/// Generate a histogram of the BSDF density function via MC sampling
void FrequencyTable(const BSDF* bsdf, const Vector3f& wo, RNG& rng,
int sampleCount, int thetaRes, int phiRes, Float* target) {
memset(target, 0, thetaRes * phiRes * sizeof(Float));
Float factorTheta = thetaRes / Pi, factorPhi = phiRes / (2 * Pi);
BxDFType flags;
Vector3f wi;
Float pdf;
for (int i = 0; i < sampleCount; ++i) {
Point2f sample {rng.UniformFloat(), rng.UniformFloat()};
Spectrum f = bsdf->Sample_f(wo, &wi, sample, &pdf, BSDF_ALL, &flags);
if (f == Spectrum() || (flags & BSDF_SPECULAR)) continue;
Vector3f wiL = bsdf->WorldToLocal(wi);
Point2f coords(std::acos(Clamp(wiL.z, -1, 1)) * factorTheta,
std::atan2(wiL.y, wiL.x) * factorPhi);
if (coords.y < 0) coords.y += 2 * Pi * factorPhi;
int thetaBin =
std::min(std::max(0, (int)std::floor(coords.x)), thetaRes - 1);
int phiBin =
std::min(std::max(0, (int)std::floor(coords.y)), phiRes - 1);
target[thetaBin * phiRes + phiBin] += 1;
}
}
void Gen_Sample_f(BSDF* bsdf, const Vector3f& wo, Vector3f* wi, Float* pdf,
Spectrum* f) {
// only glossy or diffuse reflections (no specular reflections)
BxDFType inflags = BxDFType(BSDF_REFLECTION | BSDF_DIFFUSE | BSDF_GLOSSY);
BxDFType outflags;
Point2f sample(rng.UniformFloat(), rng.UniformFloat());
*f = bsdf->Sample_f(wo, wi, sample, pdf, inflags, &outflags);
// double check bsdf->Pdf() gives us the same answer
Vector3f wiL = bsdf->WorldToLocal(*wi);
float wiCosTheta = wiL.z;
bool validSample = (wiCosTheta > 1e-7);
if (validSample) {
float verifyPdf = bsdf->Pdf(wo, *wi, inflags);
float relErr = fabs(verifyPdf - *pdf) / *pdf;
if (relErr > 1e-3) {
fprintf(stderr,
"BSDF::Pdf() doesn't match BSDF::Sample_f() !\n"
" Sample_f pdf %.3f, Pdf pdf %.3f (rel error %f)\n"
" wo %.3f %.3f %.3f, wi %.3f %.3f %.3f\n",
*pdf, verifyPdf, relErr, wo[0], wo[1], wo[2], (*wi)[0],
(*wi)[1], (*wi)[2]);
fprintf(
stderr,
"blah! validSample %d, wiCosTheta %.3f, wiL %.3f %.3f %.3f\n",
validSample, wiCosTheta, wiL[0], wiL[1], wiL[2]);
}
}
}
TEST(EXR, Randoms) {
int width = 1024;
int height = 1024;
RNG rng;
float *buf = new float[4 * width * height];
for (int i = 0; i < 4 * width * height; ++i) {
buf[i] = -20 + 20. * rng.UniformFloat();
}
EXRImage image;
image.num_channels = 4;
const char *channels[] = { "B", "G", "R", "A" };
image.channel_names = channels;
unsigned char *images[] = { (unsigned char *)buf,
(unsigned char *)(buf + width * height),
(unsigned char *)(buf + 2 * width * height),
(unsigned char *)(buf + 3 * width * height) };
image.images = images;
int pixel_types[] = { TINYEXR_PIXELTYPE_HALF, TINYEXR_PIXELTYPE_HALF,
TINYEXR_PIXELTYPE_HALF, TINYEXR_PIXELTYPE_HALF };
image.pixel_types = pixel_types;
image.width = width;
image.height = height;
const char *err = nullptr;
EXPECT_EQ(0, SaveMultiChannelEXRToFile(&image, "test.exr", &err)) << err;
EXRImage readImage;
EXPECT_EQ(0, LoadMultiChannelEXRFromFile(&readImage, "test.exr", &err))
<< err;
CompareImages(image, readImage, true);
}
// Sampling Function Definitions
void StratifiedSample1D(Float *samp, int nSamples, RNG &rng, bool jitter) {
Float invNSamples = (Float)1 / nSamples;
for (int i = 0; i < nSamples; ++i) {
Float delta = jitter ? rng.UniformFloat() : 0.5f;
samp[i] = std::min((i + delta) * invNSamples, OneMinusEpsilon);
}
}
Point2f RejectionSampleDisk(RNG &rng) {
Point2f p;
do {
p.x = 1 - 2 * rng.UniformFloat();
p.y = 1 - 2 * rng.UniformFloat();
} while (p.x * p.x + p.y * p.y > 1);
return p;
}
void RealisticCamera::TestExitPupilBounds() const {
Float filmDiagonal = film->diagonal;
static RNG rng;
Float u = rng.UniformFloat();
Point3f pFilm(u * filmDiagonal / 2, 0, 0);
Float r = pFilm.x / (filmDiagonal / 2);
int pupilIndex =
std::min((int)exitPupilBounds.size() - 1,
(int)std::floor(r * (exitPupilBounds.size() - 1)));
Bounds2f pupilBounds = exitPupilBounds[pupilIndex];
if (pupilIndex + 1 < (int)exitPupilBounds.size())
pupilBounds = Union(pupilBounds, exitPupilBounds[pupilIndex + 1]);
// Now, randomly pick points on the aperture and see if any are outside
// of pupil bounds...
