C++ MemoryArena类代码示例

void DipoleSubsurfaceIntegrator::Preprocess(const Scene *scene,
        const Camera *camera, const Renderer *renderer) {
    if (scene->lights.size() == 0) return;
    vector<SurfacePoint> pts;
    // Get _SurfacePoint_s for translucent objects in scene
    if (filename != "") {
        // Initialize _SurfacePoint_s from file
        vector<float> fpts;
        if (ReadFloatFile(filename.c_str(), &fpts)) {
            if ((fpts.size() % 8) != 0)
                Error("Excess values (%d) in points file \"%s\"", int(fpts.size() % 8),
                      filename.c_str());
            for (u_int i = 0; i < fpts.size(); i += 8)
                pts.push_back(SurfacePoint(Point(fpts[i], fpts[i+1], fpts[i+2]),
                                           Normal(fpts[i+3], fpts[i+4], fpts[i+5]),
                                           fpts[i+6], fpts[i+7]));
        }
    }
    if (pts.size() == 0) {
        Point pCamera = camera->CameraToWorld(camera->shutterOpen,
                                              Point(0, 0, 0));
        FindPoissonPointDistribution(pCamera, camera->shutterOpen,
                                     minSampleDist, scene, &pts);
    }

    // Compute irradiance values at sample points
    RNG rng;
    MemoryArena arena;
    PBRT_SUBSURFACE_STARTED_COMPUTING_IRRADIANCE_VALUES();
    ProgressReporter progress(pts.size(), "Computing Irradiances");
    for (uint32_t i = 0; i < pts.size(); ++i) {
        SurfacePoint &sp = pts[i];
        Spectrum E(0.f);
        for (uint32_t j = 0; j < scene->lights.size(); ++j) {
            // Add irradiance from light at point
            const Light *light = scene->lights[j];
            Spectrum Elight = 0.f;
            int nSamples = RoundUpPow2(light->nSamples);
            uint32_t scramble[2] = { rng.RandomUInt(), rng.RandomUInt() };
            uint32_t compScramble = rng.RandomUInt();
            for (int s = 0; s < nSamples; ++s) {
                float lpos[2];
                Sample02(s, scramble, lpos);
                float lcomp = VanDerCorput(s, compScramble);
                LightSample ls(lpos[0], lpos[1], lcomp);
                Vector wi;
                float lightPdf;
                VisibilityTester visibility;
                Spectrum Li = light->Sample_L(sp.p, sp.rayEpsilon,
                    ls, camera->shutterOpen, &wi, &lightPdf, &visibility);
                if (Dot(wi, sp.n) <= 0.) continue;
                if (Li.IsBlack() || lightPdf == 0.f) continue;
                Li *= visibility.Transmittance(scene, renderer, NULL, rng, arena);
                if (visibility.Unoccluded(scene))
                    Elight += Li * AbsDot(wi, sp.n) / lightPdf;
            }
            E += Elight / nSamples;
        }
        irradiancePoints.push_back(IrradiancePoint(sp, E));
        PBRT_SUBSURFACE_COMPUTED_IRRADIANCE_AT_POINT(&sp, &E);
        arena.FreeAll();
        progress.Update();
    }
    progress.Done();
    PBRT_SUBSURFACE_FINISHED_COMPUTING_IRRADIANCE_VALUES();

    // Create octree of clustered irradiance samples
    octree = octreeArena.Alloc<SubsurfaceOctreeNode>();
    for (uint32_t i = 0; i < irradiancePoints.size(); ++i)
        octreeBounds = Union(octreeBounds, irradiancePoints[i].p);
    for (uint32_t i = 0; i < irradiancePoints.size(); ++i)
        octree->Insert(octreeBounds, &irradiancePoints[i], octreeArena);
    octree->InitHierarchy();
}

void IGIIntegrator::Preprocess(const Scene *scene, const Camera *camera,
                               const Renderer *renderer) {
    if (scene->lights.size() == 0) return;
    MemoryArena arena;
    RNG rng;
    // Compute samples for emitted rays from lights
    vector<float> lightNum(nLightPaths * nLightSets);
    vector<float> lightSampPos(2 * nLightPaths * nLightSets, 0.f);
    vector<float> lightSampComp(nLightPaths * nLightSets, 0.f);
    vector<float> lightSampDir(2 * nLightPaths * nLightSets, 0.f);
    LDShuffleScrambled1D(nLightPaths, nLightSets, &lightNum[0], rng);
    LDShuffleScrambled2D(nLightPaths, nLightSets, &lightSampPos[0], rng);
    LDShuffleScrambled1D(nLightPaths, nLightSets, &lightSampComp[0], rng);
    LDShuffleScrambled2D(nLightPaths, nLightSets, &lightSampDir[0], rng);

