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/* Distribution.cpp
Copyright (c) 2022 by DeBlister
Endless Sky is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later version.
Endless Sky 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 General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "Distribution.h"
#include "Angle.h"
#include "Random.h"
#include <vector>
using namespace std;
namespace {
double ManipulateNormal(double smoothness, bool inverted)
{
// Center values within [0, 1] so that fractional retention begins to accumulate
// at the endpoints (rather than at the center) of the distribution.
double randomFactor = Random::Normal(.5, smoothness);
// Retain only the fractional information, to keep all absolute values within [0, 1].
randomFactor = randomFactor - static_cast<int64_t>(randomFactor);
// Shift negative values into [0, 1] to create redundancy at the endpoints
if(randomFactor < 0.)
++randomFactor;
// Invert probabilities so that endpoints are most probable.
if(inverted)
{
if(randomFactor > .5)
randomFactor -= .5;
else if(randomFactor < .5)
randomFactor += .5;
}
// Transform from [0, 1] to [-1, 1] so that the return value can be simply used.
randomFactor *= 2;
--randomFactor;
return randomFactor;
}
// These values are paired with Distribution::Types; any change in one should be made in the other.
const double SMOOTHNESS_TABLE[] = {.13, .234, .314};
}
Angle Distribution::GenerateInaccuracy(double value, pair<Type, bool> distribution)
{
// Check if there is any inaccuracy to apply
if(!value)
return Angle();
switch(distribution.first)
{
case Type::Uniform:
return Angle(2 * (Random::Real() - .5) * value);
case Type::Narrow:
case Type::Medium:
case Type::Wide:
return Angle(value * ManipulateNormal(SMOOTHNESS_TABLE[static_cast<int>(distribution.first)],
distribution.second));
case Type::Triangular:
default:
return Angle((Random::Real() - Random::Real()) * value);
}
}
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