C++ PathSampleGenerator类代码示例

bool MultiQuadLight::sampleDirect(uint32 threadIndex, const Vec3f &p, PathSampleGenerator &pathSampler, LightSample &sample) const
{
    float xi = pathSampler.next1D(EmitterSample);

    ThreadlocalSampleInfo &sampler = *_samplers[threadIndex];

    std::pair<int, float> result = _sampleBvh->sampleLight(p, &sampler.sampleWeights[0],
            &sampler.insideIds[0], xi, [&](uint32 id) {
        return approximateQuadContribution(p, id);
    });
    if (result.first == -1)
        return false;

    int idx = pathSampler.next1D(EmitterSample) < 0.5f ? result.first*2 : result.first*2 + 1;

    const QuadGeometry::TriangleInfo &t = _geometry.triangle(idx);

    Vec3f q = SampleWarp::uniformTriangle(pathSampler.next2D(EmitterSample), t.p0, t.p1, t.p2);
    Vec3f L = q - p;

    float rSq = L.lengthSq();
    sample.dist = std::sqrt(rSq);
    sample.d = L/sample.dist;
    float cosTheta = -(t.Ng.dot(sample.d));
    if (cosTheta <= 0.0f)
        return false;
    sample.pdf = result.second*0.5f*rSq/(cosTheta*_triangleAreas[idx]);

    return true;
}

bool Cube::samplePosition(PathSampleGenerator &sampler, PositionSample &sample) const
{
    float u = sampler.next1D();
    int dim = sampleFace(u);
    float s = (dim + 1) % 3;
    float t = (dim + 2) % 3;

    Vec2f xi = sampler.next2D();

    Vec3f n(0.0f);
    n[dim] = u < 0.5f ? -1.0f : 1.0f;

    Vec3f p(0.0f);
    p[dim] = n[dim]*_scale[dim];
    p[s] = (xi.x()*2.0f - 1.0f)*_scale[s];
    p[t] = (xi.y()*2.0f - 1.0f)*_scale[t];

    sample.p = _rot*p + _pos;
    sample.pdf = _invArea;
    sample.uv = xi;
    sample.weight = PI*_area*(*_emission)[sample.uv];
    sample.Ng = _rot*n;

    return true;
}

bool IsotropicPhaseFunction::sample(PathSampleGenerator &sampler, const Vec3f &/*wi*/, PhaseSample &sample) const
{
    sample.w = SampleWarp::uniformSphere(sampler.next2D());
    sample.weight = Vec3f(1.0f);
    sample.pdf = SampleWarp::uniformSpherePdf();
    return true;
}

bool Cube::sampleDirection(PathSampleGenerator &sampler, const PositionSample &point, DirectionSample &sample) const
{
    Vec3f d = SampleWarp::cosineHemisphere(sampler.next2D());
    sample.d = TangentFrame(point.Ng).toGlobal(d);
    sample.weight = Vec3f(1.0f);
    sample.pdf = SampleWarp::cosineHemispherePdf(d);

    return true;
}

bool Quad::sampleDirection(PathSampleGenerator &sampler, const PositionSample &/*point*/, DirectionSample &sample) const
{
    Vec3f d = SampleWarp::cosineHemisphere(sampler.next2D(EmitterSample));
    sample.d = _frame.toGlobal(d);
    sample.weight = Vec3f(1.0f);
    sample.pdf = SampleWarp::cosineHemispherePdf(d);

    return true;
}

float ErlangTransmittance::sampleSurface(PathSampleGenerator &sampler) const
{
    float xi = sampler.next1D();
    float x = 0.5f;
    for (int i = 0; i < 10; ++i) {
        x += (xi - (1.0f - surfaceSurface(Vec3f(x))[0]))/surfaceMedium(Vec3f(x))[0];
        x = max(x, 0.0f);
    }
    return x;
}

bool AtmosphericMedium::sampleDistance(PathSampleGenerator &sampler, const Ray &ray,
        MediumState &state, MediumSample &sample) const
{
    if (state.bounce > _maxBounce)
        return false;

    Vec3f p = (ray.pos() - _center);
    float t0 = p.dot(ray.dir());
    float  h = (p - t0*ray.dir()).length();

    float maxT = ray.farT() + t0;
    if (_absorptionOnly) {
        sample.t = ray.farT();
        sample.weight = std::exp(-_sigmaT*densityIntegral(h, t0, maxT));
        sample.pdf = 1.0f;
        sample.exited = true;
    } else {
        int component = sampler.nextDiscrete(3);
        float sigmaTc = _sigmaT[component];
        float xi = 1.0f - sampler.next1D();

        float t = inverseOpticalDepth(h, t0, sigmaTc, xi);
        sample.t = min(t, maxT);
        sample.weight = std::exp(-_sigmaT*densityIntegral(h, t0, sample.t));
        sample.exited = (t >= maxT);
        if (sample.exited) {
            sample.pdf = sample.weight.avg();
        } else {
            float rho = density(h, sample.t);
            sample.pdf = (rho*_sigmaT*sample.weight).avg();
            sample.weight *= rho*_sigmaS;
        }
        sample.weight /= sample.pdf;
        sample.t -= t0;

