Spectrum DiffusePRTIntegrator::Li(const Scene *scene, const Renderer *,
const RayDifferential &ray, const Intersection &isect,
const Sample *sample, MemoryArena &arena) const {
Spectrum L = 0.f;
Vector wo = -ray.d;
// Compute emitted light if ray hit an area light source
L += isect.Le(wo);
// Evaluate BSDF at hit point
BSDF *bsdf = isect.GetBSDF(ray, arena);
const Point &p = bsdf->dgShading.p;
const Normal &n = bsdf->dgShading.nn;
// Compute reflected radiance using diffuse PRT
// Project diffuse transfer function at point to SH
Spectrum *c_transfer = arena.Alloc<Spectrum>(SHTerms(lmax));
SHComputeDiffuseTransfer(p, Faceforward(n, wo), isect.rayEpsilon,
scene, *sample->rng, nSamples, lmax, c_transfer);
// Compute integral of product of incident radiance and transfer function
Spectrum LT = 0.f;
for (int i = 0; i < SHTerms(lmax); ++i)
LT += c_in[i] * c_transfer[i];
// Compute reflectance at point for diffuse transfer
const int sqrtRhoSamples = 6;
float rhoRSamples[2*sqrtRhoSamples*sqrtRhoSamples];
StratifiedSample2D(rhoRSamples, sqrtRhoSamples, sqrtRhoSamples, *sample->rng);
Spectrum Kd = bsdf->rho(wo, sqrtRhoSamples*sqrtRhoSamples, rhoRSamples,
BSDF_ALL_REFLECTION) * INV_PI;
return L + Kd * LT.Clamp();
}
Spectrum operator()(float d2) const {
Spectrum dpos = Sqrt(Spectrum(d2) + zpos * zpos);
Spectrum dneg = Sqrt(Spectrum(d2) + zneg * zneg);
Spectrum Rd = (1.f / (4.f * M_PI)) *
((zpos * (dpos * sigma_tr + Spectrum(1.f)) *
Exp(-sigma_tr * dpos)) / (dpos * dpos * dpos) -
(zneg * (dneg * sigma_tr + Spectrum(1.f)) *
Exp(-sigma_tr * dneg)) / (dneg * dneg * dneg));
return Rd.Clamp();
}
Spectrum UseRadianceProbes::Li(const Scene *scene, const Renderer *renderer,
const RayDifferential &ray, const Intersection &isect,
const Sample *sample, RNG &rng, MemoryArena &arena, int wavelength) const {
Spectrum L(0.);
Vector wo = -ray.d;
// Compute emitted light if ray hit an area light source
L += isect.Le(wo);
// Evaluate BSDF at hit point
BSDF *bsdf = isect.GetBSDF(ray, arena, wavelength);
const Point &p = bsdf->dgShading.p;
const Normal &n = bsdf->dgShading.nn;
// Compute reflection for radiance probes integrator
if (!includeDirectInProbes)
L += UniformSampleAllLights(scene, renderer, arena, p, n,
wo, isect.rayEpsilon, ray.time, bsdf, sample, rng,
lightSampleOffsets, bsdfSampleOffsets);
// Compute reflected lighting using radiance probes
// Compute probe coordinates and offsets for lookup point
Vector offset = bbox.Offset(p);
float voxx = (offset.x * nProbes[0]) - 0.5f;
float voxy = (offset.y * nProbes[1]) - 0.5f;
float voxz = (offset.z * nProbes[2]) - 0.5f;
int vx = Floor2Int(voxx), vy = Floor2Int(voxy), vz = Floor2Int(voxz);
float dx = voxx - vx, dy = voxy - vy, dz = voxz - vz;
// Get radiance probe coefficients around lookup point
const Spectrum *b000 = c_inXYZ(lmax, vx, vy, vz);
const Spectrum *b100 = c_inXYZ(lmax, vx+1, vy, vz);
const Spectrum *b010 = c_inXYZ(lmax, vx, vy+1, vz);
const Spectrum *b110 = c_inXYZ(lmax, vx+1, vy+1, vz);
const Spectrum *b001 = c_inXYZ(lmax, vx, vy, vz+1);
const Spectrum *b101 = c_inXYZ(lmax, vx+1, vy, vz+1);
const Spectrum *b011 = c_inXYZ(lmax, vx, vy+1, vz+1);
const Spectrum *b111 = c_inXYZ(lmax, vx+1, vy+1, vz+1);
// Compute incident radiance from radiance probe coefficients
Spectrum *c_inp = arena.Alloc<Spectrum>(SHTerms(lmax));
for (int i = 0; i < SHTerms(lmax); ++i) {
// Do trilinear interpolation to compute SH coefficients at point
Spectrum c00 = Lerp(dx, b000[i], b100[i]);
Spectrum c10 = Lerp(dx, b010[i], b110[i]);
