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Merge pull request #9050 from bdach/bar-line-floating-point

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Eliminate floating point inaccuracies when generating bar lines
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Dean Herbert 2020-05-22 17:03:33 +09:00 committed by GitHub
commit be02638341
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73
osu.Game.Tests/NonVisual/BarLineGeneratorTest.cs Normal file
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@ -0,0 +1,73 @@
// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
using System.Collections.Generic;
using NUnit.Framework;
using osu.Framework.Utils;
using osu.Game.Beatmaps;
using osu.Game.Beatmaps.ControlPoints;
using osu.Game.Beatmaps.Timing;
using osu.Game.Rulesets.Objects;
namespace osu.Game.Tests.NonVisual
{
public class BarLineGeneratorTest
{
[Test]
public void TestRoundingErrorCompensation()
{
// The aim of this test is to make sure bar line generation compensates for floating-point errors.
// The premise of the test is that we have a single timing point that should result in bar lines
// that start at a time point that is a whole number every seventh beat.
// The fact it's every seventh beat is important - it's a number indivisible by 2, which makes
// it susceptible to rounding inaccuracies. In fact this was originally spotted in cases of maps
// that met exactly this criteria.
const int beat_length_numerator = 2000;
const int beat_length_denominator = 7;
const TimeSignatures signature = TimeSignatures.SimpleQuadruple;
var beatmap = new Beatmap
{
HitObjects = new List<HitObject>
{
new HitObject { StartTime = 0 },
new HitObject { StartTime = 120_000 }
},
ControlPointInfo = new ControlPointInfo()
};
beatmap.ControlPointInfo.Add(0, new TimingControlPoint
{
BeatLength = (double)beat_length_numerator / beat_length_denominator,
TimeSignature = signature
});
var barLines = new BarLineGenerator<BarLine>(beatmap).BarLines;
for (int i = 0; i * beat_length_denominator < barLines.Count; i++)
{
var barLine = barLines[i * beat_length_denominator];
var expectedTime = beat_length_numerator * (int)signature * i;
// every seventh bar's start time should be at least greater than the whole number we expect.
// It cannot be less, as that can affect overlapping scroll algorithms
// (the previous timing point might be chosen incorrectly if this is not the case)
Assert.GreaterOrEqual(barLine.StartTime, expectedTime);
// on the other side, make sure we don't stray too far from the expected time either.
Assert.IsTrue(Precision.AlmostEquals(barLine.StartTime, expectedTime));
// check major/minor lines for good measure too
Assert.AreEqual(i % (int)signature == 0, barLine.Major);
}
}
private class BarLine : IBarLine
{
public double StartTime { get; set; }
public bool Major { get; set; }
}
}
}

11
osu.Game/Rulesets/Objects/BarLineGenerator.cs
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@ -1,6 +1,7 @@
// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
using System;
using System.Collections.Generic;
using System.Linq;
using osu.Framework.Utils;
@ -46,6 +47,16 @@ namespace osu.Game.Rulesets.Objects
for (double t = currentTimingPoint.Time; Precision.DefinitelyBigger(endTime, t); t += barLength, currentBeat++)
{
var roundedTime = Math.Round(t, MidpointRounding.AwayFromZero);
// in the case of some bar lengths, rounding errors can cause t to be slightly less than
// the expected whole number value due to floating point inaccuracies.
// if this is the case, apply rounding.
if (Precision.AlmostEquals(t, roundedTime))
{
t = roundedTime;
}
BarLines.Add(new TBarLine
{
StartTime = t,