(ded4a3e0a) v0.9.0.7
This commit is contained in:
Joonas Rikkonen
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// MIT License - Copyright (C) The Mono.Xna Team
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// This file is subject to the terms and conditions defined in
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// file 'LICENSE.txt', which is part of this source code package.
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using System;
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using System.ComponentModel;
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using System.Runtime.Serialization;
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namespace Microsoft.Xna.Framework
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{
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/// <summary>
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/// Contains a collection of <see cref="CurveKey"/> points in 2D space and provides methods for evaluating features of the curve they define.
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/// </summary>
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// TODO : [TypeConverter(typeof(ExpandableObjectConverter))]
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[DataContract]
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public class Curve
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{
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#region Private Fields
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private CurveLoopType _preLoop;
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private CurveLoopType _postLoop;
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private CurveKeyCollection _keys;
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#endregion
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#region Public Properties
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/// <summary>
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/// Returns <c>true</c> if this curve is constant (has zero or one points); <c>false</c> otherwise.
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/// </summary>
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[DataMember]
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public bool IsConstant
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{
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get { return this._keys.Count <= 1; }
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}
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/// <summary>
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/// Defines how to handle weighting values that are less than the first control point in the curve.
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/// </summary>
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[DataMember]
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public CurveLoopType PreLoop
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{
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get { return this._preLoop; }
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set { this._preLoop = value; }
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}
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/// <summary>
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/// Defines how to handle weighting values that are greater than the last control point in the curve.
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/// </summary>
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[DataMember]
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public CurveLoopType PostLoop
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{
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get { return this._postLoop; }
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set { this._postLoop = value; }
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}
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/// <summary>
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/// The collection of curve keys.
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/// </summary>
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[DataMember]
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public CurveKeyCollection Keys
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{
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get { return this._keys; }
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}
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#endregion
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#region Public Constructors
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/// <summary>
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/// Constructs a curve.
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/// </summary>
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public Curve()
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{
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this._keys = new CurveKeyCollection();
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}
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#endregion
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#region Public Methods
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/// <summary>
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/// Creates a copy of this curve.
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/// </summary>
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/// <returns>A copy of this curve.</returns>
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public Curve Clone()
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{
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Curve curve = new Curve();
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curve._keys = this._keys.Clone();
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curve._preLoop = this._preLoop;
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curve._postLoop = this._postLoop;
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return curve;
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}
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/// <summary>
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/// Evaluate the value at a position of this <see cref="Curve"/>.
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/// </summary>
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/// <param name="position">The position on this <see cref="Curve"/>.</param>
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/// <returns>Value at the position on this <see cref="Curve"/>.</returns>
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public float Evaluate(float position)
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{
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if (_keys.Count == 0)
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{
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return 0f;
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}
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if (_keys.Count == 1)
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{
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return _keys[0].Value;
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}
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CurveKey first = _keys[0];
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CurveKey last = _keys[_keys.Count - 1];
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if (position < first.Position)
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{
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switch (this.PreLoop)
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{
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case CurveLoopType.Constant:
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//constant
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return first.Value;
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case CurveLoopType.Linear:
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// linear y = a*x +b with a tangeant of last point
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return first.Value - first.TangentIn * (first.Position - position);
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case CurveLoopType.Cycle:
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//start -> end / start -> end
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int cycle = GetNumberOfCycle(position);
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float virtualPos = position - (cycle * (last.Position - first.Position));
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return GetCurvePosition(virtualPos);
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case CurveLoopType.CycleOffset:
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//make the curve continue (with no step) so must up the curve each cycle of delta(value)
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cycle = GetNumberOfCycle(position);
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virtualPos = position - (cycle * (last.Position - first.Position));
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return (GetCurvePosition(virtualPos) + cycle * (last.Value - first.Value));
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case CurveLoopType.Oscillate:
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//go back on curve from end and target start
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// start-> end / end -> start
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cycle = GetNumberOfCycle(position);
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if (0 == cycle % 2f)//if pair
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virtualPos = position - (cycle * (last.Position - first.Position));
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else
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virtualPos = last.Position - position + first.Position + (cycle * (last.Position - first.Position));
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return GetCurvePosition(virtualPos);
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}
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}
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else if (position > last.Position)
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{
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int cycle;
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switch (this.PostLoop)
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{
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case CurveLoopType.Constant:
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//constant
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return last.Value;
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case CurveLoopType.Linear:
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// linear y = a*x +b with a tangeant of last point
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return last.Value + first.TangentOut * (position - last.Position);
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case CurveLoopType.Cycle:
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//start -> end / start -> end
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cycle = GetNumberOfCycle(position);
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float virtualPos = position - (cycle * (last.Position - first.Position));
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return GetCurvePosition(virtualPos);
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case CurveLoopType.CycleOffset:
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//make the curve continue (with no step) so must up the curve each cycle of delta(value)
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cycle = GetNumberOfCycle(position);
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virtualPos = position - (cycle * (last.Position - first.Position));
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return (GetCurvePosition(virtualPos) + cycle * (last.Value - first.Value));
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case CurveLoopType.Oscillate:
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//go back on curve from end and target start
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// start-> end / end -> start
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cycle = GetNumberOfCycle(position);
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virtualPos = position - (cycle * (last.Position - first.Position));
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if (0 == cycle % 2f)//if pair
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virtualPos = position - (cycle * (last.Position - first.Position));
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else
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virtualPos = last.Position - position + first.Position + (cycle * (last.Position - first.Position));
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return GetCurvePosition(virtualPos);
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}
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}
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//in curve
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return GetCurvePosition(position);
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}
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/// <summary>
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/// Computes tangents for all keys in the collection.
