[Math][JavaScript][CoffeeScript] 2点を通る直線と円の交点を求める

gistfile1.coffee

#直線の座標A、直線の座標、円の中心点の座標、円の半径
getPointsOfIntersectionWithLineAndCircle=(aX,aY,bX,bY,cX,cY,r)->

	a = bY - aY
	b = aX - bX
	c = -( a*aX + b*aY )

	l = Math.sqrt((bX-aX)*(bX-aX)+(bY-aY)*(bY-aY))

	eX = (bX - aX) / l
	eY = (bY - aY) / l

	vX = -eY
	vY = eX

	k = - (a*cX + b*cY + c)/(a*vX+b*vY)

	pX = cX + k*vX
	pY = cY + k*vY

	if r<k
		return false
	else
		S = Math.sqrt( r*r - k*k )

		x1 = pX + S*eX
		y1 = pY + S*eY
		x2 = pX - S*eX
		y2 = pY - S*eY

		return [x1,y1,x2,y2]