Files
CypherCore/Framework/GameMath/QuaternionD.cs
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2017-06-19 17:30:18 -04:00

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C#

/*
* Copyright (C) 2012-2017 CypherCore <http://github.com/CypherCore>
* Copyright (C) 2003-2004 Eran Kampf eran@ekampf.com http://www.ekampf.com
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
using System;
using System.Runtime.InteropServices;
using System.Text.RegularExpressions;
namespace Framework.GameMath
{
/// <summary>
/// Represents a double-precision floating-point quaternion.
/// </summary>
/// <remarks>
/// <para>
/// A quaternion can be thought of as a 4-Dimentional vector of form:
/// q = [w, x, y, z] = w + xi + yj +zk.
/// </para>
/// <para>
/// A Quaternion is often written as q = s + V where S represents
/// the scalar part (w component) and V is a 3D vector representing
/// the imaginery coefficients (x,y,z components).
/// </para>
/// <para>
/// Check out http://mathworld.wolfram.com/Quaternion.html for further details.
/// </para>
/// </remarks>
[Serializable]
[StructLayout(LayoutKind.Sequential)]
public struct Quaternion : ICloneable
{
#region Private Fields
private double _w;
private double _x;
private double _y;
private double _z;
#endregion
#region Constructors
/// <summary>
/// Initializes a new instance of the <see cref="Quaternion"/> class with the specified coordinates.
/// </summary>
/// <param name="x">The quaternions's X coordinate.</param>
/// <param name="y">The quaternions's Y coordinate.</param>
/// <param name="z">The quaternions's Z coordinate.</param>
/// /// <param name="w">The quaternions's W coordinate.</param>
public Quaternion(double x, double y, double z, double w)
{
_w = w;
_x = x;
_y = y;
_z = z;
}
/// <summary>
/// Initializes a new instance of the <see cref="Quaternion"/> class using coordinates from a given <see cref="Quaternion"/> instance.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance to copy the coordinates from.</param>
public Quaternion(Quaternion quaternion)
{
_x = quaternion.X;
_y = quaternion.Y;
_z = quaternion.Z;
_w = quaternion.W;
}
public Quaternion(Matrix3 rot) : this(Zero)
{
int[] plus1mod3 = { 1, 2, 0 };
// Find the index of the largest diagonal component
// These ? operations hopefully compile to conditional
// move instructions instead of branches.
int i = (rot[1, 1] > rot[0, 0]) ? 1 : 0;
i = (rot[2, 2] > rot[i, i]) ? 2 : i;
// Find the indices of the other elements
int j = plus1mod3[i];
int k = plus1mod3[j];
// If we attempted to pre-normalize and trusted the matrix to be
// perfectly orthonormal, the result would be:
//
// double c = sqrt((rot[i][i] - (rot[j][j] + rot[k][k])) + 1.0)
// v[i] = -c * 0.5
// v[j] = -(rot[i][j] + rot[j][i]) * 0.5 / c
// v[k] = -(rot[i][k] + rot[k][i]) * 0.5 / c
// w = (rot[j][k] - rot[k][j]) * 0.5 / c
//
// Since we're going to pay the sqrt anyway, we perform a post normalization, which also
// fixes any poorly normalized input. Multiply all elements by 2*c in the above, giving:
// nc2 = -c^2
double nc2 = ((rot[j, j] + rot[k, k]) - rot[i, i]) - 1.0;
this[i] = (float)nc2;
W = (rot[j, k] - rot[k, j]);
this[j] = -(rot[i, j] + rot[j, i]);
this[k] = -(rot[i, k] + rot[k, i]);
// We now have the correct result with the wrong magnitude, so normalize it:
float s = (float)Math.Sqrt(X * X + Y * Y + Z * Z + W * W);
if (s > 0.00001f)
{
s = 1.0f / s;
X *= s;
Y *= s;
Z *= s;
W *= s;
}
else
{
// The quaternion is nearly zero. Make it 0 0 0 1
X = 0.0f;
Y = 0.0f;
Z = 0.0f;
W = 1.0f;
}
}
#endregion
#region Constants
/// <summary>
/// Double-precision floating point zero quaternion.
