distribution/piecewise_uniform.h
| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | /// @file | ||
| 2 | /// @brief Size-frequency distributions made of bands with diameters spread uniformly. | ||
| 3 | #pragma once | ||
| 4 | |||
| 5 | #include "terraingen/distribution/size_frequency.h" | ||
| 6 | |||
| 7 | #include <vector> | ||
| 8 | |||
| 9 | namespace terraingen { | ||
| 10 | |||
| 11 | /// One band of a piecewise uniform distribution: `density` features with diameters spread | ||
| 12 | /// uniformly over [`min`, `max`) metres. | ||
| 13 | struct UniformBand { | ||
| 14 | 4 | double min = 1.0; ///< Smallest diameter, metres; positive. | |
| 15 | 4 | double max = 2.0; ///< Largest diameter, metres; above `min`. | |
| 16 | 4 | double density = 0.01; ///< Features per m^2 (or per m^2 per Gyr), or a relative weight; >= 0. | |
| 17 | |||
| 18 | 4 | bool operator==(const UniformBand&) const = default; | |
| 19 | }; | ||
| 20 | |||
| 21 | /// A distribution made of diameter bands, each holding a number of features per m^2 with | ||
| 22 | /// diameters uniform across it, for scenes that set counts by size class instead of following a | ||
| 23 | /// power law. | ||
| 24 | /// | ||
| 25 | /// N(>=D) falls linearly across each band and is flat between bands; overlapping bands add. No | ||
| 26 | /// features are smaller than the smallest band or larger than the largest, so the valid range is | ||
| 27 | /// every diameter up to the largest band's `max`, and extrapolation beyond it, where N(>=D) is 0, | ||
| 28 | /// is allowed from the start. | ||
| 29 | class PiecewiseUniformSfd final : public SizeFrequencyDistribution { | ||
| 30 | public: | ||
| 31 | /// The distribution of `bands`. | ||
| 32 | /// @param total When positive, the features per m^2 (or per m^2 per Gyr) of all bands | ||
| 33 | /// together, shared in proportion to each band's `density`; 0 takes the densities as given. | ||
| 34 | /// @throws std::invalid_argument for no bands, a band whose diameters are not positive and | ||
| 35 | /// finite with `max` above `min`, a negative or non-finite density or total, or no features. | ||
| 36 | PiecewiseUniformSfd(std::vector<UniformBand> bands, SfdKind kind = SfdKind::Density, | ||
| 37 | double total = 0.0); | ||
| 38 | |||
| 39 | /// The bands, with densities per m^2 (or per m^2 per Gyr) after any `total` is applied. | ||
| 40 | 7 | const std::vector<UniformBand>& Bands() const { | |
| 41 | 7 | return bands_; | |
| 42 | } | ||
| 43 | |||
| 44 | protected: | ||
| 45 | double CumulativeAt(double diameter) const override; | ||
| 46 | double IncrementalAt(double diameter) const override; | ||
| 47 | double InvertCumulative(double target, double dMin, double dMax) const override; | ||
| 48 | |||
| 49 | private: | ||
| 50 | std::vector<UniformBand> bands_; | ||
| 51 | std::vector<double> edges_; | ||
| 52 | std::vector<double> edgeCumulative_; | ||
| 53 | }; | ||
| 54 | |||
| 55 | } // namespace terraingen | ||
| 56 |