for (int i = 0; i < 1000; ++i) {
Point2f pd = ConcentricSampleDisk(
Point2f(rng.UniformFloat(), rng.UniformFloat()));
pd *= RearElementRadius();
Ray testRay(pFilm, Point3f(pd.x, pd.y, 0.f) - pFilm);
Ray testOut;
if (!TraceLensesFromFilm(testRay, &testOut)) continue;
if (!Inside(pd, pupilBounds)) {
fprintf(stderr,
"Aha! (%f,%f) went through, but outside bounds (%f,%f) - "
"(%f,%f)\n",
pd.x, pd.y, pupilBounds.pMin[0], pupilBounds.pMin[1],
pupilBounds.pMax[0], pupilBounds.pMax[1]);
RenderExitPupil(
(Float)pupilIndex / exitPupilBounds.size() * filmDiagonal / 2.f,
0.f, "low.exr");
RenderExitPupil((Float)(pupilIndex + 1) / exitPupilBounds.size() *
filmDiagonal / 2.f,
0.f, "high.exr");
RenderExitPupil(pFilm.x, 0.f, "mid.exr");
exit(0);
}
}
fprintf(stderr, ".");
}
void Gen_UniformHemisphere(BSDF* bsdf, const Vector3f& wo, Vector3f* wi,
Float* pdf, Spectrum* f) {
float u1 = rng.UniformFloat();
float u2 = rng.UniformFloat();
Vector3f wiL = UniformSampleHemisphere(Point2f(u1, u2));
*wi = bsdf->LocalToWorld(wiL);
*pdf = UniformHemispherePdf();
*f = bsdf->f(wo, *wi);
}
void StratifiedSample2D(Point2f *samp, int nx, int ny, RNG &rng, bool jitter) {
Float dx = (Float)1 / nx, dy = (Float)1 / ny;
for (int y = 0; y < ny; ++y)
for (int x = 0; x < nx; ++x) {
Float jx = jitter ? rng.UniformFloat() : 0.5f;
Float jy = jitter ? rng.UniformFloat() : 0.5f;
samp->x = std::min((x + jx) * dx, OneMinusEpsilon);
samp->y = std::min((y + jy) * dy, OneMinusEpsilon);
++samp;
}
}
void Gen_CosHemisphere(BSDF* bsdf, const Vector3f& wo, Vector3f* wi, Float* pdf,
Spectrum* f) {
float u1 = rng.UniformFloat();
float u2 = rng.UniformFloat();
Vector3f wiL = CosineSampleHemisphere(Point2f(u1, u2));
*wi = bsdf->LocalToWorld(wiL);
float cosTheta = wiL.z;
*pdf = CosineHemispherePdf(cosTheta);
*f = bsdf->f(wo, *wi);
}
void LatinHypercube(Float *samples, int nSamples, int nDim, RNG &rng) {
// Generate LHS samples along diagonal
Float invNSamples = (Float)1 / nSamples;
for (int i = 0; i < nSamples; ++i)
for (int j = 0; j < nDim; ++j) {
Float sj = (i + (rng.UniformFloat())) * invNSamples;
samples[nDim * i + j] = std::min(sj, OneMinusEpsilon);
}
// Permute LHS samples in each dimension
for (int i = 0; i < nDim; ++i) {
for (int j = 0; j < nSamples; ++j) {
int other = j + rng.UniformUInt32(nSamples - j);
std::swap(samples[nDim * j + i], samples[nDim * other + i]);
}
}
}
void TestBSDF(void (*createBSDF)(BSDF*, MemoryArena&),
const char* description) {
MemoryArena arena;
Options opt;
pbrtInit(opt);
const int thetaRes = CHI2_THETA_RES;
const int phiRes = CHI2_PHI_RES;
const int sampleCount = CHI2_SAMPLECOUNT;
Float* frequencies = new Float[thetaRes * phiRes];
Float* expFrequencies = new Float[thetaRes * phiRes];
RNG rng;
int index = 0;
std::cout.precision(3);
// Create BSDF, which requires creating a Shape, casting a Ray that
// hits the shape to get a SurfaceInteraction object.
BSDF* bsdf = nullptr;
Transform t = RotateX(-90);
Transform tInv = Inverse(t);
{
bool reverseOrientation = false;
ParamSet p;
std::shared_ptr<Shape> disk(
new Disk(&t, &tInv, reverseOrientation, 0., 1., 0, 360.));
Point3f origin(0.1, 1,
0); // offset slightly so we don't hit center of disk
Vector3f direction(0, -1, 0);
Float tHit;
Ray r(origin, direction);
SurfaceInteraction isect;
disk->Intersect(r, &tHit, &isect);
bsdf = ARENA_ALLOC(arena, BSDF)(isect);
createBSDF(bsdf, arena);
}
for (int k = 0; k < CHI2_RUNS; ++k) {
/* Randomly pick an outgoing direction on the hemisphere */
Point2f sample {rng.UniformFloat(), rng.UniformFloat()};
Vector3f woL = CosineSampleHemisphere(sample);
Vector3f wo = bsdf->LocalToWorld(woL);
FrequencyTable(bsdf, wo, rng, sampleCount, thetaRes, phiRes,
frequencies);
IntegrateFrequencyTable(bsdf, wo, sampleCount, thetaRes, phiRes,
expFrequencies);
std::string filename = StringPrintf("/tmp/chi2test_%s_%03i.m",
description, ++index);
DumpTables(frequencies, expFrequencies, thetaRes, phiRes,
filename.c_str());
auto result =
Chi2Test(frequencies, expFrequencies, thetaRes, phiRes, sampleCount,
CHI2_MINFREQ, CHI2_SLEVEL, CHI2_RUNS);
EXPECT_TRUE(result.first) << result.second << ", iteration " << k;
}
delete[] frequencies;
delete[] expFrequencies;
pbrtCleanup();
}