    // Precompute information for light sampling densities
    Distribution1D *lightDistribution = ComputeLightSamplingCDF(scene);
    for (uint32_t s = 0; s < nLightSets; ++s) {
        for (uint32_t i = 0; i < nLightPaths; ++i) {
            // Follow path _i_ from light to create virtual lights
            int sampOffset = s*nLightPaths + i;

            // Choose light source to trace virtual light path from
            float lightPdf;
            int ln = lightDistribution->SampleDiscrete(lightNum[sampOffset],
                                                       &lightPdf);
            Light *light = scene->lights[ln];

            // Sample ray leaving light source for virtual light path
            RayDifferential ray;
            float pdf;
            LightSample ls(lightSampPos[2*sampOffset], lightSampPos[2*sampOffset+1],
                           lightSampComp[sampOffset]);
            Normal Nl;
            Spectrum alpha = light->Sample_L(scene, ls, lightSampDir[2*sampOffset],
                                             lightSampDir[2*sampOffset+1],
                                             camera->shutterOpen, &ray, &Nl, &pdf);
            if (pdf == 0.f || alpha.IsBlack()) continue;
            alpha *= AbsDot(Nl, ray.d) / (pdf * lightPdf);
            Intersection isect;
            while (scene->Intersect(ray, &isect) && !alpha.IsBlack()) {
                // Create virtual light and sample new ray for path
                alpha *= renderer->Transmittance(scene, RayDifferential(ray), NULL,
                                                 rng, arena);
                Vector wo = -ray.d;
                BSDF *bsdf = isect.GetBSDF(ray, arena);

                // Create virtual light at ray intersection point
                Spectrum contrib = alpha * bsdf->rho(wo, rng) / M_PI;
                virtualLights[s].push_back(VirtualLight(isect.dg.p, isect.dg.nn, contrib,
                                                        isect.rayEpsilon));

                // Sample new ray direction and update weight for virtual light path
                Vector wi;
                float pdf;
                BSDFSample bsdfSample(rng);
                Spectrum fr = bsdf->Sample_f(wo, &wi, bsdfSample, &pdf);
                if (fr.IsBlack() || pdf == 0.f)
                    break;
                Spectrum contribScale = fr * AbsDot(wi, bsdf->dgShading.nn) / pdf;

                // Possibly terminate virtual light path with Russian roulette
                float rrProb = min(1.f, contribScale.y());
                if (rng.RandomFloat() > rrProb)
                    break;
                alpha *= contribScale / rrProb;
                ray = RayDifferential(isect.dg.p, wi, ray, isect.rayEpsilon);
            }
            arena.FreeAll();
        }
    }
    delete lightDistribution;
}

void BDPTIntegrator::Render(const Scene &scene) {
    ProfilePhase p(Prof::IntegratorRender);
    // Compute _lightDistr_ for sampling lights proportional to power
    std::unique_ptr<Distribution1D> lightDistr =
        ComputeLightPowerDistribution(scene);

    // Partition the image into tiles
    Film *film = camera->film;
    const Bounds2i sampleBounds = film->GetSampleBounds();
    const Vector2i sampleExtent = sampleBounds.Diagonal();
    const int tileSize = 16;
    const int nXTiles = (sampleExtent.x + tileSize - 1) / tileSize;
    const int nYTiles = (sampleExtent.y + tileSize - 1) / tileSize;
    ProgressReporter reporter(nXTiles * nYTiles, "Rendering");

