/// <summary>
/// Creates a list of CubicBezierKnots automatically generating control points so the path is C1 and C2 continous,
/// (meaning the tangent and acceleration at the knots in the path are the same). This method uses the
/// Kochanek-Bartels algorithm.
/// </summary>
/// <returns>The a list of bezier knots.</returns>
/// <param name="looped">If set to <c>true</c> the curve will be looped.</param>
/// <param name="points">The positions os the knots, in order.</param>
/// <param name="tension">
/// A tension of 0 indicates smooth corners. A tension of 1 indicates sharp corners. Values larger than
/// this range can cause the curves to overshoot. Values smaller than 0 will cause the curves to fold into
/// themselves.
/// </param>
/// <summary>
/// Bias affects how automatic control points should be generated. For a given knot, a positive bias means there
/// will be a strong bend at the start of the outgoing segment, and a negative bias means there will be a strong
/// bend at the end of the incomming segment. The default bias of 0 gives a neutral weighting.
/// </summary>
/// <summary>
/// Continuity affects how automatic control points should be generated. If this value is 0, control points will
/// be C1 continious, (no instant changes in velocity, unless tension is >= 1). This can be though to change how
/// sharp the shape is.
/// </summary>
/// <param name="relativeControlPoints">
/// Should control points be calculated as offsets from the knot position, or as absolute values in the path's
/// coordinate system.
/// </param>
public static List <CubicBezierKnot> GeneratePathKnots(bool looped, IEnumerable <Vector3> points,
float tension = 0f, float bias = 0f, float continuity = 0f, bool relativeControlPoints = false)
{
Vector3[] pointsArray = points.ToArray();
List <CubicBezierKnot> knots = new List <CubicBezierKnot>();
// Special case, for if the path is one point or less.
if (pointsArray.Length < 2)
{
foreach (var point in points)
{
var knot = new CubicBezierKnot();
knot.InControlPoint = point;
knot.OutControlPoint = point;
knot.Position = point;
knot.Type = CubicBezierKnotType.Singular;
}
return(knots);
}
for (int i = 0; i < pointsArray.Length; ++i)
{
int prevIndex = i - 1;
// Wrap the prevIndex around if the path is looped. Otherwise clamp it to zero.
if (prevIndex < 0)
{
prevIndex = looped ? prevIndex + pointsArray.Length : 0;
}
// Wrap the nextIndex around if the path is looped. Otherwise clamp it.
int nextIndex = looped ? (i + 1) % pointsArray.Length : Mathf.Min(i + 1, pointsArray.Length - 1);
Vector3 prevPoint = pointsArray[prevIndex];
Vector3 currentPoint = pointsArray[i % pointsArray.Length];
Vector3 nextPoint = pointsArray[nextIndex];
// Explanation of how we generate the midpoints can be found here:
// https://en.wikipedia.org/wiki/Kochanek%E2%80%93Bartels_spline
var inControlPoint = -(
0.5f * (1f - tension) * (1f + bias) * (1f - continuity) * (currentPoint - prevPoint) +
0.5f * (1f - tension) * (1f - bias) * (1f + continuity) * (nextPoint - currentPoint));
var outControlPoint =
0.5f * (1f - tension) * (1f + bias) * (1f + continuity) * (currentPoint - prevPoint) +
0.5f * (1f - tension) * (1f - bias) * (1f - continuity) * (nextPoint - currentPoint);
if (!relativeControlPoints)
{
inControlPoint += currentPoint;
outControlPoint += currentPoint;
}
var knot = new CubicBezierKnot();
knot.Position = currentPoint;
knot.InControlPoint = inControlPoint;
knot.OutControlPoint = outControlPoint;
knot.Type = CubicBezierKnotType.Continuous;
knots.Add(knot);
}
return(knots);
}
/// <summary>
/// Creates an automatic bezier path between the given list of points. If tension, bias and continuity are all 0,
/// This path will be a catmull-rom spline.
/// </summary>
/// <param name="tension">
/// A tension of 0 indicates smooth corners. A tension of 1 indicates sharp corners. Values larger than
/// this range can cause the curves to overshoot. Values smaller than 0 will cause the curves to fold into
/// themselves.
/// </param>
/// <summary>
/// Bias affects how automatic control points should be generated. For a given knot, a positive bias means there
/// will be a strong bend at the start of the outgoing segment, and a negative bias means there will be a strong
/// bend at the end of the incomming segment. The default bias of 0 gives a neutral weighting.
