray(mRec.p, pRec.wo, ray.time);
ray.mint = 0;
} else if (its.t == std::numeric_limits<Float>::infinity()) {
/* There is no surface in this direction */
break;
} else {
/* Sample
tau(x, y) (Surface integral). This happens with probability mRec.pdfFailure
Account for this and multiply by the proper per-color-channel transmittance.
*/
if (medium)
throughput *= mRec.transmittance / mRec.pdfFailure;
const BSDF *bsdf = its.getBSDF();
/* Forward the surface scattering event to the attached handler */
handleSurfaceInteraction(depth, nullInteractions, delta, its, medium, throughput*power);
BSDFSamplingRecord bRec(its, m_sampler, EImportance);
Spectrum bsdfWeight = bsdf->sample(bRec, m_sampler->next2D());
if (bsdfWeight.isZero())
break;
/* Prevent light leaks due to the use of shading normals -- [Veach, p. 158] */
Vector wi = -ray.d, wo = its.toWorld(bRec.wo);
Float wiDotGeoN = dot(its.geoFrame.n, wi),
woDotGeoN = dot(its.geoFrame.n, wo);
if (wiDotGeoN * Frame::cosTheta(bRec.wi) <= 0 ||
woDotGeoN * Frame::cosTheta(bRec.wo) <= 0)
break;
/* Keep track of the weight, medium and relative
refractive index along the path */
throughput *= bsdfWeight;
if (its.isMediumTransition())
medium = its.getTargetMedium(woDotGeoN);
if (bRec.sampledType & BSDF::ENull)
++nullInteractions;
else
delta = bRec.sampledType & BSDF::EDelta;
#if 0
/* This is somewhat unfortunate: for accuracy, we'd really want the
correction factor below to match the path tracing interpretation
of a scene with shading normals. However, this factor can become
extremely large, which adds unacceptable variance to output
renderings.
So for now, it is disabled. The adjoint particle tracer and the
photon mapping variants still use this factor for the last
bounce -- just not for the intermediate ones, which introduces
a small (though in practice not noticeable) amount of error. This
is also what the implementation of SPPM by Toshiya Hachisuka does.
Ultimately, we'll need better adjoint BSDF sampling strategies
that incorporate these extra terms */
/* Adjoint BSDF for shading normals -- [Veach, p. 155] */
throughput *= std::abs(
(Frame::cosTheta(bRec.wi) * woDotGeoN)/
(Frame::cosTheta(bRec.wo) * wiDotGeoN));
#endif
ray.setOrigin(its.p);
ray.setDirection(wo);
ray.mint = Epsilon;
}
if (depth++ >= m_rrDepth) {
/* Russian roulette: try to keep path weights equal to one,
Stop with at least some probability to avoid
getting stuck (e.g. due to total internal reflection) */
Float q = std::min(throughput.max(), (Float) 0.95f);
if (m_sampler->next1D() >= q)
break;
throughput /= q;
}
}
}
}
bool PathEdge::pathConnectAndCollapse(const Scene *scene, const PathEdge *predEdge,
const PathVertex *vs, const PathVertex *vt,
const PathEdge *succEdge, int &interactions) {
if (vs->isEmitterSupernode() || vt->isSensorSupernode()) {
Float radianceTransport = vt->isSensorSupernode() ? 1.0f : 0.0f,
importanceTransport = 1-radianceTransport;
medium = NULL;
length = 0.0f;
d = Vector(0.0f);
pdf[ERadiance] = radianceTransport;
pdf[EImportance] = importanceTransport;
weight[ERadiance] = Spectrum(radianceTransport);
weight[EImportance] = Spectrum(importanceTransport);
interactions = 0;
} else {
Point vsp = vs->getPosition(), vtp = vt->getPosition();
d = vsp-vtp;
length = d.length();
int maxInteractions = interactions;
interactions = 0;
if (length == 0) {
#if defined(MTS_BD_DEBUG)
SLog(EWarn, "Tried to connect %s and %s, which are located at exactly the same position!",
vs->toString().c_str(), vt->toString().c_str());
#endif
return false;
}
d /= length;
Float lengthFactor = vs->isOnSurface() ? (1-ShadowEpsilon) : 1;