        state.advance();
    }
    sample.p = ray.pos() + sample.t*ray.dir();
    sample.phase = _phaseFunction.get();

    return true;
}

bool Quad::samplePosition(PathSampleGenerator &sampler, PositionSample &sample) const
{
    Vec2f xi = sampler.next2D(EmitterSample);
    sample.p = _base + xi.x()*_edge0 + xi.y()*_edge1;
    sample.pdf = _invArea;
    sample.uv = xi;
    sample.weight = PI*_area*(*_emission)[sample.uv];
    sample.Ng = _frame.normal;

    return true;
}

bool EquirectangularCamera::sampleDirection(PathSampleGenerator &sampler, const PositionSample &/*point*/, Vec2u pixel,
        DirectionSample &sample) const
{
    float pdf;
    Vec2f uv = (Vec2f(pixel) + 0.5f + _filter.sample(sampler.next2D(), pdf))*_pixelSize;

    float sinTheta;
    sample.d = uvToDirection(uv, sinTheta);
    sample.weight = Vec3f(1.0f);
    sample.pdf = INV_PI*INV_TWO_PI/sinTheta;

    return true;
}

bool HomogeneousMedium::sampleDistance(PathSampleGenerator &sampler, const Ray &ray,
        MediumState &state, MediumSample &sample) const
{
    if (state.bounce > _maxBounce)
        return false;

    float maxT = ray.farT();
    if (_absorptionOnly) {
        if (maxT == Ray::infinity())
            return false;
        sample.t = maxT;
        sample.weight = std::exp(-_sigmaT*maxT);
        sample.pdf = 1.0f;
        sample.exited = true;
    } else {
        int component = sampler.nextDiscrete(3);
        float sigmaTc = _sigmaT[component];

        float t = -std::log(1.0f - sampler.next1D())/sigmaTc;
        sample.t = min(t, maxT);
        sample.weight = std::exp(-sample.t*_sigmaT);
        sample.exited = (t >= maxT);
        if (sample.exited) {
            sample.pdf = sample.weight.avg();
        } else {
            sample.pdf = (_sigmaT*sample.weight).avg();
            sample.weight *= _sigmaS;
        }
        sample.weight /= sample.pdf;

        state.advance();
    }
    sample.p = ray.pos() + sample.t*ray.dir();
    sample.phase = _phaseFunction.get();

    return true;
}

bool Quad::sampleDirect(uint32 /*threadIndex*/, const Vec3f &p, PathSampleGenerator &sampler, LightSample &sample) const
{
    if (_frame.normal.dot(p - _base) <= 0.0f)
        return false;

    Vec2f xi = sampler.next2D(EmitterSample);
    Vec3f q = _base + xi.x()*_edge0 + xi.y()*_edge1;
    sample.d = q - p;
    float rSq = sample.d.lengthSq();
    sample.dist = std::sqrt(rSq);
    sample.d /= sample.dist;
    float cosTheta = -_frame.normal.dot(sample.d);
    sample.pdf = rSq/(cosTheta*_area);

    return true;
}

bool PinholeCamera::sampleDirection(PathSampleGenerator &sampler, const PositionSample &/*point*/, Vec2u pixel,
        DirectionSample &sample) const
{
    float pdf;
    Vec2f uv = _filter.sample(sampler.next2D(CameraSample), pdf);
    Vec3f localD = Vec3f(
        -1.0f  + (float(pixel.x()) + 0.5f + uv.x())*2.0f*_pixelSize.x(),
        _ratio - (float(pixel.y()) + 0.5f + uv.y())*2.0f*_pixelSize.x(),
        _planeDist
    ).normalized();

    sample.d =  _transform.transformVector(localD);
    sample.weight = Vec3f(1.0f);
    sample.pdf = _invPlaneArea/cube(localD.z());

    return true;
}

bool CubemapCamera::sampleDirection(PathSampleGenerator &sampler, const PositionSample &/*point*/, Vec2u pixel,
        DirectionSample &sample) const
{
    Vec2f uv = (Vec2f(pixel) + 0.5f)*_pixelSize;

    int face;
    if (!uvToFace(uv, face))
        return false;

    float filterPdf;
    uv += _filter.sample(sampler.next2D(CameraSample), filterPdf)*_pixelSize;

    sample.d = uvToDirection(face, uv, sample.pdf);
    sample.weight = Vec3f(1.0f);

