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const LINE_PARALLEL_EPSILON = 1e-10;
export function lineEdgeIntersection({
lineX,
lineY,
normalX,
normalY,
x1,
y1,
x2,
y2,
}: {
lineX: number;
lineY: number;
normalX: number;
normalY: number;
x1: number;
y1: number;
x2: number;
y2: number;
}): { x: number; y: number } | null {
const distance1 = halfPlaneSign({
lineX,
lineY,
normalX,
normalY,
x: x1,
y: y1,
});
const distance2 = halfPlaneSign({
lineX,
lineY,
normalX,
normalY,
x: x2,
y: y2,
});
const denom = distance1 - distance2;
if (Math.abs(denom) < LINE_PARALLEL_EPSILON) return null;
const t = distance1 / denom;
if (t < 0 || t > 1) return null;
return {
x: x1 + (x2 - x1) * t,
y: y1 + (y2 - y1) * t,
};
}
export function halfPlaneSign({
lineX,
lineY,
normalX,
normalY,
x,
y,
}: {
lineX: number;
lineY: number;
normalX: number;
normalY: number;
x: number;
y: number;
}): number {
return (x - lineX) * normalX + (y - lineY) * normalY;
}
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