/// </summary>
public static readonly Quaternion Zero = new Quaternion(0, 0, 0, 0);
/// <summary>
/// Double-precision floating point identity quaternion.
/// </summary>
public static readonly Quaternion Identity = new Quaternion(0, 0, 0, 1);
/// <summary>
/// Double-precision floating point X-Axis quaternion.
/// </summary>
public static readonly Quaternion XAxis = new Quaternion(1, 0, 0, 0);
/// <summary>
/// Double-precision floating point Y-Axis quaternion.
/// </summary>
public static readonly Quaternion YAxis = new Quaternion(0, 1, 0, 0);
/// <summary>
/// Double-precision floating point Z-Axis quaternion.
/// </summary>
public static readonly Quaternion ZAxis = new Quaternion(0, 0, 1, 0);
/// <summary>
/// Double-precision floating point W-Axis quaternion.
/// </summary>
public static readonly Quaternion WAxis = new Quaternion(0, 0, 0, 1);
#endregion
#region Public Properties
/// <summery>
/// Gets or sets the x-coordinate of this quaternion.
/// </summery>
/// <value>The x-coordinate of this quaternion.</value>
public double X
{
get { return _x; }
set { _x = value; }
}
/// <summery>
/// Gets or sets the y-coordinate of this quaternion.
/// </summery>
/// <value>The y-coordinate of this quaternion.</value>
public double Y
{
get { return _y; }
set { _y = value; }
}
/// <summery>
/// Gets or sets the z-coordinate of this quaternion.
/// </summery>
/// <value>The z-coordinate of this quaternion.</value>
public double Z
{
get { return _z; }
set { _z = value; }
}
/// <summery>
/// Gets or sets the w-coordinate of this quaternion.
/// </summery>
/// <value>The w-coordinate of this quaternion.</value>
public double W
{
get { return _w; }
set { _w = value; }
}
/// <summary>
/// Gets the the modulus of the quaternion.
/// </summary>
/// <value>A double-precision floating-point number.</value>
public double Modulus
{
get
{
return System.Math.Sqrt(_w * _w + _x * _x + _y * _y + _z * _z);
}
}
/// <summary>
/// Gets the the squared modulus of the quaternion.
/// </summary>
/// <value>A double-precision floating-point number.</value>
public double ModulusSquared
{
get
{
return (_w * _w + _x * _x + _y * _y + _z * _z);
}
}
/// <summary>
/// Gets or sets the conjugate of the quaternion.
/// </summary>
/// <value>A <see cref="Quaternion"/> instance.</value>
public Quaternion Conjugate
{
get
{
return new Quaternion(-_x, -_y, -_z, _w);
}
set
{
this = value.Conjugate;
}
}
#endregion
#region ICloneable Members
/// <summary>
/// Creates an exact copy of this <see cref="Quaternion"/> object.
/// </summary>
/// <returns>The <see cref="Quaternion"/> object this method creates, cast as an object.</returns>
object ICloneable.Clone()
{
return new Quaternion(this);
}
/// <summary>
/// Creates an exact copy of this <see cref="Quaternion"/> object.
/// </summary>
/// <returns>The <see cref="Quaternion"/> object this method creates.</returns>
public Quaternion Clone()
{
return new Quaternion(this);
}
#endregion
#region Public Static Parse Methods
/// <summary>
/// Converts the specified string to its <see cref="Quaternion"/> equivalent.
/// </summary>
/// <param name="value">A string representation of a <see cref="Quaternion"/></param>
/// <returns>A <see cref="Quaternion"/> that represents the vector specified by the <paramref name="s"/> parameter.</returns>
public static Quaternion Parse(string value)
{
Regex r = new Regex(@"\((?<w>.*),(?<x>.*),(?<y>.*),(?<z>.*)\)", RegexOptions.None);
Match m = r.Match(value);
if (m.Success)
{
return new Quaternion(
double.Parse(m.Result("${x}")),
double.Parse(m.Result("${y}")),
double.Parse(m.Result("${z}")),
double.Parse(m.Result("${w}"))
);
}
else
{
throw new Exception("Unsuccessful Match.");
}
}
/// <summary>
/// Converts the specified string to its <see cref="Quaternion"/> equivalent.
