两个多边形之间的重叠检查

Question

I have a two polygon shape draw using HTML5 canvas(GWT). I have all the points for two polygon shape. Means I have the list of points for draw this type of polygon.

Below image showing two polygon intersect or overlapping each other. Now I am searching for a solution how to find two polygon "intersect or not" using java? I am using pure java programming without using any third library.

I have another issue. For explaining this issue I am attaching another image below.

This is the another case when one Polygon inside of another Polygon. In this scenario how to calculate minimum distance between two polygon in negative?

Answer 1

Using Postgis Api Using You get Information That Two Polygon intersect or not . Find Following Link As Reference http://www.postgis.net/docs/ST_Intersection.html

Answer 2

You can use the sweepline paradigm.

Consider the horizontal lines passing through the vertexes of either polygons. Two consecutive lines cut out slabs (trapezoids).

As the slabs are simple, convex polygons, checking them for intersection is straightforward: it suffices to detect overlap of the bases (mind the case where they form an X cross).

Now the whole process can be decomposed as

• sorting the vertices of both polygons by increasing ordinates; for every vertex, remember to what polygon it belongs and what are its neighbors with a higher ordinate (none, one or two);

• scanning the vertices by increasing ordinate, while maintaining a list of the edges that are intersected (it is called the active list). Every time you move to another vertex, update the active list;

• testing the slabs for intersection.