/// <summary>
/// Generates a new set of precipitation and snowfall map images.
/// </summary>
/// <param name="planet">The planet being mapped.</param>
/// <param name="winterTemperatures">A winter temperature map.</param>
/// <param name="summerTemperatues">A summer temperature map.</param>
/// <param name="resolution">The vertical resolution.</param>
/// <param name="steps">
/// The number of maps to generate internally (representing evenly spaced "seasons" during a year,
/// starting and ending at the winter solstice in the northern hemisphere).
/// </param>
/// <param name="temperatureProjection">
/// <para>
/// The map projection of the temperature maps. They must be the same.
/// </para>
/// <para>
/// If left <see langword="null"/> an equirectangular projection of the full globe is
/// assumed.
/// </para>
/// </param>
/// <param name="projection">
/// <para>
/// The map projection options used.
/// </para>
/// <para>
/// If left <see langword="null"/> an equirectangular projection of the full globe is
/// produced.
/// </para>
/// </param>
/// <returns>
/// A set of precipitation and snowfall map images. Pixel luminosity indicates
/// precipitation in mm/hr, relative to the <see cref="Atmosphere.MaxPrecipitation"/> of
/// this planet's <see cref="Atmosphere"/>.
/// </returns>
public static (Image <L16>[] precipitationMaps, Image <L16>[] snowfallMaps) GetPrecipitationAndSnowfallMaps(
this Planetoid planet,
Image <L16> winterTemperatures,
Image <L16> summerTemperatues,
int resolution,
int steps,
MapProjectionOptions?temperatureProjection = null,
MapProjectionOptions?projection = null)
{
var options = projection ?? MapProjectionOptions.Default;
var precipitationMaps = new Image <L16> [steps];
var snowMaps = new Image <L16> [steps];
if (planet.Atmosphere.MaxPrecipitation.IsNearlyZero())
{
var xResolution = (int)Math.Floor(resolution * options.AspectRatio);
for (var i = 0; i < steps; i++)
{
precipitationMaps[i] = new Image <L16>(xResolution, resolution);
snowMaps[i] = new Image <L16>(xResolution, resolution);
}
return(precipitationMaps, snowMaps);
}
var noise1 = new FastNoise(planet.Seed4, 1.0, FastNoise.NoiseType.Simplex);
var noise2 = new FastNoise(planet.Seed5, 3.0, FastNoise.NoiseType.SimplexFractal, octaves: 3);
var proportionOfYear = 1f / steps;
var proportionOfYearAtMidpoint = 0f;
var trueAnomaly = planet.WinterSolsticeTrueAnomaly;
var trueAnomalyPerSeason = DoubleConstants.TwoPi / steps;
for (var i = 0; i < steps; i++)
{
var solarDeclination = planet.GetSolarDeclination(trueAnomaly);
(precipitationMaps[i], snowMaps[i]) = SurfaceMapImage.GenerateMapImages(
new[] { winterTemperatures, summerTemperatues },
(lat, lon, temperature) =>
{
var precipitation = planet.GetPrecipitationNoise(
noise1,
noise2,
planet.LatitudeAndLongitudeToDoubleVector(lat, lon),
lat,
Planetoid.GetSeasonalLatitudeFromDeclination(lat, solarDeclination),
temperature * SurfaceMapImage.TemperatureScaleFactor,
out var snow);
return(
precipitation / planet.Atmosphere.MaxPrecipitation,
snow / planet.Atmosphere.MaxSnowfall);
},
