wmelton · November 24, 2017 23:53
diff --git a/Circles-Intersect.js b/Circles-Intersect.js
 //Two circles intersect if, and only if, the distance between their centers is between the sum and the difference of their radii. Given two circles (x0,y0,R0) and (x1,y1,R1), the formula is as follows:

 ABS(R0-R1) <= SQRT((x0-x1)^2+(y0-y1)^2) <= (R0+R1)
 //Squaring both sides lets you avoid the slow SQRT, and stay with ints if your inputs are integer:

 (R0-R1)^2 <= (x0-x1)^2+(y0-y1)^2 <= (R0+R1)^2
 //Since you need only a yes/no test, this check is faster than calculating the exact intersection points.

 //Edit: corrected for the "one circle inside the other" case.
	//Two circles intersect if, and only if, the distance between their centers is between the sum and the difference of their radii. Given two circles (x0,y0,R0) and (x1,y1,R1), the formula is as follows:

	ABS(R0-R1) <= SQRT((x0-x1)^2+(y0-y1)^2) <= (R0+R1)
	//Squaring both sides lets you avoid the slow SQRT, and stay with ints if your inputs are integer:

	(R0-R1)^2 <= (x0-x1)^2+(y0-y1)^2 <= (R0+R1)^2
	//Since you need only a yes/no test, this check is faster than calculating the exact intersection points.

	//Edit: corrected for the "one circle inside the other" case.