rpg-dialogue-js
Version:
A simple roleplay game dialogue engine and editor.
52 lines (47 loc) • 1.77 kB
text/typescript
/**
* @requires Line
* @requires Vertex
*
* @author Ikaros Kappler
* @date 2020-12-04
* @modified 2020-12-09 Ported from vanilla JS to Typescript.
*/
import { Line } from "../../Line";
import { Vertex } from "../../Vertex";
import { XYCoords } from "../../interfaces";
/**
* Collect all self-intersection points of the given polygon.
*
* If the given polygon (vertices) is not self intersecting then the returned array is empty.
*
* @name findPolygonSelfIntersections
* @param {Array<Vertex>} vertices - The vertices that form the polygon.
* @return Array<Vertex>
*/
export const findPolygonSelfIntersections = ( vertices:Array<XYCoords> ) : Array<Vertex> => {
const pointList : Array<Vertex> = [];
const lineA : Line = new Line( new Vertex(), new Vertex() );
const lineB : Line = new Line( new Vertex(), new Vertex() );
const n : number = vertices.length;
for( var a = 0; a < n; a++ ) {
lineA.a.set( vertices[a] );
lineA.b.set( vertices[(a+1)%n] );
for( var b = 0; b < n; b++ ) {
// Same edge or neighbour edges intersect by definition.
// Skip them.
if( a == b || a+1 == b || a == b+1 || (a==0&&b+1==n) || (b==0&&a+1==n) )
continue;
lineB.a.set( vertices[b] );
lineB.b.set( vertices[(b+1)%n] );
// Commpute the intersection point of the (infinite) lines.
// The point is undefined if and only if both line are parallel (co-linear).
const intersectionPoint : Vertex|undefined = lineA.intersection(lineB);
// Check if the intersection point is on both (finite) edges of the polygon.
if( intersectionPoint
&& lineA.hasPoint(intersectionPoint) && lineB.hasPoint(intersectionPoint) ) {
pointList.push( intersectionPoint );
}
}
}
return pointList;
};