    // Allocate buffers for debug visualization
    const int bufferCount = (1 + maxDepth) * (6 + maxDepth) / 2;
    std::vector<std::unique_ptr<Film>> weightFilms(bufferCount);
    if (visualizeStrategies || visualizeWeights) {
        for (int depth = 0; depth <= maxDepth; ++depth) {
            for (int s = 0; s <= depth + 2; ++s) {
                int t = depth + 2 - s;
                if (t == 0 || (s == 1 && t == 1)) continue;

                char filename[32];
                snprintf(filename, sizeof(filename),
                         "bdpt_d%02i_s%02i_t%02i.exr", depth, s, t);

                weightFilms[BufferIndex(s, t)] = std::unique_ptr<Film>(new Film(
                    film->fullResolution,
                    Bounds2f(Point2f(0, 0), Point2f(1, 1)),
                    std::unique_ptr<Filter>(CreateBoxFilter(ParamSet())),
                    film->diagonal * 1000, filename, 1.f));
            }
        }
    }

    // Render and write the output image to disk
    if (scene.lights.size() > 0) {
        StatTimer timer(&renderingTime);
        ParallelFor([&](const Point2i tile) {
            // Render a single tile using BDPT
            MemoryArena arena;
            int seed = tile.y * nXTiles + tile.x;
            std::unique_ptr<Sampler> tileSampler = sampler->Clone(seed);
            int x0 = sampleBounds.pMin.x + tile.x * tileSize;
            int x1 = std::min(x0 + tileSize, sampleBounds.pMax.x);
            int y0 = sampleBounds.pMin.y + tile.y * tileSize;
            int y1 = std::min(y0 + tileSize, sampleBounds.pMax.y);
            Bounds2i tileBounds(Point2i(x0, y0), Point2i(x1, y1));
            std::unique_ptr<FilmTile> filmTile =
                camera->film->GetFilmTile(tileBounds);
            for (Point2i pPixel : tileBounds) {
                tileSampler->StartPixel(pPixel);
                do {
                    // Generate a single sample using BDPT
                    Point2f pFilm = (Point2f)pPixel + tileSampler->Get2D();

                    // Trace the camera and light subpaths
                    Vertex *cameraVertices = arena.Alloc<Vertex>(maxDepth + 2);
                    Vertex *lightVertices = arena.Alloc<Vertex>(maxDepth + 1);
                    int nCamera = GenerateCameraSubpath(
                        scene, *tileSampler, arena, maxDepth + 2, *camera,
                        pFilm, cameraVertices);
                    int nLight = GenerateLightSubpath(
                        scene, *tileSampler, arena, maxDepth + 1,
                        cameraVertices[0].time(), *lightDistr, lightVertices);

                    // Execute all BDPT connection strategies
                    Spectrum L(0.f);
                    for (int t = 1; t <= nCamera; ++t) {
                        for (int s = 0; s <= nLight; ++s) {
                            int depth = t + s - 2;
                            if ((s == 1 && t == 1) || depth < 0 ||
                                depth > maxDepth)
                                continue;
                            // Execute the $(s, t)$ connection strategy and
                            // update _L_
                            Point2f pFilmNew = pFilm;
                            Float misWeight = 0.f;
                            Spectrum Lpath = ConnectBDPT(
                                scene, lightVertices, cameraVertices, s, t,
                                *lightDistr, *camera, *tileSampler, &pFilmNew,
                                &misWeight);
                            if (visualizeStrategies || visualizeWeights) {
                                Spectrum value;
                                if (visualizeStrategies)
                                    value =
                                        misWeight == 0 ? 0 : Lpath / misWeight;
                                if (visualizeWeights) value = Lpath;
                                weightFilms[BufferIndex(s, t)]->AddSplat(
                                    pFilmNew, value);
                            }
                            if (t != 1)
                                L += Lpath;
                            else
                                film->AddSplat(pFilmNew, Lpath);
                        }
                    }
                    filmTile->AddSample(pFilm, L);
//.........这里部分代码省略.........