/// A return value indicates whether the conversion succeeded or failed.
/// </summary>
/// <param name="value">A string representation of a <see cref="Quaternion"/>.</param>
/// <param name="result">
/// When this method returns, if the conversion succeeded,
/// contains a <see cref="Quaternion"/> representing the vector specified by <paramref name="value"/>.
/// </param>
/// <returns><see langword="true"/> if value was converted successfully; otherwise, <see langword="false"/>.</returns>
public static bool TryParse(string value, out Quaternion result)
{
Regex r = new Regex(@"\((?<x>.*),(?<y>.*),(?<z>.*),(?<w>.*)\)", RegexOptions.None);
Match m = r.Match(value);
if (m.Success)
{
result = new Quaternion(
double.Parse(m.Result("${x}")),
double.Parse(m.Result("${y}")),
double.Parse(m.Result("${z}")),
double.Parse(m.Result("${w}"))
);
return true;
}
result = Quaternion.Zero;
return false;
}
#endregion
#region Public Static Quaternion Arithmetics
/// <summary>
/// Adds two quaternions.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <returns>A new <see cref="Quaternion"/> instance containing the sum.</returns>
public static Quaternion Add(Quaternion left, Quaternion right)
{
return new Quaternion(left.X + right.X, left.Y + right.Y, left.Z + right.Z, left.W + right.W);
}
/// <summary>
/// Adds two quaternions and put the result in the third quaternion.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <param name="result">A <see cref="Quaternion"/> instance to hold the result.</param>
public static void Add(Quaternion left, Quaternion right, ref Quaternion result)
{
result.X = left.X + right.X;
result.Y = left.Y + right.Y;
result.Z = left.Z + right.Z;
result.W = left.W + right.W;
}
/// <summary>
/// Subtracts a quaternion from a quaternion.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <returns>A new <see cref="Quaternion"/> instance containing the difference.</returns>
public static Quaternion Subtract(Quaternion left, Quaternion right)
{
return new Quaternion(left.X - right.X, left.Y - right.Y, left.Z - right.Z, left.W - right.W);
}
/// <summary>
/// Subtracts a quaternion from a quaternion and puts the result into a third quaternion.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <param name="result">A <see cref="Quaternion"/> instance to hold the result.</param>
public static void Subtract(Quaternion left, Quaternion right, ref Quaternion result)
{
result.X = left.X - right.X;
result.Y = left.Y - right.Y;
result.Z = left.Z - right.Z;
result.W = left.W - right.W;
}
/// <summary>
/// Multiplies quaternion <paramref name="a"/> by quaternion <paramref name="b"/>.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <returns>A new <see cref="Quaternion"/> containing the result.</returns>
public static Quaternion Multiply(Quaternion left, Quaternion right)
{
Quaternion result = new Quaternion();
result.X = left.W * right.X + left.X * right.W + left.Y * right.Z - left.Z * right.Y;
result.Y = left.W * right.Y + left.Y * right.W + left.Z * right.X - left.X * right.Z;
result.Z = left.W * right.Z + left.Z * right.W + left.X * right.Y - left.Y * right.X;
result.W = left.W * right.W - left.X * right.X - left.Y * right.Y - left.Z * right.Z;
return result;
}
/// <summary>
/// Multiplies quaternion <paramref name="a"/> by quaternion <paramref name="b"/> and put the result in a third quaternion.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <param name="result">A <see cref="Quaternion"/> instance to hold the result.</param>
public static void Multiply(Quaternion left, Quaternion right, ref Quaternion result)
{
result.X = left.W * right.X + left.X * right.W + left.Y * right.Z - left.Z * right.Y;
result.Y = left.W * right.Y + left.Y * right.W + left.Z * right.X - left.X * right.Z;
result.Z = left.W * right.Z + left.Z * right.W + left.X * right.Y - left.Y * right.X;
result.W = left.W * right.W - left.X * right.X - left.Y * right.Y - left.Z * right.Z;
}
/// <summary>
/// Multiplies a quaternion by a scalar.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <param name="scalar">A scalar.</param>
