/// <summary>
/// Calculates the strain for one difficulty type and stores it in <paramref name="obj"/>. This assumes that
/// <see cref="HitObject.Normpos"/> is already computed. This also sets <see cref="HitObject.IsSingle"/> if
/// <paramref name="type"/> is <seealso cref="StrainType.Speed"/>.
/// </summary>
private static void DiffStrain(StrainType type, HitObject obj, HitObject prev, double speedMul)
{
double value = 0.0;
double timeElapsed = (obj.Time - prev.Time) / speedMul;
double decay =
Math.Pow(DecayBase[type], timeElapsed / 1000.0);
obj.DeltaTime = timeElapsed;
/* this implementation doesn't account for sliders */
if ((obj.Type & (HitObjectType.Slider | HitObjectType.Circle)) != 0)
{
double distance = (obj.Normpos - prev.Normpos).Length;
obj.DeltaDistance = distance;
if (type == StrainType.Speed)
{
obj.IsSingle = distance > SingleSpacing;
}
value = DiffSpacingWeight(type, distance, timeElapsed, prev.DeltaDistance, prev.DeltaTime, obj.Angle);
value *= WeightScaling[type];
}
obj.Strains[type] = prev.Strains[type] * decay + value;
}
private static double DiffSpacingWeight(StrainType type, double distance)
{
switch (type)
{
case StrainType.Aim:
return(Math.Pow(distance, 0.99));
case StrainType.Speed:
if (distance > SingleSpacing)
{
return(2.5);
}
else if (distance > StreamSpacing)
{
return(1.6 + 0.9 * (distance - StreamSpacing) / (SingleSpacing - StreamSpacing));
}
else if (distance > AlmostDiameter)
{
return(1.2 + 0.4 * (distance - AlmostDiameter) / (StreamSpacing - AlmostDiameter));
}
else if (distance > AlmostDiameter / 2.0)
{
return(0.95 + 0.25 * (distance - AlmostDiameter / 2.0) / (AlmostDiameter / 2.0));
}
return(0.95);
default:
throw new InvalidOperationException("this difficulty type does not exist");
}
}
private double CalcIndividual(StrainType type)
{
strains.Clear();
double strainStep = StrainStep * speedMul;
double intervalEnd = strainStep;
double maxStrain = 0.0;
//calculate all strains
for (int i = 0; i < Beatmap.Objects.Count; ++i)
{
HitObject obj = Beatmap.Objects[i];
HitObject prev = i > 0
? Beatmap.Objects[i - 1]
: null;
if (prev != null)
{
DiffStrain(type, obj, prev, speedMul);
}
while (obj.Time > intervalEnd)
{
//add max strain for this interval
strains.Add(maxStrain);
if (prev != null)
{
//decay last object's strains until the next interval and use that as the initial max strain
double decay = Math.Pow(DecayBase[type], (intervalEnd - prev.Time) / 1000.0);
maxStrain = prev.Strains[type] * decay;
}
else
{
maxStrain = 0.0;
}
intervalEnd += strainStep;
}
maxStrain = Math.Max(maxStrain, obj.Strains[type]);
}
//weigh the top strains sorted from highest to lowest
double weight = 1.0;
double difficulty = 0.0;
strains.Sort();
strains.Reverse();
foreach (double strain in strains)
{
difficulty += strain * weight;
weight *= DecayWeight;
}
return(difficulty);
}
private static double DiffSpacingWeight(StrainType type, double distance,
double deltaTime,
double prevDistance, double prevDeltaTime,
double angle)
{
double angleBonus;
double strainTime = Math.Max(deltaTime, 50.0f);
switch (type)
{
case StrainType.Aim:
{
double result = 0;
double prevStrainTime = Math.Max(prevDeltaTime, 50.0f);
if (!(Double.IsNaN(angle) || Double.IsInfinity(angle)) && angle > AimAngleBonusBegin)
{
angleBonus = Math.Sqrt(
Math.Max(prevDistance - AngleBonusScale, 0)
* Math.Pow(Math.Sin(angle - AimAngleBonusBegin), 2)
* Math.Max(distance - AngleBonusScale, 0)
);
result = 1.5f * Math.Pow(Math.Max(0, angleBonus), 0.99)
/ Math.Max(AimTimingThreshold, prevStrainTime);
}
var weightedDistance = Math.Pow(distance, 0.99);
return(Math.Max(
result + weightedDistance /
Math.Max(AimTimingThreshold, strainTime),
weightedDistance / strainTime
));
}
case StrainType.Speed:
{
distance = Math.Min(distance, SingleSpacing);
deltaTime = Math.Max(deltaTime, MaxSpeedBonus);
double speedBonus = 1.0f;
if (deltaTime < MinSpeedBonus)
{
speedBonus += Math.Pow((MinSpeedBonus - deltaTime) / 40.0f, 2);
}
angleBonus = 1.0f;
if (!(Double.IsNaN(angle) || Double.IsInfinity(angle)) && angle < SpeedAngleBonusBegin)
{
double s = Math.Sin(1.5 * (SpeedAngleBonusBegin - angle));
angleBonus += Math.Pow(s, 2) / 3.57f;
if (angle < Math.PI / 2)
{
angleBonus = 1.28f;
if (distance < AngleBonusScale && angle < Math.PI / 4)
{
angleBonus += (1 - angleBonus)
* Math.Min((AngleBonusScale - distance) / 10, 1);
}
else if (distance < AngleBonusScale)
{
angleBonus += (1 - angleBonus)
* Math.Min((AngleBonusScale - distance) / 10, 1)
* Math.Sin((Math.PI / 2 - angle) * 4 / Math.PI);
}
}
}
return((
(1 + (speedBonus - 1) * 0.75f) *
angleBonus *
(0.95f + speedBonus * Math.Pow(distance / SingleSpacing, 3.5))
) / strainTime);
}
default:
throw new InvalidOperationException("this difficulty type does not exist");
}
}
