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Add difficulty calculation

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Adds base classes for difficulty calculations, hooks them up with
carousel container, and adds a port of the osu difficulty calculator.
This commit is contained in:
Thomas Müller
2017-02-19 17:41:51 +01:00
parent 5721e7f2d2
commit 417f146386
29 changed files with 587 additions and 31 deletions
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osu.Game.Modes.Osu/Objects/OsuHitObjectDifficulty.cs Normal file
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// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
using OpenTK;
using System;
using System.Diagnostics;
using System.Linq;
namespace osu.Game.Modes.Osu.Objects
{
class OsuHitObjectDifficulty
{
/// <summary>
/// Factor by how much speed / aim strain decays per second.
/// </summary>
/// <remarks>
/// These values are results of tweaking a lot and taking into account general feedback.
/// Opinionated observation: Speed is easier to maintain than accurate jumps.
/// </remarks>
internal static readonly double[] DECAY_BASE = { 0.3, 0.15 };
/// <summary>
/// Pseudo threshold values to distinguish between "singles" and "streams"
/// </summary>
/// <remarks>
/// Of course the border can not be defined clearly, therefore the algorithm has a smooth transition between those values.
/// They also are based on tweaking and general feedback.
/// </remarks>
private const double STREAM_SPACING_TRESHOLD = 110,
SINGLE_SPACING_TRESHOLD = 125;
/// <summary>
/// Scaling values for weightings to keep aim and speed difficulty in balance.
/// </summary>
/// <remarks>
/// Found from testing a very large map pool (containing all ranked maps) and keeping the average values the same.
/// </remarks>
private static readonly double[] SPACING_WEIGHT_SCALING = { 1400, 26.25 };
/// <summary>
/// Almost the normed diameter of a circle (104 osu pixel). That is -after- position transforming.
/// </summary>
private const double ALMOST_DIAMETER = 90;
internal OsuHitObject BaseHitObject;
internal double[] Strains = { 1, 1 };
internal int MaxCombo = 1;
private Vector2 normalizedStartPosition;
private Vector2 normalizedEndPosition;
private float lazySliderLength;
internal OsuHitObjectDifficulty(OsuHitObject baseHitObject)
{
BaseHitObject = baseHitObject;
float circleRadius = baseHitObject.Scale * 64;
Slider slider = BaseHitObject as Slider;
if (slider != null)
MaxCombo += slider.Ticks.Count();
// We will scale everything by this factor, so we can assume a uniform CircleSize among beatmaps.
float scalingFactor = (52.0f / circleRadius);
if (circleRadius < 30)
{
float smallCircleBonus = Math.Min(30.0f - circleRadius, 5.0f) / 50.0f;
scalingFactor *= 1.0f + smallCircleBonus;
}
normalizedStartPosition = BaseHitObject.StackedPosition * scalingFactor;
lazySliderLength = 0;
// Calculate approximation of lazy movement on the slider
if (slider != null)
{
float sliderFollowCircleRadius = circleRadius * 3; // Not sure if this is correct, but here we do not need 100% exact values. This comes pretty darn close in my tests.
// For simplifying this step we use actual osu! coordinates and simply scale the length, that we obtain by the ScalingFactor later
Vector2 cursorPos = baseHitObject.StackedPosition;
Action<Vector2> addSliderVertex = delegate (Vector2 pos)
{
Vector2 difference = pos - cursorPos;
float distance = difference.Length;
// Did we move away too far?