    return true;
}

bool HenyeyGreensteinPhaseFunction::sample(PathSampleGenerator &sampler, const Vec3f &wi, PhaseSample &sample) const
{
    Vec2f xi = sampler.next2D(MediumPhaseSample);
    if (_g == 0.0f) {
        sample.w = SampleWarp::uniformSphere(xi);
        sample.weight = Vec3f(1.0f);
        sample.pdf = SampleWarp::uniformSpherePdf();
    } else {
        float phi = xi.x()*TWO_PI;
        float cosTheta = (1.0f + _g*_g - sqr((1.0f - _g*_g)/(1.0f + _g*(xi.y()*2.0f - 1.0f))))/(2.0f*_g);
        float sinTheta = std::sqrt(max(1.0f - cosTheta*cosTheta, 0.0f));
        sample.w = TangentFrame(wi).toGlobal(Vec3f(
            std::cos(phi)*sinTheta,
            std::sin(phi)*sinTheta,
            cosTheta
        ));
        sample.weight = Vec3f(1.0f);
        sample.pdf = henyeyGreenstein(cosTheta);
    }
    return true;
}

Vec3f PhotonTracer::traceSample(Vec2u pixel, const KdTree<Photon> &surfaceTree,
        const KdTree<VolumePhoton> *mediumTree, PathSampleGenerator &sampler,
        float gatherRadius)
{
    PositionSample point;
    if (!_scene->cam().samplePosition(sampler, point))
        return Vec3f(0.0f);
    DirectionSample direction;
    if (!_scene->cam().sampleDirection(sampler, point, pixel, direction))
        return Vec3f(0.0f);
    sampler.advancePath();

    Vec3f throughput = point.weight*direction.weight;
    Ray ray(point.p, direction.d);
    ray.setPrimaryRay(true);

    IntersectionTemporary data;
    IntersectionInfo info;
    const Medium *medium = _scene->cam().medium().get();

    Vec3f result(0.0f);
    int bounce = 0;
    bool didHit = _scene->intersect(ray, data, info);
    while ((medium || didHit) && bounce < _settings.maxBounces - 1) {
        if (medium) {
            if (mediumTree) {
                Vec3f beamEstimate(0.0f);
                mediumTree->beamQuery(ray.pos(), ray.dir(), ray.farT(), [&](const VolumePhoton &p, float t, float distSq) {
                    Ray mediumQuery(ray);
                    mediumQuery.setFarT(t);
                    beamEstimate += (3.0f*INV_PI*sqr(1.0f - distSq/p.radiusSq))/p.radiusSq
                            *medium->phaseFunction(p.pos)->eval(ray.dir(), -p.dir)
                            *medium->transmittance(mediumQuery)*p.power;
                });
                result += throughput*beamEstimate;
            }
            throughput *= medium->transmittance(ray);
        }
        if (!didHit)
            break;

        const Bsdf &bsdf = *info.bsdf;

        SurfaceScatterEvent event = makeLocalScatterEvent(data, info, ray, &sampler);

        Vec3f transparency = bsdf.eval(event.makeForwardEvent(), false);
        float transparencyScalar = transparency.avg();

        Vec3f wo;
        if (sampler.nextBoolean(DiscreteTransparencySample, transparencyScalar)) {
            wo = ray.dir();
            throughput *= transparency/transparencyScalar;
        } else {
            event.requestedLobe = BsdfLobes::SpecularLobe;
            if (!bsdf.sample(event, false))
                break;

            wo = event.frame.toGlobal(event.wo);

            throughput *= event.weight;
        }

        bool geometricBackside = (wo.dot(info.Ng) < 0.0f);
        medium = info.primitive->selectMedium(medium, geometricBackside);

        ray = ray.scatter(ray.hitpoint(), wo, info.epsilon);

        if (std::isnan(ray.dir().sum() + ray.pos().sum()))
            break;
        if (std::isnan(throughput.sum()))
            break;

        sampler.advancePath();
        bounce++;
        if (bounce < _settings.maxBounces)
            didHit = _scene->intersect(ray, data, info);
    }

    if (!didHit) {
        if (!medium && _scene->intersectInfinites(ray, data, info))
            result += throughput*info.primitive->evalDirect(data, info);
        return result;
    }
    if (info.primitive->isEmissive())
        result += throughput*info.primitive->evalDirect(data, info);

    int count = surfaceTree.nearestNeighbours(ray.hitpoint(), _photonQuery.get(), _distanceQuery.get(),
            _settings.gatherCount, gatherRadius);
    if (count == 0)
        return result;

    const Bsdf &bsdf = *info.bsdf;
    SurfaceScatterEvent event = makeLocalScatterEvent(data, info, ray, &sampler);

    Vec3f surfaceEstimate(0.0f);
    for (int i = 0; i < count; ++i) {
        event.wo = event.frame.toLocal(-_photonQuery[i]->dir);
        // Asymmetry due to shading normals already compensated for when storing the photon,
        // so we don't use the adjoint BSDF here
        surfaceEstimate += _photonQuery[i]->power*bsdf.eval(event, false)/std::abs(event.wo.z());
//.........这里部分代码省略.........