@technobuddha/library
Version:
A large library of useful functions
35 lines • 3.29 kB
JavaScript
/**
* Calculates the intersection point of two line segments.
* @param a - The first line segment.
* @param b - The second line segment.
* @param extend - If `true`, treats the segments as infinite lines; if `false`, only considers the actual segments.
* @returns The intersection point as a `Point` object if the segments (or lines, if `extend` is `true`) intersect.
* Returns `undefined` if the lines are parallel or coincident.
* Returns `null` if the intersection is outside the segments and `extend` is `false`.
* @example
* ```typescript
* lineIntersection(
* { x0: 0, y0: 0, x1: 4, y1: 4 },
* { x0: 0, y0: 4, x1: 4, y1: 0 }
* ); // { x: 2, y: 2 }
* ```
* @group Geometry
* @category Line Segment
*/
export function lineIntersection(a, b, extend = false) {
const denominator = (b.y1 - b.y0) * (a.x1 - a.x0) - (b.x1 - b.x0) * (a.y1 - a.y0);
if (denominator === 0) {
// Lines are parallel or coincident
return undefined;
}
const ua = ((b.x1 - b.x0) * (a.y0 - b.y0) - (b.y1 - b.y0) * (a.x0 - b.x0)) / denominator;
const ub = ((a.x1 - a.x0) * (a.y0 - b.y0) - (a.y1 - a.y0) * (a.x0 - b.x0)) / denominator;
if (!extend && (ua < 0 || ua > 1 || ub < 0 || ub > 1)) {
return null; // Intersection is outside the line segments
}
return {
x: a.x0 + ua * (a.x1 - a.x0),
y: a.y0 + ua * (a.y1 - a.y0),
};
}
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