/// <returns>A <see cref="Quaternion"/> instance to hold the result.</returns>
public static Quaternion Multiply(Quaternion quaternion, double scalar)
{
Quaternion result = new Quaternion(quaternion);
result.X *= scalar;
result.Y *= scalar;
result.Z *= scalar;
result.W *= scalar;
return result;
}
/// <summary>
/// Multiplies a quaternion by a scalar and put the result in a third quaternion.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <param name="scalar">A scalar.</param>
/// <param name="result">A <see cref="Quaternion"/> instance to hold the result.</param>
public static void Multiply(Quaternion quaternion, double scalar, ref Quaternion result)
{
result.X = quaternion.X * scalar;
result.Y = quaternion.Y * scalar;
result.Z = quaternion.Z * scalar;
result.W = quaternion.W * scalar;
}
/// <summary>
/// Divides a quaternion by a scalar.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <param name="scalar">A scalar.</param>
/// <returns>A <see cref="Quaternion"/> instance to hold the result.</returns>
public static Quaternion Divide(Quaternion quaternion, double scalar)
{
if (scalar == 0)
{
throw new DivideByZeroException("Dividing quaternion by zero");
}
Quaternion result = new Quaternion(quaternion);
result.X /= scalar;
result.Y /= scalar;
result.Z /= scalar;
result.W /= scalar;
return result;
}
/// <summary>
/// Divides a quaternion by a scalar and put the result in a third quaternion.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <param name="scalar">A scalar.</param>
/// <param name="result">A <see cref="Quaternion"/> instance to hold the result.</param>
public static void Divide(Quaternion quaternion, double scalar, ref Quaternion result)
{
if (scalar == 0)
{
throw new DivideByZeroException("Dividing quaternion by zero");
}
result.X = quaternion.X / scalar;
result.Y = quaternion.Y / scalar;
result.Z = quaternion.Z / scalar;
result.W = quaternion.W / scalar;
}
/// <summary>
/// Calculates the dot product of two quaternions.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <returns>The dot product value.</returns>
public static double DotProduct(Quaternion left, Quaternion right)
{
return left.X * right.X + left.Y * right.Y + left.Z * right.Z + left.W * right.W;
}
#endregion
public bool isUnit(double tolerance = 1e-5)
{
return Math.Abs(dot(this) - 1.0f) < tolerance;
}
public Quaternion ToUnit()
{
Quaternion copyOfThis = this;
copyOfThis *= rsq(dot(this));
return copyOfThis;
}
float dot(Quaternion other)
{
return (float)((X * other.X) + (Y * other.Y) + (Z * other.Z) + (W * other.W));
}
float rsq(float x)
{
return 1.0f / (float)Math.Sqrt(x);
}
#region Public Static Complex Special Functions
/// <summary>
/// Calculates the logarithm of a given quaternion.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <returns>The quaternion's logarithm.</returns>
public static Quaternion Log(Quaternion quaternion)
{
Quaternion result = new Quaternion(0, 0, 0, 0);
if (Math.Abs(quaternion.W) < 1.0)
{
double angle = System.Math.Acos(quaternion.W);
double sin = System.Math.Sin(angle);
if (Math.Abs(sin) >= 0)
{
double coeff = angle / sin;
result.X = coeff * quaternion.X;
result.Y = coeff * quaternion.Y;
result.Z = coeff * quaternion.Z;
}
else
{
result.X = quaternion.X;
result.Y = quaternion.Y;
result.Z = quaternion.Z;
}
}
return result;
}
/// <summary>
/// Calculates the exponent of a quaternion.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <returns>The quaternion's exponent.</returns>
public Quaternion Exp(Quaternion quaternion)
{
Quaternion result = new Quaternion(0, 0, 0, 0);
double angle = System.Math.Sqrt(quaternion.X * quaternion.X + quaternion.Y * quaternion.Y + quaternion.Z * quaternion.Z);
double sin = System.Math.Sin(angle);
if (Math.Abs(sin) > 0)
{
double coeff = angle / sin;
result.X = coeff * quaternion.X;
result.Y = coeff * quaternion.Y;
result.Z = coeff * quaternion.Z;
}
else
{
result.X = quaternion.X;
result.Y = quaternion.Y;
result.Z = quaternion.Z;
}
return result;
}
#endregion
#region Public Methods
/// <summary>
/// Inverts the quaternion.