Ray ray(vtp, d, vt->isOnSurface() ? Epsilon : 0, length * lengthFactor, vs->getTime());
weight[ERadiance] = Spectrum(1.0f);
weight[EImportance] = Spectrum(1.0f);
pdf[ERadiance] = 1.0f;
pdf[EImportance] = 1.0f;
Intersection its;
Float remaining = length;
medium = vt->getTargetMedium(succEdge, d);
while (true) {
bool surface = scene->rayIntersectAll(ray, its);
if (surface && (interactions == maxInteractions ||
!(its.getBSDF()->getType() & BSDF::ENull))) {
/* Encountered an occluder -- zero transmittance. */
return false;
}
if (medium) {
Float segmentLength = std::min(its.t, remaining);
MediumSamplingRecord mRec;
medium->eval(Ray(ray, 0, segmentLength), mRec);
Float pdfRadiance = (surface || !vs->isMediumInteraction())
? mRec.pdfFailure : mRec.pdfSuccess;
Float pdfImportance = (interactions > 0 || !vt->isMediumInteraction())
? mRec.pdfFailure : mRec.pdfSuccessRev;
if (pdfRadiance == 0 || pdfImportance == 0 || mRec.transmittance.isZero()) {
/* Zero transmittance */
return false;
}
weight[EImportance] *= mRec.transmittance / pdfImportance;
weight[ERadiance] *= mRec.transmittance / pdfRadiance;
pdf[EImportance] *= pdfImportance;
pdf[ERadiance] *= pdfRadiance;
}
if (!surface || remaining - its.t < 0)
break;
/* Advance the ray */
ray.o = ray(its.t);
remaining -= its.t;
ray.mint = Epsilon;
ray.maxt = remaining * lengthFactor;
/* Account for the ENull interaction */
const BSDF *bsdf = its.getBSDF();
Vector wo = its.toLocal(ray.d);
BSDFSamplingRecord bRec(its, -wo, wo, ERadiance);
bRec.component = BSDF::ENull;
Float nullPdf = bsdf->pdf(bRec, EDiscrete);
if (nullPdf == 0)
return false;
Spectrum nullWeight = bsdf->eval(bRec, EDiscrete) / nullPdf;
weight[EImportance] *= nullWeight;
weight[ERadiance] *= nullWeight;
pdf[EImportance] *= nullPdf;
pdf[ERadiance] *= nullPdf;
if (its.isMediumTransition()) {
const Medium *expected = its.getTargetMedium(-ray.d);
if (medium != expected) {
#if defined(MTS_BD_TRACE)
SLog(EWarn, "PathEdge::pathConnectAndCollapse(): attempted two connect "
"two vertices that disagree about the medium in between! "
"Please check your scene for leaks.");
#endif
++mediumInconsistencies;
return false;
}
medium = its.getTargetMedium(ray.d);
}
if (++interactions > 100) { /// Just a precaution..
SLog(EWarn, "pathConnectAndCollapse(): round-off error issues?");
return false;
}
}
if (medium != vs->getTargetMedium(predEdge, -d)) {
#if defined(MTS_BD_TRACE)
SLog(EWarn, "PathEdge::pathConnectAndCollapse(): attempted two connect "
"two vertices that disagree about the medium in between! "
"Please check your scene for leaks.");
#endif
++mediumInconsistencies;
return false;
}
}
return true;
}
bool PathEdge::pathConnect(const Scene *scene, const PathEdge *predEdge,
const PathVertex *vs, Path &result, const PathVertex *vt,
const PathEdge *succEdge, int maxInteractions, MemoryPool &pool) {
BDAssert(result.edgeCount() == 0 && result.vertexCount() == 0);
if (vs->isEmitterSupernode() || vt->isSensorSupernode()) {
Float radianceTransport = vt->isSensorSupernode() ? 1.0f : 0.0f,
importanceTransport = 1-radianceTransport;
PathEdge *edge = pool.allocEdge();
edge->medium = NULL;
edge->length = 0.0f;
edge->d = Vector(0.0f);
edge->pdf[ERadiance] = radianceTransport;
edge->pdf[EImportance] = importanceTransport;
edge->weight[ERadiance] = Spectrum(radianceTransport);
edge->weight[EImportance] = Spectrum(importanceTransport);
result.append(edge);
} else {
Point vsp = vs->getPosition(), vtp = vt->getPosition();
Vector d(vsp-vtp);
Float remaining = d.length();
d /= remaining;
if (remaining == 0) {
