C++ VisibilityTester::Tr方法代码示例

Spectrum EstimateDirect(const Interaction &it, const Point2f &uScattering,
                        const Light &light, const Point2f &uLight,
                        const Scene &scene, Sampler &sampler,
                        MemoryArena &arena, bool handleMedia, bool specular) {
    BxDFType bsdfFlags =
        specular ? BSDF_ALL : BxDFType(BSDF_ALL & ~BSDF_SPECULAR);
    Spectrum Ld(0.f);
    // Sample light source with multiple importance sampling
    Vector3f wi;
    Float lightPdf = 0, scatteringPdf = 0;
    VisibilityTester visibility;
    Spectrum Li = light.Sample_Li(it, uLight, &wi, &lightPdf, &visibility);
    if (lightPdf > 0 && !Li.IsBlack()) {
        // Compute BSDF or phase function's value for light sample
        Spectrum f;
        if (it.IsSurfaceInteraction()) {
            // Evaluate BSDF for light sampling strategy
            const SurfaceInteraction &isect = (const SurfaceInteraction &)it;
            f = isect.bsdf->f(isect.wo, wi, bsdfFlags) *
                AbsDot(wi, isect.shading.n);
            scatteringPdf = isect.bsdf->Pdf(isect.wo, wi, bsdfFlags);
        } else {
            // Evaluate phase function for light sampling strategy
            const MediumInteraction &mi = (const MediumInteraction &)it;
            Float p = mi.phase->p(mi.wo, wi);
            f = Spectrum(p);
            scatteringPdf = p;
        }
        if (!f.IsBlack()) {
            // Compute effect of visibility for light source sample
            if (handleMedia)
                Li *= visibility.Tr(scene, sampler);
            else if (!visibility.Unoccluded(scene))
                Li = Spectrum(0.f);

            // Add light's contribution to reflected radiance
            if (!Li.IsBlack()) {
                if (IsDeltaLight(light.flags))
                    Ld += f * Li / lightPdf;
                else {
                    Float weight =
                        PowerHeuristic(1, lightPdf, 1, scatteringPdf);
                    Ld += f * Li * weight / lightPdf;
                }
            }
        }
    }

    // Sample BSDF with multiple importance sampling
    if (!IsDeltaLight(light.flags)) {
        Spectrum f;
        bool sampledSpecular = false;
        if (it.IsSurfaceInteraction()) {
            // Sample scattered direction for surface interactions
            BxDFType sampledType;
            const SurfaceInteraction &isect = (const SurfaceInteraction &)it;
            f = isect.bsdf->Sample_f(isect.wo, &wi, uScattering, &scatteringPdf,
                                     bsdfFlags, &sampledType);
            f *= AbsDot(wi, isect.shading.n);
            sampledSpecular = sampledType & BSDF_SPECULAR;
        } else {
            // Sample scattered direction for medium interactions
            const MediumInteraction &mi = (const MediumInteraction &)it;
            Float p = mi.phase->Sample_p(mi.wo, &wi, uScattering);
            f = Spectrum(p);
            scatteringPdf = p;
        }
        if (!f.IsBlack() && scatteringPdf > 0) {
            // Account for light contributions along sampled direction _wi_
            Float weight = 1;
            if (!sampledSpecular) {
                lightPdf = light.Pdf_Li(it, wi);
                if (lightPdf == 0) return Ld;
                weight = PowerHeuristic(1, scatteringPdf, 1, lightPdf);
            }

            // Find intersection and compute transmittance
            SurfaceInteraction lightIsect;
            Ray ray = it.SpawnRay(wi);
            Spectrum Tr(1.f);
            bool foundSurfaceInteraction =
                handleMedia ? scene.IntersectTr(ray, sampler, &lightIsect, &Tr)
                            : scene.Intersect(ray, &lightIsect);

            // Add light contribution from material sampling
            Spectrum Li(0.f);
            if (foundSurfaceInteraction) {
                if (lightIsect.primitive->GetAreaLight() == &light)
                    Li = lightIsect.Le(-wi);
            } else
                Li = light.Le(ray);
            if (!Li.IsBlack()) Ld += f * Li * Tr * weight / scatteringPdf;
        }
    }
    return Ld;
}

