Source/OpenTK/Math/BezierCurveCubic.cs

#region --- License ---
/* Licensed under the MIT/X11 license.
 * Copyright (c) 2006-2008 the OpenTK Team.
 * This notice may not be removed from any source distribution.
 * See license.txt for licensing detailed licensing details.
 * 
 * Contributions by Georg W�chter.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Text;

namespace OpenTK
{
    [Serializable]
    public struct BezierCurveCubic
    {
        #region Fields

        public Vector2 StartAnchor;

        public Vector2 EndAnchor;

        public Vector2 FirstControlPoint;

        public Vector2 SecondControlPoint;

        public float Parallel;

        #endregion

        #region Constructors

        public BezierCurveCubic(Vector2 startAnchor, Vector2 endAnchor, Vector2 firstControlPoint, Vector2 secondControlPoint)
        {
            this.StartAnchor = startAnchor;
            this.EndAnchor = endAnchor;
            this.FirstControlPoint = firstControlPoint;
            this.SecondControlPoint = secondControlPoint;
            this.Parallel = 0.0f;
        }

        public BezierCurveCubic(float parallel, Vector2 startAnchor, Vector2 endAnchor, Vector2 firstControlPoint, Vector2 secondControlPoint)
        {
            this.Parallel = parallel;
            this.StartAnchor = startAnchor;
            this.EndAnchor = endAnchor;
            this.FirstControlPoint = firstControlPoint;
            this.SecondControlPoint = secondControlPoint;
        }

        #endregion

        #region Functions

        public Vector2 CalculatePoint(float t)
        {
            Vector2 r = new Vector2();
            float c = 1.0f - t;

            r.X = (StartAnchor.X * c * c * c) + (FirstControlPoint.X * 3 * t * c * c) + (SecondControlPoint.X * 3 * t * t * c)
                + EndAnchor.X * t * t * t;
            r.Y = (StartAnchor.Y * c * c * c) + (FirstControlPoint.Y * 3 * t * c * c) + (SecondControlPoint.Y * 3 * t * t * c)
                + EndAnchor.Y * t * t * t;

            if (Parallel == 0.0f)
                return r;

            Vector2 perpendicular = new Vector2();

            if (t == 0.0f)
                perpendicular = FirstControlPoint - StartAnchor;
            else
                perpendicular = r - CalculatePointOfDerivative(t);

            return r + Vector2.Normalize(perpendicular).PerpendicularRight * Parallel;
        }

        private Vector2 CalculatePointOfDerivative(float t)
        {
            Vector2 r = new Vector2();
            float c = 1.0f - t;

            r.X = (c * c * StartAnchor.X) + (2 * t * c * FirstControlPoint.X) + (t * t * SecondControlPoint.X);
            r.Y = (c * c * StartAnchor.Y) + (2 * t * c * FirstControlPoint.Y) + (t * t * SecondControlPoint.Y);

            return r;
        }

        public float CalculateLength(float precision)
        {
            float length = 0.0f;
            Vector2 old = CalculatePoint(0.0f);

            for (float i = precision; i < (1.0f + precision); i += precision)
            {
                Vector2 n = CalculatePoint(i);
                length += (n - old).Length;
                old = n;
            }

            return length;
        }

        #endregion
    }
}

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