/// </summary>
public void Inverse()
{
double norm = ModulusSquared;
if (norm > 0)
{
double invNorm = 1.0 / norm;
_w *= invNorm;
_x *= -invNorm;
_y *= -invNorm;
_z *= -invNorm;
}
else
{
throw new Exception("Quaternion " + ToString() + " is not invertable");
}
}
/// <summary>
/// Normelizes the quaternion.
/// </summary>
public void Normalize()
{
double norm = Modulus;
if (norm == 0)
{
throw new DivideByZeroException("Trying to normalize a quaternion with modulus of zero.");
}
_w /= norm;
_x /= norm;
_y /= norm;
_z /= norm;
}
/// <summary>
/// Clamps quaternion values to zero using a given tolerance value.
/// </summary>
/// <param name="tolerance">The tolerance to use.</param>
/// <remarks>
/// The quaternion values that are close to zero within the given tolerance are set to zero.
/// </remarks>
public void ClampZero(double tolerance)
{
_x = MathFunctions.Clamp(_x, 0, tolerance);
_y = MathFunctions.Clamp(_y, 0, tolerance);
_z = MathFunctions.Clamp(_z, 0, tolerance);
_w = MathFunctions.Clamp(_w, 0, tolerance);
}
/// <summary>
/// Clamps quaternion values to zero using the default tolerance value.
/// </summary>
/// <remarks>
/// The quaternion values that are close to zero within the given tolerance are set to zero.
/// The tolerance value used is <see cref="MathFunctions.EpsilonD"/>
/// </remarks>
public void ClampZero()
{
_x = MathFunctions.Clamp(_x, 0);
_y = MathFunctions.Clamp(_y, 0);
_z = MathFunctions.Clamp(_z, 0);
_w = MathFunctions.Clamp(_w, 0);
}
#endregion
#region System.Object Overrides
/// <summary>
/// Returns the hashcode for this instance.
/// </summary>
/// <returns>A 32-bit signed integer hash code.</returns>
public override int GetHashCode()
{
return _w.GetHashCode() ^ _x.GetHashCode() ^ _y.GetHashCode() ^ _z.GetHashCode();
}
/// <summary>
/// Returns a value indicating whether this instance is equal to
/// the specified object.
/// </summary>
/// <param name="obj">An object to compare to this instance.</param>
/// <returns><see langword="true"/> if <paramref name="obj"/> is a <see cref="Quaternion"/> and has the same values as this instance; otherwise, <see langword="false"/>.</returns>
public override bool Equals(object obj)
{
if (obj is Quaternion)
{
Quaternion quaternion = (Quaternion)obj;
return (_w == quaternion.W) && (_x == quaternion.X) && (_y == quaternion.Y) && (_z == quaternion.Z);
}
return false;
}
/// <summary>
/// Returns a string representation of this object.
/// </summary>
/// <returns>A string representation of this object.</returns>
public override string ToString()
{
return string.Format("({0}, {1}, {2}, {3})", _w, _x, _y, _z);
}
#endregion
#region Comparison Operators
/// <summary>
/// Tests whether two specified quaternions are equal.
/// </summary>
/// <param name="left">The left-hand quaternion.</param>
/// <param name="right">The right-hand quaternion.</param>
/// <returns><see langword="true"/> if the two quaternions are equal; otherwise, <see langword="false"/>.</returns>
public static bool operator ==(Quaternion left, Quaternion right)
{
return ValueType.Equals(left, right);
}
/// <summary>
/// Tests whether two specified quaternions are not equal.
