Polygon.isSelfIntersecting doesn't work at all

[sroik]

U need to consider edge points

[iby]

@toineheuvelmans This is caused by point reordering in the init:

Metron/source/Metron/Shape/Polygon.swift

Lines 29 to 53 in 58a6c89

	/// The default initializer, returns a `Polygon` given
	/// the provided array of `CGPoints`. Note that the points
	/// will be rearranged in such a way that certain
	/// calculations can be done more easily.
	/// The initializer asserts on being given at least 3 points.
	public init(points: [CGPoint]) {
	assert(points.count > 2, "A polygon should at least have 3 points.")
	// Store them in "clockwise" direction (sum of edges should be positive)
	var lastPoint = points.last!
	var edgeSum: CGFloat = 0.0
	for point in points {
	let edge = (lastPoint.x - point.x) * (lastPoint.y + point.y)
	edgeSum += edge
	lastPoint = point
	}
	let clockwisePoints = (edgeSum >= 0) ? points : points.reversed()
	// Start at the minXminY point
	let minXminYPoint = clockwisePoints.reduce(clockwisePoints[0], { (($1.x <= $0.x) && ($1.y <= $0.y)) ? $1 : $0 })
	let index = clockwisePoints.index(of: minXminYPoint)!
	let pointsFromIndex = index == 0 ? clockwisePoints : Array((clockwisePoints[index..<clockwisePoints.count] + clockwisePoints[0..<index]))
	self.points = pointsFromIndex
	}

I'm guessing …certain calculations can be done more easily… is about convex hull? Do you remember if there is anything else that relies on this?

[toineheuvelmans]

@sroik It ensures the points and thus line segments are in order. If I recall correctly this is indeed for calculating the convex hull but also for anything that iterates over the points / line segments, so area, lineSegments, isConvex and path.