/// </summary>
/// <summary>
/// Continuity affects how automatic control points should be generated. If this value is 0, control points will
/// be C1 continious, (no instant changes in velocity, unless tension is >= 1). This can be though to change how
/// sharp the shape is.
/// </summary>
/// <param name="looped">
/// Whether the path should be looped or not.
/// </param>
/// <param name="overshootMode">
/// How path overshooting should be handled.
/// </param>
/// <param name="points">The points the bezier should map through.</param>
public AutoBezierPath(float tension, float bias, float continuity, bool looped, PathOvershootMode overshootMode,
IEnumerable <Vector3> points)
{
List <CubicBezierKnot> knots = CubicBezierKnotUtils.GeneratePathKnots(looped, points, tension, bias, continuity);
var paths = new List <IPath>();
int numberOfPoints = points.Count();
int count = looped ? numberOfPoints : numberOfPoints - 1;
for (int i = 0; i < count; ++i)
{
int index = i;
int nextIndex = (i + 1) % numberOfPoints;
CubicBezierKnot firstKnot = knots[index];
CubicBezierKnot nextKnot = knots[nextIndex];
var path = new NormalizedBezierPath(firstKnot.Position, firstKnot.OutControlPoint, nextKnot.InControlPoint,
nextKnot.Position);
paths.Add(path);
}
_path = new ChainedPath(overshootMode, paths);
}
/// <summary>
/// Takes an existing knot, and forces it's control points to be recalculated based on the CubicBezierKnotType.
/// </summary>
/// <param name="knot">The knot to recalculate.</param>
/// <param name="inControlFixed">
/// If set to <c>true</c>, the in control point will be considered fixed and the out control point will be
/// recalculated. Otherwise the out control point will be considered fixed and the int control point will be
/// recalculated.
/// </param>
/// <param name="relativeControlPoints">
/// Should control points be calculated as offsets from the knot position, or as absolute values in the path's
/// coordinate system.
/// </param>
public static void RecalculateControlPoint(this CubicBezierKnot knot, bool inControlFixed = true,
bool relativeControlPoints = false)
{
Vector3 fixedControlPoint = inControlFixed ? knot.InControlPoint : knot.OutControlPoint;
Vector3 freeControlPoint = inControlFixed ? knot.OutControlPoint : knot.InControlPoint;
if (!relativeControlPoints)
{
fixedControlPoint -= knot.Position;
freeControlPoint -= knot.Position;
}
switch (knot.Type)
{
case CubicBezierKnotType.Continuous:
freeControlPoint = -fixedControlPoint;
break;
case CubicBezierKnotType.Aligned:
Vector3 tangent = -fixedControlPoint.normalized;
float magnitude = freeControlPoint.magnitude;
freeControlPoint = tangent * magnitude;
break;
case CubicBezierKnotType.Singular:
fixedControlPoint = Vector3.zero;
freeControlPoint = Vector3.zero;
break;
}
if (!relativeControlPoints)
{
fixedControlPoint += knot.Position;
freeControlPoint += knot.Position;
}
knot.InControlPoint = inControlFixed ? fixedControlPoint : freeControlPoint;
knot.OutControlPoint = inControlFixed ? freeControlPoint : fixedControlPoint;
}
/// <summary>
/// Gets the path of a segment. A segment is any curve connecting two knots in the path.
/// </summary>
/// <returns>The path segment.</returns>
/// <param name="segmentIndex">
/// The index of the path segment. Must be less than NumberOfSegments.
/// </param>
public IPath GetSegmentPath(int segmentIndex)
{
Assert.IsTrue((Looped && segmentIndex <= _knots.Count) || (!Looped && segmentIndex < _knots.Count));
int nextIndex = (segmentIndex + 1) % _knots.Count;
CubicBezierKnot firstPoint = _knots[segmentIndex];
CubicBezierKnot secondPoint = _knots[nextIndex];
var startPoint = firstPoint.Position;
var startControlPoint = firstPoint.OutControlPoint + firstPoint.Position;
var endControlPoint = secondPoint.InControlPoint + secondPoint.Position;
var endPoint = secondPoint.Position;
if (Normalized)
{
return(new NormalizedBezierPath(startPoint, startControlPoint, endControlPoint, endPoint));
}
else
{
return(new BezierPath(startPoint, startControlPoint, endControlPoint, endPoint));
}
}