Spectrum ConnectBDPT(
    const Scene &scene, Vertex *lightVertices, Vertex *cameraVertices, int s,
    int t, const Distribution1D &lightDistr,
    const std::unordered_map<const Light *, size_t> &lightToIndex,
    const Camera &camera, Sampler &sampler, Point2f *pRaster,
    Float *misWeightPtr) {
    Spectrum L(0.f);
    // Ignore invalid connections related to infinite area lights
    if (t > 1 && s != 0 && cameraVertices[t - 1].type == VertexType::Light)
        return Spectrum(0.f);

    // Perform connection and write contribution to _L_
    Vertex sampled;
    if (s == 0) {
        // Interpret the camera subpath as a complete path
        const Vertex &pt = cameraVertices[t - 1];
        if (pt.IsLight()) L = pt.Le(scene, cameraVertices[t - 2]) * pt.beta;
        DCHECK(!L.HasNaNs());
    } else if (t == 1) {
        // Sample a point on the camera and connect it to the light subpath
        const Vertex &qs = lightVertices[s - 1];
        if (qs.IsConnectible()) {
            VisibilityTester vis;
            Vector3f wi;
            Float pdf;
            Spectrum Wi = camera.Sample_Wi(qs.GetInteraction(), sampler.Get2D(),
                                           &wi, &pdf, pRaster, &vis);
            if (pdf > 0 && !Wi.IsBlack()) {
                // Initialize dynamically sampled vertex and _L_ for $t=1$ case
                sampled = Vertex::CreateCamera(&camera, vis.P1(), Wi / pdf);
                L = qs.beta * qs.f(sampled, TransportMode::Importance) * sampled.beta;
                if (qs.IsOnSurface()) L *= AbsDot(wi, qs.ns());
                DCHECK(!L.HasNaNs());
                // Only check visibility after we know that the path would
                // make a non-zero contribution.
                if (!L.IsBlack()) L *= vis.Tr(scene, sampler);
            }
        }
    } else if (s == 1) {
        // Sample a point on a light and connect it to the camera subpath
        const Vertex &pt = cameraVertices[t - 1];
        if (pt.IsConnectible()) {
            Float lightPdf;
            VisibilityTester vis;
            Vector3f wi;
            Float pdf;
            int lightNum =
                lightDistr.SampleDiscrete(sampler.Get1D(), &lightPdf);
            const std::shared_ptr<Light> &light = scene.lights[lightNum];
            Spectrum lightWeight = light->Sample_Li(
                pt.GetInteraction(), sampler.Get2D(), &wi, &pdf, &vis);
            if (pdf > 0 && !lightWeight.IsBlack()) {
                EndpointInteraction ei(vis.P1(), light.get());
                sampled =
                    Vertex::CreateLight(ei, lightWeight / (pdf * lightPdf), 0);
                sampled.pdfFwd =
                    sampled.PdfLightOrigin(scene, pt, lightDistr, lightToIndex);
                L = pt.beta * pt.f(sampled, TransportMode::Radiance) * sampled.beta;
                if (pt.IsOnSurface()) L *= AbsDot(wi, pt.ns());
                // Only check visibility if the path would carry radiance.
                if (!L.IsBlack()) L *= vis.Tr(scene, sampler);
            }
        }
    } else {
        // Handle all other bidirectional connection cases
        const Vertex &qs = lightVertices[s - 1], &pt = cameraVertices[t - 1];
        if (qs.IsConnectible() && pt.IsConnectible()) {
            L = qs.beta * qs.f(pt, TransportMode::Importance) * pt.f(qs, TransportMode::Radiance) * pt.beta;
            VLOG(2) << "General connect s: " << s << ", t: " << t <<
                " qs: " << qs << ", pt: " << pt << ", qs.f(pt): " << qs.f(pt, TransportMode::Importance) <<
                ", pt.f(qs): " << pt.f(qs, TransportMode::Radiance) << ", G: " << G(scene, sampler, qs, pt) <<
                ", dist^2: " << DistanceSquared(qs.p(), pt.p());
            if (!L.IsBlack()) L *= G(scene, sampler, qs, pt);
        }
    }