void PhotonShootingTask::Run() {
    // Declare local variables for _PhotonShootingTask_
    MemoryArena arena;
    RNG rng(31 * taskNum);
    vector<Photon> localDirectPhotons, localIndirectPhotons, localCausticPhotons;
    vector<RadiancePhoton> localRadiancePhotons;
    u_int 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 u_int blockSize = 4096;
        for (u_int 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],
                                          &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;
                u_int nIntersections = 0;
                while (scene->Intersect(photonRay, &photonIsect)) {
                    ++nIntersections;
                    // Handle photon/surface intersection
                    alpha *= renderer->Transmittance(scene, photonRay, NULL, arena, &rng);
                    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 (nIntersections == 1) {
                            PBRT_PHOTON_MAP_DEPOSITED_DIRECT_PHOTON(&photonIsect.dg, &alpha, &wo);
                            depositedPhoton = true;
                            localDirectPhotons.push_back(photon);
                        }
                        else {
                            // Deposit either caustic or indirect photon
                            if (specularPath && !causticDone) {
                                PBRT_PHOTON_MAP_DEPOSITED_CAUSTIC_PHOTON(&photonIsect.dg, &alpha, &wo);
                                depositedPhoton = true;
                                localCausticPhotons.push_back(photon);
                            }
                            else if (!specularPath && !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) {
                            // Store data for radiance photon
                            Normal n = photonIsect.dg.nn;
                            n = Faceforward(n, -photonRay.d);
                            localRadiancePhotons.push_back(RadiancePhoton(photonIsect.dg.p, n));

                            // Generate random samples for computing reflectance and transmittance
                            const int sqrtRhoSamples = 4;
                            float rhoRSamples1[2*sqrtRhoSamples*sqrtRhoSamples];
                            float rhoRSamples2[2*sqrtRhoSamples*sqrtRhoSamples];
                            StratifiedSample2D(rhoRSamples1, sqrtRhoSamples, sqrtRhoSamples, rng);
                            StratifiedSample2D(rhoRSamples2, sqrtRhoSamples, sqrtRhoSamples, rng);
                            float rhoTSamples1[2*sqrtRhoSamples*sqrtRhoSamples];
                            float rhoTSamples2[2*sqrtRhoSamples*sqrtRhoSamples];
                            StratifiedSample2D(rhoTSamples1, sqrtRhoSamples, sqrtRhoSamples, rng);
                            StratifiedSample2D(rhoTSamples2, sqrtRhoSamples, sqrtRhoSamples, rng);
                            Spectrum rho_r = photonBSDF->rho(sqrtRhoSamples * sqrtRhoSamples,
                                rhoRSamples1, rhoRSamples2, BSDF_ALL_REFLECTION);
                            localRpReflectances.push_back(rho_r);
                            Spectrum rho_t = photonBSDF->rho(sqrtRhoSamples * sqrtRhoSamples,
                                rhoTSamples1, rhoTSamples2, BSDF_ALL_TRANSMISSION);
                            localRpTransmittances.push_back(rho_t);
                        }
                    }
                    if ((int)nIntersections >= integrator->maxPhotonDepth) break;

                    // Sample new photon ray direction
                    Vector wi;
//.........这里部分代码省略.........

void BDPTIntegrator::Render(const Scene &scene) {
    // Compute _lightDistr_ for sampling lights proportional to power
    std::unique_ptr<Distribution1D> lightDistr(ComputeLightSamplingCDF(scene));

    // Partition the image into buckets
    Film *film = camera->film;
    const Bounds2i sampleBounds = film->GetSampleBounds();
    const Vector2i sampleExtent = sampleBounds.Diagonal();
    const int bucketSize = 16;
    const int nXBuckets = (sampleExtent.x + bucketSize - 1) / bucketSize;
    const int nYBuckets = (sampleExtent.y + bucketSize - 1) / bucketSize;
    ProgressReporter reporter(nXBuckets * nYBuckets, "Rendering");

    // Allocate buffers for debug visualization
    const int bufferCount = (1 + maxdepth) * (6 + maxdepth) / 2;
    std::vector<std::unique_ptr<Film>> films(bufferCount);
    if (visualize_strategies || visualize_weights) {
        for (int depth = 0; depth <= maxdepth; ++depth) {
            for (int s = 0; s <= depth + 2; ++s) {
                int t = depth + 2 - s;
                if (t == 0 || (s == 1 && t == 1)) continue;

                char filename[32];
                snprintf(filename, sizeof(filename),
                         "bdpt_d%02i_s%02i_t%02i.exr", depth, s, t);

                films[BufferIndex(s, t)] = std::unique_ptr<Film>(new Film(
                    film->fullResolution,
                    Bounds2f(Point2f(0, 0), Point2f(1, 1)),
                    CreateBoxFilter(ParamSet()),
                    film->diagonal * 1000,  // XXX what does this parameter
                                            // mean? Why the multiplication?
                    filename, 1.f, 2.2f));
            }
        }
    }

