/// <summary>
/// Enumerates the times and places, if any, where a moving line crosses a point during a time step.
/// The line's endpoints move at a constant rate along their linear paths.
/// </summary>
/// <remarks>Original code found here https://github.com/Strilanc/Methods/blob/master/Methods/Methods/LineSweepPoint/GeometryUtil.cs </remarks>
public static IEnumerable<Sweep> WhenLineSweepsPoint(Vector2d point, Line pathOfLineStartPoint, Line pathOfLineEndPoint)
{
var a = point - pathOfLineStartPoint[0];
var b = -pathOfLineStartPoint.Delta;
var c = pathOfLineEndPoint[0] - pathOfLineStartPoint[0];
var d = pathOfLineEndPoint.Delta - pathOfLineStartPoint.Delta;
//return from t in QuadraticRoots(b.Cross(d), a.Cross(d) + b.Cross(c), a.Cross(c))
return from across in QuadraticRoots(Vector2Ext.Cross(b, d), Vector2Ext.Cross(a, d) + Vector2Ext.Cross(b, c), Vector2Ext.Cross(a, c))
where across >= 0 && across <= 1
let start = pathOfLineStartPoint.Lerp(across)
let end = pathOfLineEndPoint.Lerp(across)
let time = point.LerpProjectOnto(new Line(start, end))
where time >= 0 && time <= 1
orderby time
select new Sweep(timeProportion: time, acrossProportion: across);
}
private static void PlaceOnPortal(IPortalCommon instance, IPortal portal, float t)
{
Line portalLine = new Line(Vector2Ext.ToDouble(Portal.GetWorldVerts(portal)));
Transform2d transform = (Transform2d)instance.WorldTransform;
transform.Position = (Vector2d)portalLine.Lerp(t);
instance.WorldTransform = (Transform2)transform;
}
