rpg-dialogue-js
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A simple roleplay game dialogue engine and editor.
72 lines • 2.01 kB
JavaScript
/**
* The Sutherland-Hodgman convex polygon clipping algorithm.
*
* Original version:
* https://rosettacode.org/wiki/Sutherland-Hodgman_polygon_clipping#JavaScript
*
* @author Ikaros Kappler (ported to TypeScript with {x,y} vertices).
* @date 2021-01-29
* @version 1.0.0
*/
/**
* @param {XYCoords}
* @param {XYCoords}
**/
const inside = (cp1, cp2, p) => {
return (cp2.x - cp1.x) * (p.y - cp1.y) > (cp2.y - cp1.y) * (p.x - cp1.x);
};
/**
* @param {XYCoords}
* @param {XYCoords}
* @param {XYCoords}
* @param {XYCoords}
*/
const intersection = (cp1, cp2, s, e) => {
const dc = {
x: cp1.x - cp2.x,
y: cp1.y - cp2.y
};
const dp = {
x: s.x - e.x,
y: s.y - e.y
};
const n1 = cp1.x * cp2.y - cp1.y * cp2.x;
const n2 = s.x * e.y - s.y * e.x;
const n3 = 1.0 / (dc.x * dp.y - dc.y * dp.x);
return { x: (n1 * dp.x - n2 * dc.x) * n3,
y: (n1 * dp.y - n2 * dc.y) * n3
};
};
/**
* @param {Array<XYCoords>} subjectPolygon - Can be any polygon.
* @param {Array<XYCoords>} clipPolygon - Must be convex.
*/
export const sutherlandHodgman = (subjectPolygon, clipPolygon) => {
let cp1 = clipPolygon[clipPolygon.length - 1];
let cp2;
let s;
let e;
let outputList = subjectPolygon;
for (var j in clipPolygon) {
cp2 = clipPolygon[j];
var inputList = outputList;
outputList = [];
s = inputList[inputList.length - 1]; // last on the input list
for (var i in inputList) {
e = inputList[i];
if (inside(cp1, cp2, e)) {
if (!inside(cp1, cp2, s)) {
outputList.push(intersection(cp1, cp2, s, e));
}
outputList.push(e);
}
else if (inside(cp1, cp2, s)) {
outputList.push(intersection(cp1, cp2, s, e));
}
s = e;
}
cp1 = cp2;
}
return outputList;
};
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