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Make curve approximators implement common interface

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smoogipoo 2018-10-04 16:13:18 +09:00
parent bd915e8dca
commit b3e105ba93
5 changed files with 96 additions and 89 deletions
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125
osu.Game/Rulesets/Objects/BezierApproximator.cs
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@ -1,29 +1,77 @@
// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
using System;
using System.Collections.Generic;
using OpenTK;
namespace osu.Game.Rulesets.Objects
{
public readonly ref struct BezierApproximator
public class BezierApproximator : IApproximator
{
private readonly int count;
private readonly ReadOnlySpan<Vector2> controlPoints;
private readonly Vector2[] subdivisionBuffer1;
private readonly Vector2[] subdivisionBuffer2;
private const float tolerance = 0.25f;
private const float tolerance_sq = tolerance * tolerance;
public BezierApproximator(ReadOnlySpan<Vector2> controlPoints)
{
this.controlPoints = controlPoints;
count = controlPoints.Length;
private int count;
private Vector2[] subdivisionBuffer1;
private Vector2[] subdivisionBuffer2;
/// <summary>
/// Creates a piecewise-linear approximation of a bezier curve, by adaptively repeatedly subdividing
/// the control points until their approximation error vanishes below a given threshold.
/// </summary>
/// <returns>A list of vectors representing the piecewise-linear approximation.</returns>
public List<Vector2> Approximate(List<Vector2> controlPoints)
{
count = controlPoints.Count;
subdivisionBuffer1 = new Vector2[count];
subdivisionBuffer2 = new Vector2[count * 2 - 1];
List<Vector2> output = new List<Vector2>();
if (count == 0)
return output;
Stack<Vector2[]> toFlatten = new Stack<Vector2[]>();
Stack<Vector2[]> freeBuffers = new Stack<Vector2[]>();
// "toFlatten" contains all the curves which are not yet approximated well enough.
// We use a stack to emulate recursion without the risk of running into a stack overflow.
// (More specifically, we iteratively and adaptively refine our curve with a
// <a href="https://en.wikipedia.org/wiki/Depth-first_search">Depth-first search</a>
// over the tree resulting from the subdivisions we make.)
toFlatten.Push(controlPoints.ToArray());
Vector2[] leftChild = subdivisionBuffer2;
while (toFlatten.Count > 0)
{
Vector2[] parent = toFlatten.Pop();
if (isFlatEnough(parent))
{
// If the control points we currently operate on are sufficiently "flat", we use
// an extension to De Casteljau's algorithm to obtain a piecewise-linear approximation
// of the bezier curve represented by our control points, consisting of the same amount
// of points as there are control points.
approximate(parent, output);
freeBuffers.Push(parent);
continue;
}
// If we do not yet have a sufficiently "flat" (in other words, detailed) approximation we keep
// subdividing the curve we are currently operating on.
Vector2[] rightChild = freeBuffers.Count > 0 ? freeBuffers.Pop() : new Vector2[count];
subdivide(parent, leftChild, rightChild);
// We re-use the buffer of the parent for one of the children, so that we save one allocation per iteration.
for (int i = 0; i < count; ++i)
parent[i] = leftChild[i];
toFlatten.Push(rightChild);
toFlatten.Push(parent);
}
output.Add(controlPoints[count - 1]);
return output;
}
/// <summary>
@ -92,60 +140,5 @@ namespace osu.Game.Rulesets.Objects
output.Add(p);
}
}
/// <summary>
/// Creates a piecewise-linear approximation of a bezier curve, by adaptively repeatedly subdividing
/// the control points until their approximation error vanishes below a given threshold.
/// </summary>
/// <returns>A list of vectors representing the piecewise-linear approximation.</returns>
public List<Vector2> CreateBezier()
{
List<Vector2> output = new List<Vector2>();
if (count == 0)
return output;
Stack<Vector2[]> toFlatten = new Stack<Vector2[]>();
Stack<Vector2[]> freeBuffers = new Stack<Vector2[]>();
// "toFlatten" contains all the curves which are not yet approximated well enough.
// We use a stack to emulate recursion without the risk of running into a stack overflow.
// (More specifically, we iteratively and adaptively refine our curve with a
// <a href="https://en.wikipedia.org/wiki/Depth-first_search">Depth-first search</a>
// over the tree resulting from the subdivisions we make.)
toFlatten.Push(controlPoints.ToArray());
Vector2[] leftChild = subdivisionBuffer2;
while (toFlatten.Count > 0)
{
Vector2[] parent = toFlatten.Pop();
if (isFlatEnough(parent))
{
// If the control points we currently operate on are sufficiently "flat", we use
// an extension to De Casteljau's algorithm to obtain a piecewise-linear approximation
// of the bezier curve represented by our control points, consisting of the same amount
// of points as there are control points.
approximate(parent, output);
freeBuffers.Push(parent);
continue;
}
// If we do not yet have a sufficiently "flat" (in other words, detailed) approximation we keep
// subdividing the curve we are currently operating on.
Vector2[] rightChild = freeBuffers.Count > 0 ? freeBuffers.Pop() : new Vector2[count];
subdivide(parent, leftChild, rightChild);
// We re-use the buffer of the parent for one of the children, so that we save one allocation per iteration.
for (int i = 0; i < count; ++i)
parent[i] = leftChild[i];
toFlatten.Push(rightChild);
toFlatten.Push(parent);
}
output.Add(controlPoints[count - 1]);
return output;
}
}
}

