static void RDFtoRP(const Curve &rdf, int npoints, Curve *rp) {
const float wstep = 1.f / sqrtf(npoints);
Curve tmp(rdf);
for (int i = 0; i < rp->size(); ++i) {
const float u0 = rp->ToX(i);
const float u = TWOPI * u0;
const float wndsize = rdf.x1 * std::min(0.5f, std::max(0.2f, 4.f * u0 * wstep));
for (int j = 0; j < tmp.size(); ++j) {
float x = rdf.ToX(j);
float wnd = BlackmanWindow(x, wndsize);
tmp[j] = (rdf[j] - 1) * j0f(u*x) * x * wnd;
}
(*rp)[i] = fabsf(1.f + TWOPI * Integrate(tmp) * npoints);
}
}
static float OscillationsMetric(const Curve &rp, int npoints) {
// nuosci: lowest frequency v for which P(v) ~ 1
float nuosci = 0.0, maxp = 0.0;
for (int i = 0; i < rp.size() && maxp < 0.98; ++i) {
float p = rp[i];
if (p > maxp) {
maxp = p;
nuosci = rp.ToX(i);
}
}
float npeaks = 10.f;
float maxfreq = sqrtf(npoints) / 2;
float x0 = nuosci;
float x1 = std::min(x0 + npeaks * maxfreq, rp.x1);
Curve osci(rp);
for (int i = 0; i < osci.size(); ++i) {
float nu = osci.ToX(i);
osci[i] = nu < x0 ? 0.f : (osci[i] - 1.f) * (osci[i] - 1.f) * nu;
}
return 10.f * sqrtf(TWOPI * Integrate(osci, x0, x1) / RingArea(x0, x1));
}