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/// </summary>
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/// <param name="tangentType">The tangent type for both in and out.</param>
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public void ComputeTangents (CurveTangent tangentType)
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{
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ComputeTangents(tangentType, tangentType);
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}
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/// <summary>
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/// Computes tangents for all keys in the collection.
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/// </summary>
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/// <param name="tangentInType">The tangent in-type. <see cref="CurveKey.TangentIn"/> for more details.</param>
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/// <param name="tangentOutType">The tangent out-type. <see cref="CurveKey.TangentOut"/> for more details.</param>
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public void ComputeTangents(CurveTangent tangentInType, CurveTangent tangentOutType)
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{
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for (var i = 0; i < Keys.Count; ++i)
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{
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ComputeTangent(i, tangentInType, tangentOutType);
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}
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}
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/// <summary>
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/// Computes tangent for the specific key in the collection.
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/// </summary>
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/// <param name="keyIndex">The index of a key in the collection.</param>
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/// <param name="tangentType">The tangent type for both in and out.</param>
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public void ComputeTangent(int keyIndex, CurveTangent tangentType)
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{
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ComputeTangent(keyIndex, tangentType, tangentType);
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}
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/// <summary>
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/// Computes tangent for the specific key in the collection.
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/// </summary>
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/// <param name="keyIndex">The index of key in the collection.</param>
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/// <param name="tangentInType">The tangent in-type. <see cref="CurveKey.TangentIn"/> for more details.</param>
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/// <param name="tangentOutType">The tangent out-type. <see cref="CurveKey.TangentOut"/> for more details.</param>
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public void ComputeTangent(int keyIndex, CurveTangent tangentInType, CurveTangent tangentOutType)
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{
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// See http://msdn.microsoft.com/en-us/library/microsoft.xna.framework.curvetangent.aspx
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var key = _keys[keyIndex];
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float p0, p, p1;
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p0 = p = p1 = key.Position;
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float v0, v, v1;
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v0 = v = v1 = key.Value;
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if ( keyIndex > 0 )
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{
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p0 = _keys[keyIndex - 1].Position;
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v0 = _keys[keyIndex - 1].Value;
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}
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if (keyIndex < _keys.Count-1)
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{
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p1 = _keys[keyIndex + 1].Position;
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v1 = _keys[keyIndex + 1].Value;
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}
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switch (tangentInType)
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{
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case CurveTangent.Flat:
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key.TangentIn = 0;
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break;
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case CurveTangent.Linear:
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key.TangentIn = v - v0;
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break;
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case CurveTangent.Smooth:
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var pn = p1 - p0;
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if (Math.Abs(pn) < float.Epsilon)
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key.TangentIn = 0;
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else
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key.TangentIn = (v1 - v0) * ((p - p0) / pn);
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break;
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}
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switch (tangentOutType)
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{
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case CurveTangent.Flat:
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key.TangentOut = 0;
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break;
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case CurveTangent.Linear:
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key.TangentOut = v1 - v;
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break;
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case CurveTangent.Smooth:
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var pn = p1 - p0;
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if (Math.Abs(pn) < float.Epsilon)
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key.TangentOut = 0;
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else
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key.TangentOut = (v1 - v0) * ((p1 - p) / pn);
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break;
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}
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}
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#endregion
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#region Private Methods
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private int GetNumberOfCycle(float position)
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{
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float cycle = (position - _keys[0].Position) / (_keys[_keys.Count - 1].Position - _keys[0].Position);
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if (cycle < 0f)
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cycle--;
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return (int)cycle;
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}
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private float GetCurvePosition(float position)
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{
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//only for position in curve
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CurveKey prev = this._keys[0];
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CurveKey next;
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for (int i = 1; i < this._keys.Count; ++i)
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{
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next = this.Keys[i];
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if (next.Position >= position)
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{
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if (prev.Continuity == CurveContinuity.Step)
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{
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if (position >= 1f)
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{
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return next.Value;
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}
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return prev.Value;
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}
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float t = (position - prev.Position) / (next.Position - prev.Position);//to have t in [0,1]
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float ts = t * t;
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float tss = ts * t;
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//After a lot of search on internet I have found all about spline function
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// and bezier (phi'sss ancien) but finaly use hermite curve
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//http://en.wikipedia.org/wiki/Cubic_Hermite_spline
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//P(t) = (2*t^3 - 3t^2 + 1)*P0 + (t^3 - 2t^2 + t)m0 + (-2t^3 + 3t^2)P1 + (t^3-t^2)m1
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//with P0.value = prev.value , m0 = prev.tangentOut, P1= next.value, m1 = next.TangentIn
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return (2 * tss - 3 * ts + 1f) * prev.Value + (tss - 2 * ts + t) * prev.TangentOut + (3 * ts - 2 * tss) * next.Value + (tss - ts) * next.TangentIn;
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}
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prev = next;
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}
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return 0f;
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}
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#endregion
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}
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}
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