/// </summary>
/// <param name="left">The left-hand quaternion.</param>
/// <param name="right">The right-hand quaternion.</param>
/// <returns><see langword="true"/> if the two quaternions are not equal; otherwise, <see langword="false"/>.</returns>
public static bool operator !=(Quaternion left, Quaternion right)
{
return !ValueType.Equals(left, right);
}
#endregion
#region Binary Operators
/// <summary>
/// Adds two quaternions.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <returns>A new <see cref="Quaternion"/> instance containing the sum.</returns>
public static Quaternion operator +(Quaternion left, Quaternion right)
{
return Quaternion.Add(left, right);
}
/// <summary>
/// Subtracts a quaternion from a quaternion.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <returns>A new <see cref="Quaternion"/> instance containing the difference.</returns>
public static Quaternion operator -(Quaternion left, Quaternion right)
{
return Quaternion.Subtract(left, right);
}
/// <summary>
/// Multiplies quaternion <paramref name="a"/> by quaternion <paramref name="b"/>.
/// </summary>
/// <param name="left">A <see cref="Quaternion"/> instance.</param>
/// <param name="right">A <see cref="Quaternion"/> instance.</param>
/// <returns>A new <see cref="Quaternion"/> containing the result.</returns>
public static Quaternion operator *(Quaternion left, Quaternion right)
{
return Quaternion.Multiply(left, right);
}
/// <summary>
/// Multiplies a quaternion by a scalar.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <param name="scalar">A scalar.</param>
/// <returns>A <see cref="Quaternion"/> instance to hold the result.</returns>
public static Quaternion operator *(Quaternion quaternion, double scalar)
{
return Quaternion.Multiply(quaternion, scalar);
}
/// <summary>
/// Multiplies a quaternion by a scalar.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <param name="scalar">A scalar.</param>
/// <returns>A <see cref="Quaternion"/> instance to hold the result.</returns>
public static Quaternion operator *(double scalar, Quaternion quaternion)
{
return Quaternion.Multiply(quaternion, scalar);
}
/// <summary>
/// Divides a quaternion by a scalar.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <param name="scalar">A scalar.</param>
/// <returns>A <see cref="Quaternion"/> instance to hold the result.</returns>
public static Quaternion operator /(Quaternion quaternion, double scalar)
{
return Quaternion.Divide(quaternion, scalar);
}
/// <summary>
/// Divides a scalar by a quaternion.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <param name="scalar">A scalar.</param>
/// <returns>A <see cref="Quaternion"/> instance to hold the result.</returns>
public static Quaternion operator /(double scalar, Quaternion quaternion)
{
return Quaternion.Multiply(quaternion, (1.0 / scalar));
}
#endregion
#region Array Indexing Operator
/// <summary>
/// Indexer ( [w, x, y, z] ).
/// </summary>
public double this[int index]
{
get
{
switch (index)
{
case 0:
return _x;
case 1:
return _y;
case 2:
return _z;
case 3:
return _w;
default:
throw new IndexOutOfRangeException();
}
}
set
{
switch (index)
{
case 0:
_x = value;
break;
case 1:
_y = value;
break;
case 2:
_z = value;
break;
case 3:
_w = value;
break;
default:
throw new IndexOutOfRangeException();
}
return;
}
}
#endregion
#region Conversion Operators
/// <summary>
/// Converts the quaternion to an array of double-precision floating point numbers.
/// </summary>
/// <param name="quaternion">A <see cref="Quaternion"/> instance.</param>
/// <returns>An array of double-precision floating point numbers.</returns>
/// <remarks>The array is [w, x, y, z].</remarks>
public static explicit operator double[] (Quaternion quaternion)
{
double[] doubles = new double[4];
doubles[1] = quaternion.X;
doubles[2] = quaternion.Y;
doubles[3] = quaternion.Z;
doubles[0] = quaternion.W;
return doubles;
}
#endregion
}
}