Beispiel #1
0
void VolumePatIntegrator::EyeRandomWalk(const Scene *scene, const Ray &eyeRay,
        VolumeVertexList& vertexList, RNG &rng) const {
    // Do a random walk for the eye ray in the volume
    Spectrum cummulative(1.f);

    // Find the intersection between the eye ray and the volume
    VolumeRegion *vr = scene->volumeRegion;
    float t0, t1;
    if (!vr || !vr->IntersectP(eyeRay, &t0, &t1) || (t1-t0) == 0.f || t0 < 0.f) {
        return;
    }

    // Find the intersection point between the sampled light ray and the volume
    RayDifferential ray(eyeRay);
    Point p = ray(t0), pPrev;
    uint64_t bounces = 0;
    while(vr->WorldBound().Inside(p)) {
        Vector wi = -ray.d;
        const Spectrum sigma_a = vr->Sigma_a(p, wi, eyeRay.time);
        const Spectrum sigma_s = vr->Sigma_s(p, wi, eyeRay.time);
        const Spectrum STER = vr->STER(p, wi, eyeRay.time);
        // Construct and add the _eyeVertex_ to the _vertexList_
        VolumeVertex eyeVertex(p, wi, sigma_a, sigma_s, cummulative, 1.0);
        vertexList.push_back(eyeVertex);

        // Sample the direction of the next event
        float directionPdf = 1.f;
        Vector wo;
        if(STER.y() > rng.RandomFloat()) {
            // Change the ray direction due to a scattering event at _p_
            if(!vr->SampleDirection(p, wi, wo, &directionPdf, rng)) {
                break; // Direction error
            }

            // Account for the losses due to the scattering event at _p_
            cummulative *= sigma_s * vr->p(p, wi, wo, ray.time);
        } else {
            // Account only for the trnsmittance between the previous and the
            // next events becuse there is no direction change.
            wo = ray.d;
        }

        // Sample the distance of the next event
        ray = RayDifferential(p, wo, 0, INFINITY);

        float tDist;
        float distancePdf = 1.f;
        Point Psample;
        if(!vr->SampleDistance(ray, &tDist, Psample, &distancePdf, rng)) {
            break; // The sampled point is outside the volume
        }

        // Account for the sampling Pdfs from sampling a direction and/or distance
        const float pdf = distancePdf * directionPdf;
        cummulative *= 1 / pdf;

        // Update the events and account for the transmittance between the events
        pPrev = p;
        p = Psample;
        const Ray tauRay(pPrev, p - pPrev, 0.f, 1.f, ray.time, ray.depth);
        const Spectrum stepTau = vr->tau(tauRay, .5f * stepSize, rng.RandomFloat());
        const Spectrum TrPP = Exp(-stepTau);
        cummulative *= TrPP;

        // Possibly terminate ray marching if _cummulative_ is small
        if (cummulative.y() < 1e-3) {
            const float continueProb = .5f;
            if (rng.RandomFloat() > continueProb) {
                cummulative = 0.f;
                break;
            }
            cummulative /= continueProb;
        }

        // Terminate if bounces are more than requested
        bounces++;
        if (bounces > maxDepth) {
            break;
        }
    }
}
Beispiel #2
0
Spectrum VSDScatteringIntegrator::LiMultiple(const Scene *scene, const Renderer *renderer,
        const RayDifferential &ray, const Sample *sample, RNG &rng,
        Spectrum *T, MemoryArena &arena) const {
    VolumeRegion *vr = scene->volumeRegion;
    float t0, t1;
    vr->IntersectP(ray, &t0, &t1);

    // Do multiple scattering volume integration in _vr_
    Spectrum Lv(0.);

    // Prepare for random walk
    Spectrum Tr(1.f);

    Point p = ray(t0), pPrev = ray.o;

    // printf("%f %f %f, ", p.x, p.y, p.z);

    int steps = 0;
    // Sample the events in a random walk

//    BBox bb = vr->WorldBound();
//    printf("%f %f %f & %f %f %f \n",
//           bb.pMin.x, bb.pMin.y, bb.pMin.z, bb.pMax.x, bb.pMax.y, bb.pMax.z);


    while(vr->WorldBound().Inside(p)) {
        //printf("%f %f %f %d \n", p.x, p.y, p.z, steps);
        steps++;
        // Sample direction
        Vector wi = -ray.d, wo;
        float pdfDirection = 0.f;
        if(!vr->SampleDirection(p, wi, wo, &pdfDirection, rng)) {
            // printf("return 1 \n");
            return Lv;
        }

        Ray r(p, wo, 0);

        // Sample a distance
        float pdfDistance = 0.f;
        float tDist;
        Point pSample;
        if(!vr->SampleDistance(r, &tDist, pSample, &pdfDistance, rng)) {
            // printf("return 2 \n");
            return Lv;
        }

        // Compute the transmittance
        pPrev = p;
        p = r(tDist);
        Ray tauRay(pPrev, p - pPrev, 0.f, 1.f, r.time, r.depth);
        Spectrum stepTau = vr->tau(tauRay, .5f * stepSize, rng.RandomFloat());
        Tr *= Exp(-stepTau);

        // Possibly terminate random walk if transmittance is small
        if (Tr.y() < 1e-3) {
            const float continueProb = .5f;
            if (rng.RandomFloat() > continueProb) {
                Tr = 0.f;
                // printf("return 3 \n");
                break;
            }
            Tr /= continueProb;
        }

        // Compute emission term at _p_
        Lv += Tr * vr->PhotonDensity(p) / (pdfDistance * pdfDirection);
    }

    // printf("%f %f %f %d \n", p.x, p.y, p.z, steps);

   // printf("%d, ", steps);
    return Lv;
}