layers/craters/ages/steady_state.h

Line	Exec	Source
1		/// @file
2		/// @brief Crater ages on surfaces where small craters are in equilibrium.
3		#pragma once
4
5		#include "terraingen/distribution/production_surface.h"
6		#include "terraingen/distribution/size_frequency.h"
7		#include "terraingen/layers/craters/ages/age_model.h"
8
9		#include <memory>
10
11		namespace terraingen {
12
13		/// Ages of craters on a surface `ageGyr` old where small craters are in equilibrium.
14		///
15		/// A crater's lifetime is tau(D) = n_eq(D) / n_prod(D), capped at the surface age; ages follow the
16		/// formation rate of `chronology` over [0, lifetime].
17		class SteadyStateAges final : public CraterAgeModel {
18		public:
19		/// @param productionRate A `ProductionRate` distribution, such as
20		/// `ExtendedNeukumProductionFunction`.
21		/// @param equilibrium A `Density` distribution, such as `TraskEquilibrium`.
22		/// @param ageGyr Surface age in Gyr.
23		/// @param chronology N(>=1 km) per m^2 by age, such as `NeukumLunarChronology`; ages are drawn
24		/// in proportion to its rate.
25		/// @throws std::invalid_argument for null or mismatched kinds, or an empty `chronology`.
26		/// @throws std::domain_error if `chronology` rejects `ageGyr`.
27		SteadyStateAges(std::shared_ptr<const SizeFrequencyDistribution> productionRate,
28		std::shared_ptr<const SizeFrequencyDistribution> equilibrium, double ageGyr,
29		Chronology chronology);
30
31		/// The surface age in Gyr.
32	5	double SurfaceAgeGyr() const {
33	5	return ageGyr_;
34		}
35
36		/// The equilibrium lifetime tau(D) in Gyr of craters of `diameter` metres, before capping at
37		/// the surface age.
38		/// @throws std::domain_error outside either distribution's valid range.
39		double EquilibriumLifetimeGyr(double diameter) const;
40
41		protected:
42		double LifetimeAt(double diameter) const override;
43		double SampleAgeAt(RandomStream& random, double diameter, double lifetimeGyr) const override;
44
45		private:
46		std::shared_ptr<const SizeFrequencyDistribution> productionRate_;
47		std::shared_ptr<const SizeFrequencyDistribution> equilibrium_;
48		double ageGyr_;
49		Chronology chronology_;
50		};
51
52		} // namespace terraingen
53

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