d3plus-shape
Version:
Fancy SVG shapes for visualizations
26 lines (25 loc) • 1.19 kB
JavaScript
/**
@function lineIntersection
@desc Finds the intersection point (if there is one) of the lines p1q1 and p2q2.
@param {Array} p1 The first point of the first line segment, which should always be an `[x, y]` formatted Array.
@param {Array} q1 The second point of the first line segment, which should always be an `[x, y]` formatted Array.
@param {Array} p2 The first point of the second line segment, which should always be an `[x, y]` formatted Array.
@param {Array} q2 The second point of the second line segment, which should always be an `[x, y]` formatted Array.
@returns {Boolean}
*/
export default function (p1, q1, p2, q2) {
// allow for some margins due to numerical errors
var eps = 1e-9;
// find the intersection point between the two infinite lines
var dx1 = p1[0] - q1[0],
dx2 = p2[0] - q2[0],
dy1 = p1[1] - q1[1],
dy2 = p2[1] - q2[1];
var denom = dx1 * dy2 - dy1 * dx2;
if (Math.abs(denom) < eps) return null;
var cross1 = p1[0] * q1[1] - p1[1] * q1[0],
cross2 = p2[0] * q2[1] - p2[1] * q2[0];
var px = (cross1 * dx2 - cross2 * dx1) / denom,
py = (cross1 * dy2 - cross2 * dy1) / denom;
return [px, py];
}