I’m working on an application, I need to be able to combine two overlapping arbitrary shapes as drawn by the user. This would be a Union operation on the two shapes. The resultant shape would be the silhouette of the two overlapping shapes.
The shapes are stored as a sequence of points in a clockwise manner.
Ideally I’d like an algorithm which will take two arrays of Points (x,y) and return a single array of the resultant shape.
I’ve been reading Wikipedia on Boolean operations on polygons which mentions the Sweep line algorithm but I can’t make the link between this and my goal, alas I’m not a Mathematician.
I’m developing the application in ActionScript 3 but I’m familiar with C#, Java and I can pick my way through C and C++.
Implementing boolean operations correctly is not trivial; fortunately, there are libraries that already implement this functionality.
What language are you using? If it’s C++, take a look at CGAL, the Computational Geometry Algorithms Library.