    ++totalPaths;
    if (L.IsBlack()) ++zeroRadiancePaths;
    ReportValue(pathLength, s + t - 2);

    // Compute MIS weight for connection strategy
    Float misWeight =
        L.IsBlack() ? 0.f : MISWeight(scene, lightVertices, cameraVertices,
                                      sampled, s, t, lightDistr, lightToIndex);
    VLOG(2) << "MIS weight for (s,t) = (" << s << ", " << t << ") connection: "
            << misWeight;
    DCHECK(!std::isnan(misWeight));
    L *= misWeight;
    if (misWeightPtr) *misWeightPtr = misWeight;
    return L;
}

Spectrum ConnectBDPT(const Scene &scene, Vertex *lightVertices,
                     Vertex *cameraVertices, int s, int t,
                     const Distribution1D &lightDistr, const Camera &camera,
                     Sampler &sampler, Point2f *pRaster, Float *misWeightPtr) {
    Spectrum L(0.f);
    // Ignore invalid connections related to infinite area lights
    if (t > 1 && s != 0 && cameraVertices[t - 1].type == VertexType::Light)
        return Spectrum(0.f);

    // Perform connection and write contribution to _L_
    Vertex sampled;
    if (s == 0) {
        // Interpret the camera subpath as a complete path
        const Vertex &pt = cameraVertices[t - 1];
        if (pt.IsLight()) L = pt.Le(scene, cameraVertices[t - 2]) * pt.beta;
    } else if (t == 1) {
        // Sample a point on the camera and connect it to the light subpath
        const Vertex &qs = lightVertices[s - 1];
        if (qs.IsConnectible()) {
            VisibilityTester vis;
            Vector3f wi;
            Float pdf;
            Spectrum Wi = camera.Sample_Wi(qs.GetInteraction(), sampler.Get2D(),
                                           &wi, &pdf, pRaster, &vis);
            if (pdf > 0 && !Wi.IsBlack()) {
                // Initialize dynamically sampled vertex and _L_ for $t=1$ case
                sampled = Vertex::CreateCamera(&camera, vis.P1(), Wi / pdf);
                L = qs.beta * qs.f(sampled) * vis.Tr(scene, sampler) *
                    sampled.beta;
                if (qs.IsOnSurface()) L *= AbsDot(wi, qs.ns());
            }
        }
    } else if (s == 1) {
        // Sample a point on a light and connect it to the camera subpath
        const Vertex &pt = cameraVertices[t - 1];
        if (pt.IsConnectible()) {
            Float lightPdf;
            VisibilityTester vis;
            Vector3f wi;
            Float pdf;
            int lightNum =
                lightDistr.SampleDiscrete(sampler.Get1D(), &lightPdf);
            const std::shared_ptr<Light> &light = scene.lights[lightNum];
            Spectrum lightWeight = light->Sample_Li(
                pt.GetInteraction(), sampler.Get2D(), &wi, &pdf, &vis);
            if (pdf > 0 && !lightWeight.IsBlack()) {
                EndpointInteraction ei(vis.P1(), light.get());
                sampled =
                    Vertex::CreateLight(ei, lightWeight / (pdf * lightPdf), 0);
                sampled.pdfFwd = sampled.PdfLightOrigin(scene, pt, lightDistr);
                L = pt.beta * pt.f(sampled) * vis.Tr(scene, sampler) *
                    sampled.beta;
                if (pt.IsOnSurface()) L *= AbsDot(wi, pt.ns());
            }
        }
    } else {
        // Handle all other bidirectional connection cases
        const Vertex &qs = lightVertices[s - 1], &pt = cameraVertices[t - 1];
        if (qs.IsConnectible() && pt.IsConnectible()) {
            L = qs.beta * qs.f(pt) * pt.f(qs) * pt.beta;
            if (!L.IsBlack()) L *= G(scene, sampler, qs, pt);
        }
    }

    // Compute MIS weight for connection strategy
    Float misWeight =
        L.IsBlack() ? 0.f : MISWeight(scene, lightVertices, cameraVertices,
                                      sampled, s, t, lightDistr);
    L *= misWeight;
    if (misWeightPtr) *misWeightPtr = misWeight;
    return L;
}