I am sorry to disagree with the answer of Peter Walser. Solving the equations gives on my desk: u = ((bs.y – as.y) * bd.x – (bs.x – as.x) * bd.y) / (bd.x * ad.y – bd.y * ad.x) v = ((bs.y – as.y) * ad.x – (bs.x – as.x) * ad.y) / (bd.x * … Read more
Arash Partow’s FastGEO library contains implementations of many interesting algorithms in computational geometry. Polygon intersection is one of them. It’s written in Pascal, but it’s only implementing math so it’s pretty readable. Note that you will certainly need to preprocess your edges a little, to get them into clockwise or counterclockwise order. ETA: But really, … Read more
It’s possible to check if a point is inside a sector with only integer arithmetic and the basic operations of addition, subtraction and multiplication. For a point to be inside a circular sector, it has to meet the following tests: It has to be positioned counter-clockwise from the start “arm” of the sector. It has … Read more
Here is a Python example which finds the intersection of a line and a plane. Where the plane can be either a point and a normal, or a 4d vector (normal form), In the examples below (code for both is provided). Also note that this function calculates a value representing where the point is on … Read more
For each edge in both polygons, check if it can be used as a separating line. If so, you are done: No intersection. If no separation line was found, you have an intersection. /// Checks if the two polygons are intersecting. bool IsPolygonsIntersecting(Polygon a, Polygon b) { foreach (var polygon in new[] { a, b … Read more
http://www.realtimerendering.com/intersections.html. It’s a huge matrix of algorithms that calculate intersections between various types of objects. Excellent resource.
Or more concisely if set(L) & set(M): # there is an intersection else: # no intersection If you really need True or False bool(set(L) & set(M)) After running some timings, this seems to be a good option to try too m_set=set(M) any(x in m_set for x in L) If the items in M or L … Read more
Use NSMutableSet: NSMutableSet *intersection = [NSMutableSet setWithArray:array1]; [intersection intersectSet:[NSSet setWithArray:array2]]; [intersection intersectSet:[NSSet setWithArray:array3]]; NSArray *array4 = [intersection allObjects]; The only issue with this is that you lose ordering of elements, but I think (in this case) that that’s OK. As has been pointed out in the comments (thanks, Q80!), iOS 5 and OS X 10.7 … Read more
Intersection of Bezier curves is done by the (very cool) Asymptote vector graphics language: look for intersect() here. Although they don’t explain the algorithm they actually use there, except to say that it’s from p. 137 of “The Metafont Book”, it appears that the key to it is two important properties of Bezier curves (which … Read more
Most of the answers already here seem to follow the general idea that: find the intersection of two straight lines passing the given points. determine if the intersection belong to both line segments. But when intersection does not occur often, a better way probably is to reverse these steps: express the straight lines in the … Read more