/// <summary>
/// Map over the fraction of the sun's disk visible times Cos(theta) - theta is the angle between the sun and normal
/// </summary>
/// <param name="line"></param>
/// <param name="sample"></param>
/// <param name="start"></param>
/// <param name="stop"></param>
/// <param name="step"></param>
/// <param name="action"></param>
/// <returns></returns>
public bool MapOverSunContribution(int line, int sample, DateTime start, DateTime stop, TimeSpan step, Action <DateTime, float> action)
{
var id = TerrainPatch.LineSampleToId(line, sample);
var patch = GetPatch(id);
if (patch == null)
{
return(false);
}
var cross = GetSurfaceNormal(line, sample);
var y_offset = line - patch.Line;
var x_offset = sample - patch.Sample;
var mat = patch.Matrices[y_offset][x_offset];
var horizon = patch.Horizons[y_offset][x_offset];
if (!horizon.IsDegrees)
{
lock (horizon)
horizon.ConvertSlopeToDegrees();
}
var cache = SunVectorCache.GetSingleton();
var temp = new Vector3d();
for (var time = start; time <= stop; time += step)
{
var sunvec = cache.SunPosition(time);
TerrainPatch.Transform(ref sunvec, ref mat, ref temp);
var sun_x = temp[0];
var sun_y = temp[1];
var sun_z = temp[2];
var azimuth_rad = Math.Atan2(sun_y, sun_x) + Math.PI; // [0,2PI]
var azimuth_deg = (float)(azimuth_rad * 180d / Math.PI);
var alen = Math.Sqrt(sun_x * sun_x + sun_y * sun_y);
var slope = sun_z / alen;
var elevation_deg = ((float)Math.Atan(slope)) * 180f / 3.141592653589f;
var sunfrac = horizon.SunFraction2(azimuth_deg, elevation_deg);
//if (line == 17522 && sample == 12388)
//{
// Console.WriteLine($"{line},{sample}, time={time} elevation_deg={elevation_deg} sun={sunfrac}");
//}
sunvec.NormalizeFast(); // Normalize before calculating surface temp
var dot = Vector3d.Dot(sunvec, cross);
var sun_contrib = dot < 0d ? 0d : sunfrac * dot;
//if (sun_contrib > 0)
// Console.WriteLine(sun_contrib);
action(time, (float)sun_contrib);
}
return(true);
}
public static SunVectorCache GetSingleton() => _singleton != null ? _singleton : _singleton = new SunVectorCache();