20
osu.Game/Rulesets/Objects/CatmullApproximator.cs
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@ -1,40 +1,32 @@
// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
using System;
using System.Collections.Generic;
using OpenTK;
namespace osu.Game.Rulesets.Objects
{
public readonly ref struct CatmullApproximator
public class CatmullApproximator : IApproximator
{
/// <summary>
/// The amount of pieces to calculate for each controlpoint quadruplet.
/// </summary>
private const int detail = 50;
private readonly ReadOnlySpan<Vector2> controlPoints;
public CatmullApproximator(ReadOnlySpan<Vector2> controlPoints)
{
this.controlPoints = controlPoints;
}
/// <summary>
/// Creates a piecewise-linear approximation of a Catmull-Rom spline.
/// </summary>
/// <returns>A list of vectors representing the piecewise-linear approximation.</returns>
public List<Vector2> CreateCatmull()
public List<Vector2> Approximate(List<Vector2> controlPoints)
{
var result = new List<Vector2>((controlPoints.Length - 1) * detail * 2);
var result = new List<Vector2>();
for (int i = 0; i < controlPoints.Length - 1; i++)
for (int i = 0; i < controlPoints.Count - 1; i++)
{
var v1 = i > 0 ? controlPoints[i - 1] : controlPoints[i];
var v2 = controlPoints[i];
var v3 = i < controlPoints.Length - 1 ? controlPoints[i + 1] : v2 + v2 - v1;
var v4 = i < controlPoints.Length - 2 ? controlPoints[i + 2] : v3 + v3 - v2;
var v3 = i < controlPoints.Count - 1 ? controlPoints[i + 1] : v2 + v2 - v1;
var v4 = i < controlPoints.Count - 2 ? controlPoints[i + 2] : v3 + v3 - v2;
for (int c = 0; c < detail; c++)
{

14
osu.Game/Rulesets/Objects/CircularArcApproximator.cs
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@ -8,23 +8,19 @@ using OpenTK;
namespace osu.Game.Rulesets.Objects
{
public readonly ref struct CircularArcApproximator
public class CircularArcApproximator : IApproximator
{
private const float tolerance = 0.1f;
private readonly ReadOnlySpan<Vector2> controlPoints;
public CircularArcApproximator(ReadOnlySpan<Vector2> controlPoints)
{
this.controlPoints = controlPoints;
}
/// <summary>
/// Creates a piecewise-linear approximation of a circular arc curve.
/// </summary>
/// <returns>A list of vectors representing the piecewise-linear approximation.</returns>
public List<Vector2> CreateArc()
public List<Vector2> Approximate(List<Vector2> controlPoints)
{
if (controlPoints.Count != 3)
throw new ArgumentException("Must have 3 control points to perform circular arc approximation.", nameof(controlPoints));
Vector2 a = controlPoints[0];
Vector2 b = controlPoints[1];
Vector2 c = controlPoints[2];

13
osu.Game/Rulesets/Objects/IApproximator.cs Normal file
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@ -0,0 +1,13 @@
// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
using System.Collections.Generic;
using OpenTK;
namespace osu.Game.Rulesets.Objects
{
public interface IApproximator
{
List<Vector2> Approximate(List<Vector2> controlPoints);
}
}

13
osu.Game/Rulesets/Objects/LinearApproximator.cs Normal file
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@ -0,0 +1,13 @@
// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
using System.Collections.Generic;
using OpenTK;
namespace osu.Game.Rulesets.Objects
{
public class LinearApproximator : IApproximator
{
public List<Vector2> Approximate(List<Vector2> controlpoints) => controlpoints;
}
}