Spectrum c01 = Lerp(dx, b001[i], b101[i]);
Spectrum c11 = Lerp(dx, b011[i], b111[i]);
Spectrum c0 = Lerp(dy, c00, c10);
Spectrum c1 = Lerp(dy, c01, c11);
c_inp[i] = Lerp(dz, c0, c1);
}
// Convolve incident radiance to compute irradiance function
Spectrum *c_E = arena.Alloc<Spectrum>(SHTerms(lmax));
SHConvolveCosTheta(lmax, c_inp, c_E);
// Evaluate irradiance function and accumulate reflection
Spectrum rho = bsdf->rho(wo, rng, BSDF_ALL_REFLECTION);
float *Ylm = ALLOCA(float, SHTerms(lmax));
SHEvaluate(Vector(Faceforward(n, wo)), lmax, Ylm);
Spectrum E = 0.f;
for (int i = 0; i < SHTerms(lmax); ++i)
E += c_E[i] * Ylm[i];
L += rho * INV_PI * E.Clamp();
return L;
}
Spectrum GlossyPRTIntegrator::Li(const Scene *scene, const Renderer *,
const RayDifferential &ray, const Intersection &isect,
const Sample *sample, RNG &rng, MemoryArena &arena) const {
Spectrum L = 0.f;
Vector wo = -ray.d;
// Compute emitted light if ray hit an area light source
L += isect.Le(wo);
// Evaluate BSDF at hit point
BSDF *bsdf = isect.GetBSDF(ray, arena);
const Point &p = bsdf->dgShading.p;
// Compute reflected radiance with glossy PRT at point
// Compute SH radiance transfer matrix at point and SH coefficients
Spectrum *c_t = arena.Alloc<Spectrum>(SHTerms(lmax));
Spectrum *T = arena.Alloc<Spectrum>(SHTerms(lmax)*SHTerms(lmax));
SHComputeTransferMatrix(p, isect.rayEpsilon, scene, rng, nSamples,
lmax, T);
SHMatrixVectorMultiply(T, c_in, c_t, lmax);
// Rotate incident SH lighting to local coordinate frame
Vector r1 = bsdf->LocalToWorld(Vector(1,0,0));
Vector r2 = bsdf->LocalToWorld(Vector(0,1,0));
Normal nl = Normal(bsdf->LocalToWorld(Vector(0,0,1)));
Matrix4x4 rot(r1.x, r2.x, nl.x, 0,
r1.y, r2.y, nl.y, 0,
r1.z, r2.z, nl.z, 0,
0, 0, 0, 1);
Spectrum *c_l = arena.Alloc<Spectrum>(SHTerms(lmax));
SHRotate(c_t, c_l, rot, lmax, arena);
#if 0
// Sample BSDF and integrate against direct SH coefficients
float *Ylm = ALLOCA(float, SHTerms(lmax));
int ns = 1024;
for (int i = 0; i < ns; ++i) {
Vector wi;
float pdf;
Spectrum f = bsdf->Sample_f(wo, &wi, BSDFSample(rng), &pdf);
if (pdf > 0.f && !f.IsBlack() && !scene->IntersectP(Ray(p, wi))) {
f *= fabsf(Dot(wi, n)) / (pdf * ns);
SHEvaluate(bsdf->WorldToLocal(wi), lmax, Ylm);
Spectrum Li = 0.f;
for (int j = 0; j < SHTerms(lmax); ++j)
Li += Ylm[j] * c_l[j] * f;
L += Li.Clamp();
}
}
#else
// Compute final coefficients _c\_o_ using BSDF matrix
Spectrum *c_o = arena.Alloc<Spectrum>(SHTerms(lmax));
SHMatrixVectorMultiply(B, c_l, c_o, lmax);
// Evaluate outgoing radiance function for $\wo$ and add to _L_
Vector woLocal = bsdf->WorldToLocal(wo);
float *Ylm = ALLOCA(float, SHTerms(lmax));
SHEvaluate(woLocal, lmax, Ylm);
Spectrum Li = 0.f;
for (int i = 0; i < SHTerms(lmax); ++i)
Li += Ylm[i] * c_o[i];
L += Li.Clamp();
#endif
return L;
}
COREDLL Spectrum FresnelApproxK(const Spectrum &Fr) {
Spectrum reflectance = Fr.Clamp(0.f, .999f);
return 2.f * (reflectance /
(Spectrum(1.) - reflectance)).Sqrt();
}
COREDLL Spectrum FresnelApproxEta(const Spectrum &Fr) {
Spectrum reflectance = Fr.Clamp(0.f, .999f);
return (Spectrum(1.) + reflectance.Sqrt()) /
(Spectrum(1.) - reflectance.Sqrt());
}
Spectrum FresnelApproxK(const Spectrum &Fr) {
const Spectrum reflectance = Fr.Clamp(0.f, .999f);
return 2.f * Sqrt(reflectance /
(Spectrum(1.f) - reflectance));
}
Spectrum FresnelApproxN(const Spectrum &Fr) {
const Spectrum sqrtReflectance = Fr.Clamp(0.f, .999f).Sqrt();
return (Spectrum(1.f) + sqrtReflectance) /
(Spectrum(1.f) - sqrtReflectance);
}