diff options
Diffstat (limited to 'src/powermap.cc')
| -rw-r--r-- | src/powermap.cc | 251 |
1 files changed, 251 insertions, 0 deletions
diff --git a/src/powermap.cc b/src/powermap.cc new file mode 100644 index 0000000..2bb45b7 --- /dev/null +++ b/src/powermap.cc @@ -0,0 +1,251 @@ +/* -*- Mode: c++ -*- */ +/*************************************************************************** + * powermap.cc + * + * Fri Apr 17 23:06:12 CEST 2020 + * Copyright 2020 André Nusser + * andre.nusser@googlemail.com + ****************************************************************************/ + +/* + * This file is part of DrumGizmo. + * + * DrumGizmo is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation; either version 3 of the License, or + * (at your option) any later version. + * + * DrumGizmo is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with DrumGizmo; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. + */ +#include "powermap.h" + +#include <cassert> +#include <cmath> + +namespace +{ + +using Power = Powermap::Power; +using PowerPair = Powermap::PowerPair; + +Power h00(Power x) +{ + return (1 + 2 * x) * pow(1 - x, 2); +} + +Power h10(Power x) +{ + return x * pow(1 - x, 2); +} + +Power h01(Power x) +{ + return x * x * (3 - 2 * x); +} + +Power h11(Power x) +{ + return x * x * (x - 1); +} + +Power computeValue(const Power x, const PowerPair& P0, const PowerPair& P1, + const Power m0, const Power m1) +{ + const auto x0 = P0.in; + const auto x1 = P1.in; + const auto y0 = P0.out; + const auto y1 = P1.out; + const auto dx = x1 - x0; + const auto x_prime = (x - x0)/dx; + + return + h00(x_prime) * y0 + + h10(x_prime) * dx * m0 + + h01(x_prime) * y1 + + h11(x_prime) * dx * m1; +} + +} // end anonymous namespace + +Powermap::Powermap() +{ + reset(); +} + +Power Powermap::map(Power in) +{ + assert(in >= 0. && in <= 1.); + + if (spline_needs_update) + { + updateSpline(); + } + + Power out; + if (in < fixed[0].in) + { + out = shelf ? fixed[0].out + : computeValue(in, {0.,0.}, fixed[0], m[0], m[1]); + } + else if (in < fixed[1].in) + { + out = computeValue(in, fixed[0], fixed[1], m[1], m[2]); + } + else if (in < fixed[2].in) + { + out = computeValue(in, fixed[1], fixed[2], m[2], m[3]); + } + else + { + // in >= fixed[2].in + out = shelf ? fixed[2].out + : computeValue(in, fixed[2], {1.,1.}, m[3], m[4]); + } + + assert(out >= 0. && out <= 1.); + return out; +} + +void Powermap::reset() +{ + setFixed0({eps, eps}); + setFixed1({.5, .5}); + setFixed2({1 - eps, 1 - eps}); + // FIXME: better false? + shelf = true; + + updateSpline(); +} + +void Powermap::setFixed0(PowerPair new_value) +{ + if (fixed[0] != new_value) + { + spline_needs_update = true; + fixed[0].in = clamp(new_value.in, eps, fixed[1].in - eps); + fixed[0].out = clamp(new_value.out, eps, fixed[1].out - eps); + } +} + +void Powermap::setFixed1(PowerPair new_value) +{ + if (fixed[1] != new_value) + { + spline_needs_update = true; + fixed[1].in = clamp(new_value.in, fixed[0].in + eps, fixed[2].in - eps); + fixed[1].out = clamp(new_value.out, fixed[0].out + eps, fixed[2].out - eps); + } +} + +void Powermap::setFixed2(PowerPair new_value) +{ + if (fixed[2] != new_value) + { + spline_needs_update = true; + fixed[2].in = clamp(new_value.in, fixed[1].in + eps, 1 - eps); + fixed[2].out = clamp(new_value.out, fixed[1].out + eps, 1 - eps); + } +} + +void Powermap::setShelf(bool enable) +{ + if (shelf != enable) + { + spline_needs_update = true; + this->shelf = enable; + } +} + +PowerPair Powermap::getFixed0() const +{ + return fixed[0]; +} + +PowerPair Powermap::getFixed1() const +{ + return fixed[1]; +} + +PowerPair Powermap::getFixed2() const +{ + return fixed[2]; +} + +// This mostly followes the wikipedia article for monotone cubic splines: +// https://en.wikipedia.org/wiki/Monotone_cubic_interpolation +void Powermap::updateSpline() +{ + assert(0. <= fixed[0].in && fixed[0].in < fixed[1].in && + fixed[1].in < fixed[2].in && fixed[2].in <= 1.); + assert(0. <= fixed[0].out && fixed[0].out <= fixed[1].out && + fixed[1].out <= fixed[2].out && fixed[2].out <= 1.); + + Powers X = shelf ? Powers{fixed[0].in, fixed[1].in, fixed[2].in} + : Powers{0., fixed[0].in, fixed[1].in, fixed[2].in, 1.}; + Powers Y = shelf ? Powers{fixed[0].out, fixed[1].out, fixed[2].out} + : Powers{0., fixed[0].out, fixed[1].out, fixed[2].out, 1.}; + + auto slopes = calcSlopes(X, Y); + + if (shelf) + { + assert(slopes.size() == 3); + this->m[1] = slopes[0]; + this->m[2] = slopes[1]; + this->m[3] = slopes[2]; + } + else + { + assert(slopes.size() == 5); + for (std::size_t i = 0; i < m.size(); ++i) + { + this->m[i] = slopes[i]; + } + } + + spline_needs_update = false; +} + +// This follows the monotone cubic spline algorithm of Steffen, from: +// "A Simple Method for Monotonic Interpolation in One Dimension" +std::vector<float> Powermap::calcSlopes(const Powers& X, const Powers& Y) +{ + Powers m(X.size()); + + Powers d(X.size() - 1); + Powers h(X.size() - 1); + for (std::size_t i = 0; i < d.size(); ++i) + { + h[i] = X[i + 1] - X[i]; + d[i] = (Y[i + 1] - Y[i]) / h[i]; + } + + m.front() = d.front(); + for (std::size_t i = 1; i < m.size() - 1; ++i) + { + m[i] = (d[i - 1] + d[i]) / 2.; + } + m.back() = d.back(); + + for (std::size_t i = 1; i < m.size() - 1; ++i) + { + const auto min_d = 2*std::min(d[i - 1], d[i]); + m[i] = + std::min<float>(min_d, + (h[i] * d[i - 1] + h[i - 1] * d[i]) / (h[i - 1] + h[i])); + } + + return m; +} + +Power Powermap::clamp(Power in, Power min, Power max) const +{ + return std::max(min, std::min(in, max)); +} |