#if defined(MTS_BD_DEBUG)
SLog(EWarn, "Tried to connect %s and %s, which are located at exactly the same position!",
vs->toString().c_str(), vt->toString().c_str());
#endif
return false;
}
Float lengthFactor = vs->isOnSurface() ? (1-ShadowEpsilon) : 1;
Ray ray(vtp, d, vt->isOnSurface() ? Epsilon : 0,
remaining * lengthFactor, vs->getTime());
const Medium *medium = vt->getTargetMedium(succEdge, d);
int interactions = 0;
Intersection its;
while (true) {
bool surface = scene->rayIntersectAll(ray, its);
if (surface && (interactions == maxInteractions ||
!(its.getBSDF()->getType() & BSDF::ENull))) {
/* Encountered an occluder -- zero transmittance. */
result.release(pool);
return false;
}
/* Construct an edge */
PathEdge *edge = pool.allocEdge();
result.append(edge);
edge->length = std::min(its.t, remaining);
edge->medium = medium;
edge->d = d;
if (medium) {
MediumSamplingRecord mRec;
medium->eval(Ray(ray, 0, edge->length), mRec);
edge->pdf[ERadiance] = (surface || !vs->isMediumInteraction())
? mRec.pdfFailure : mRec.pdfSuccess;
edge->pdf[EImportance] = (interactions > 0 || !vt->isMediumInteraction())
? mRec.pdfFailure : mRec.pdfSuccessRev;
if (edge->pdf[ERadiance] == 0 || edge->pdf[EImportance] == 0
|| mRec.transmittance.isZero()) {
/* Zero transmittance */
result.release(pool);
return false;
}
edge->weight[EImportance] = mRec.transmittance / edge->pdf[EImportance];
edge->weight[ERadiance] = mRec.transmittance / edge->pdf[ERadiance];
} else {
edge->weight[ERadiance] = edge->weight[EImportance] = Spectrum(1.0f);
edge->pdf[ERadiance] = edge->pdf[EImportance] = 1.0f;
}
if (!surface || remaining - its.t < 0)
break;
/* Advance the ray */
ray.o = ray(its.t);
remaining -= its.t;
ray.mint = Epsilon;
ray.maxt = remaining * lengthFactor;
const BSDF *bsdf = its.getBSDF();
/* Account for the ENull interaction */
Vector wo = its.toLocal(ray.d);
BSDFSamplingRecord bRec(its, -wo, wo, ERadiance);
bRec.component = BSDF::ENull;
Float nullPdf = bsdf->pdf(bRec, EDiscrete);
if (nullPdf == 0) {
result.release(pool);
return false;
}
PathVertex *vertex = pool.allocVertex();
vertex->type = PathVertex::ESurfaceInteraction;
vertex->degenerate = !(bsdf->hasComponent(BSDF::ESmooth)
|| its.shape->isEmitter() || its.shape->isSensor());
vertex->measure = EDiscrete;
vertex->componentType = BSDF::ENull;
vertex->pdf[EImportance] = vertex->pdf[ERadiance] = nullPdf;
vertex->weight[EImportance] = vertex->weight[ERadiance]
= bsdf->eval(bRec, EDiscrete) / nullPdf;
vertex->rrWeight = 1.0f;
vertex->getIntersection() = its;
result.append(vertex);
if (its.isMediumTransition()) {
const Medium *expected = its.getTargetMedium(-ray.d);
if (medium != expected) {
#if defined(MTS_BD_TRACE)
SLog(EWarn, "PathEdge::pathConnect(): attempted two connect "
"two vertices that disagree about the medium in between! "
"Please check your scene for leaks.");
#endif
++mediumInconsistencies;
result.release(pool);
return false;
}
medium = its.getTargetMedium(ray.d);
}
if (++interactions > 100) { /// Just a precaution..
SLog(EWarn, "pathConnect(): round-off error issues?");
result.release(pool);
return false;
}
}
if (medium != vs->getTargetMedium(predEdge, -d)) {
#if defined(MTS_BD_TRACE)
SLog(EWarn, "PathEdge::pathConnect(): attempted two connect "
"two vertices that disagree about the medium in between! "
"Please check your scene for leaks.");
#endif
++mediumInconsistencies;
result.release(pool);
return false;
}
}
result.reverse();
BDAssert(result.edgeCount() == result.vertexCount() + 1);
BDAssert((int) result.vertexCount() <= maxInteractions || maxInteractions < 0);
return true;
}