if (distance > sliderFollowCircleRadius)
{
// Yep, we need to move the cursor
difference.Normalize(); // Obtain the direction of difference. We do no longer need the actual difference
distance -= sliderFollowCircleRadius;
cursorPos += difference * distance; // We move the cursor just as far as needed to stay in the follow circle
lazySliderLength += distance;
}
};
// Actual computation of the first lazy curve
foreach (var tick in slider.Ticks)
addSliderVertex(tick.StackedPosition);
addSliderVertex(baseHitObject.StackedEndPosition);
lazySliderLength *= scalingFactor;
normalizedEndPosition = cursorPos * scalingFactor;
}
// We have a normal HitCircle or a spinner
else
normalizedEndPosition = normalizedStartPosition;
}
internal void CalculateStrains(OsuHitObjectDifficulty previousHitObject, double timeRate)
{
calculateSpecificStrain(previousHitObject, OsuDifficultyCalculator.DifficultyType.Speed, timeRate);
calculateSpecificStrain(previousHitObject, OsuDifficultyCalculator.DifficultyType.Aim, timeRate);
}
// Caution: The subjective values are strong with this one
private static double spacingWeight(double distance, OsuDifficultyCalculator.DifficultyType type)
{
switch (type)
{
case OsuDifficultyCalculator.DifficultyType.Speed:
if (distance > SINGLE_SPACING_TRESHOLD)
return 2.5;
else if (distance > STREAM_SPACING_TRESHOLD)
return 1.6 + 0.9 * (distance - STREAM_SPACING_TRESHOLD) / (SINGLE_SPACING_TRESHOLD - STREAM_SPACING_TRESHOLD);
else if (distance > ALMOST_DIAMETER)
return 1.2 + 0.4 * (distance - ALMOST_DIAMETER) / (STREAM_SPACING_TRESHOLD - ALMOST_DIAMETER);
else if (distance > ALMOST_DIAMETER / 2)
return 0.95 + 0.25 * (distance - (ALMOST_DIAMETER / 2)) / (ALMOST_DIAMETER / 2);
else
return 0.95;
case OsuDifficultyCalculator.DifficultyType.Aim:
return Math.Pow(distance, 0.99);
}
Debug.Assert(false, "Invalid osu difficulty hit object type.");
return 0;
}
private void calculateSpecificStrain(OsuHitObjectDifficulty previousHitObject, OsuDifficultyCalculator.DifficultyType type, double timeRate)
{
double addition = 0;
double timeElapsed = (BaseHitObject.StartTime - previousHitObject.BaseHitObject.StartTime) / timeRate;
double decay = Math.Pow(DECAY_BASE[(int)type], timeElapsed / 1000);
if (BaseHitObject.Type == HitObjectType.Spinner)
{
// Do nothing for spinners
}
else if (BaseHitObject.Type == HitObjectType.Slider)
{
switch (type)
{
case OsuDifficultyCalculator.DifficultyType.Speed:
// For speed strain we treat the whole slider as a single spacing entity, since "Speed" is about how hard it is to click buttons fast.
// The spacing weight exists to differentiate between being able to easily alternate or having to single.
addition =
spacingWeight(previousHitObject.lazySliderLength +
DistanceTo(previousHitObject), type) *
SPACING_WEIGHT_SCALING[(int)type];
break;
case OsuDifficultyCalculator.DifficultyType.Aim:
// For Aim strain we treat each slider segment and the jump after the end of the slider as separate jumps, since movement-wise there is no difference
// to multiple jumps.
addition =
(
spacingWeight(previousHitObject.lazySliderLength, type) +
spacingWeight(DistanceTo(previousHitObject), type)
) *
SPACING_WEIGHT_SCALING[(int)type];
break;
}
}
else if (BaseHitObject.Type == HitObjectType.Circle)
{
addition = spacingWeight(DistanceTo(previousHitObject), type) * SPACING_WEIGHT_SCALING[(int)type];
}
// Scale addition by the time, that elapsed. Filter out HitObjects that are too close to be played anyway to avoid crazy values by division through close to zero.
// You will never find maps that require this amongst ranked maps.
addition /= Math.Max(timeElapsed, 50);
Strains[(int)type] = previousHitObject.Strains[(int)type] * decay + addition;
}
internal double DistanceTo(OsuHitObjectDifficulty other)
{
// Scale the distance by circle size.
return (normalizedStartPosition - other.normalizedEndPosition).Length;
}
}
}