gistfile1.cs

    /// <summary>
    /// Structure that represents a rotation in three dimensions.
    /// </summary>
    public struct Quaternion
    {
        const int PACK_COEFF_YZ = 1 << 20;
        const int PACK_COEFF_X  = 1 << 21;

        /// <summary>
        /// The X component of the quaternion.
        /// </summary>
        public readonly double X;
        /// <summary>
        /// The Y component of the quaternion.
        /// </summary>
        public readonly double Y;
        /// <summary>
        /// The Z component of the quaternion.
        /// </summary>
        public readonly double Z;
        /// <summary>
        /// The W component of the quaternion.
        /// </summary>
        public readonly double W;

        /// <summary>
        /// Initializes a new instance of the Quaternion structure.
        /// </summary>
        /// <param name="x">
        /// Type: System.Single
        /// Value of the new Quaternion's X coordinate.
        /// </param>
        /// <param name="y">        
        /// Type: System.Single
        /// Value of the new Quaternion's Y coordinate.
        /// </param>
        /// <param name="z">
        /// Type: System.Single
        /// Value of the new Quaternion's Z coordinate.
        /// </param>
        /// <param name="w">
        /// Type: System.Single
        /// Value of the new Quaternion's W coordinate.
        /// </param>
        public Quaternion(float x, float y, float z, float w)
        {
            X = x;
            Y = y;
            Z = z;
            W = w;
        }

        /// <summary>
        /// Initializes a new instance of the Quaternion structure.
        /// </summary>
        /// <param name="packedQuaternion">
        /// Type: System.UInt64
        /// Value of the packed quarterion
        /// </param>
        public Quaternion(ulong packedQuaternion)
        {
            X = (double)(packedQuaternion >> 42)       / (double)PACK_COEFF_X;
            Y = (double)(packedQuaternion << 22 >> 43) / (double)PACK_COEFF_YZ;
            Z = (double)(packedQuaternion << 43 >> 43) / (double)PACK_COEFF_YZ;
            W = 1 - (X * X + Y * Y + Z * Z);
            if (W < 0) W = Math.Sqrt(W);
        }


        /// <summary>
        ///  Converts the quaternion values of this instance to its equivalent ulong value.
        /// </summary>
        public ulong ToUInt64()
        {
            byte w_sign = (byte)(this.W >= 0 ? 1 : -1);

            ulong x = (ulong)((this.X * PACK_COEFF_X ) * w_sign) & ((1 << 22) - 1);
            ulong y = (ulong)((this.Y * PACK_COEFF_YZ) * w_sign) & ((1 << 21) - 1);
            ulong z = (ulong)((this.Z * PACK_COEFF_YZ) * w_sign) & ((1 << 21) - 1);

            return (z | (y << 21) | (x << 42));
        }

        /// <summary>
        ///  Converts the numeric values of this instance to its equivalent string representations, separator is space.
        /// </summary>
        public override string ToString()
        {
            return string.Format(CultureInfo.InvariantCulture, "(X:{0} Y:{1} Z:{2} W:{3})", this.X, this.Y, this.Z, this.W);
        }
    }