    // Render and write the output image to disk
    {
        StatTimer timer(&renderingTime);
        ParallelFor([&](const Point2i bucket) {
            // Render a single bucket using BDPT
            MemoryArena arena;
            int seed = bucket.y * nXBuckets + bucket.x;
            std::unique_ptr<Sampler> bucketSampler = sampler->Clone(seed);
            int x0 = sampleBounds.pMin.x + bucket.x * bucketSize;
            int x1 = std::min(x0 + bucketSize, sampleBounds.pMax.x);
            int y0 = sampleBounds.pMin.y + bucket.y * bucketSize;
            int y1 = std::min(y0 + bucketSize, sampleBounds.pMax.y);
            Bounds2i bucketBounds(Point2i(x0, y0), Point2i(x1, y1));
            std::unique_ptr<FilmTile> filmTile =
                camera->film->GetFilmTile(bucketBounds);
            for (Point2i pixel : bucketBounds) {
                bucketSampler->StartPixel(pixel);
                do {
                    // Generate a single sample using BDPT
                    Point2f rasterPos((Float)pixel.x, (Float)pixel.y);
                    rasterPos += bucketSampler->Get2D();

                    // Trace the light and camera subpaths
                    Vertex *cameraSubpath =
                        (Vertex *)arena.Alloc<Vertex>(maxdepth + 2);
                    Vertex *lightSubpath =
                        (Vertex *)arena.Alloc<Vertex>(maxdepth + 1);
                    int nCamera = GenerateCameraSubpath(
                        scene, *bucketSampler, arena, maxdepth + 2, *camera,
                        rasterPos, cameraSubpath);
                    int nLight = GenerateLightSubpath(
                        scene, *bucketSampler, arena, maxdepth + 1,
                        cameraSubpath[0].GetTime(), *lightDistr, lightSubpath);

                    // Execute all connection strategies
                    Spectrum pixelWeight(0.f);
                    for (int t = 1; t <= nCamera; ++t) {
                        for (int s = 0; s <= nLight; ++s) {
                            int depth = t + s - 2;
                            if ((s == 1 && t == 1) || depth < 0 ||
                                depth > maxdepth)
                                continue;
                            // Execute the $(s, t)$ connection strategy
                            Point2f finalRasterPos = rasterPos;
                            Float misWeight = 0.f;
                            Spectrum weight = ConnectBDPT(
                                scene, lightSubpath, cameraSubpath, s, t,
                                *lightDistr, *camera, *bucketSampler,
                                &finalRasterPos, &misWeight);
                            if (visualize_strategies || visualize_weights) {
                                Spectrum value(1.0f);
                                if (visualize_strategies) value *= weight;
                                if (visualize_weights) value *= misWeight;
                                films[BufferIndex(s, t)]->Splat(finalRasterPos,
                                                                value);
                            }
                            if (t != 1)
                                pixelWeight += weight * misWeight;
                            else
                                film->Splat(finalRasterPos, weight * misWeight);
                        }
                    }
                    filmTile->AddSample(rasterPos, pixelWeight, 1.0f);
//.........这里部分代码省略.........

void LightShootingTask::Run() {
    // tady by mel byt kod z photon mappingu

    MemoryArena arena;
    uint32_t totalPaths = 0;
    RNG rng(seed);
    PermutedHalton halton(6, rng);
    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;
                    //MC tady by mel byt i kod pro volumetriku

                    // Handle photon/surface intersection
                    // alpha *= renderer->Transmittance(scene, photonRay, NULL, rng, arena);
                    BSDF *photonBSDF = photonIsect.GetBSDF(photonRay, arena);

                    Vector wo = -photonRay.d;
                    //MC tady se ukladaly photony takze tady bych mel ukladat samples do filmu kamery
                    //  // Deposit photon at surface
                    //Photon photon(photonIsect.dg.p, alpha, wo);
                    //tuhle metodu chci pouzit
                    //filmAddSample()

                    if (nIntersections >= maxDepth) 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);

                    photonRay = RayDifferential(photonIsect.dg.p, wi, photonRay,
                                                photonIsect.rayEpsilon);

                }
                PBRT_PHOTON_MAP_FINISHED_RAY_PATH(&photonRay, &alpha);
            }

            arena.FreeAll();
        }

        //termination criteria ???
        if (totalPaths==maxPathCount) {
            break;
        }
    }
}