@fimbul-works/vec/dist/esm/2d/rotate-2d.js

A comprehensive TypeScript vector math library providing 2D, 3D, and 4D vector operations with a focus on performance and type safety.

/**
 * Rotates a 2D point around an arbitrary axis point
 * @param {ArrayVector2D} xy - Point to rotate
 * @param {number} phi - Rotation angle in radians
 * @param {ArrayVector2D} axis - Rotation axis point (default: `[0, 0]`)
 * @returns {ArrayVector2D} The rotated vector
 */
export const rotate2D = (xy, phi, axis = [0, 0]) => {
    const cos = Math.cos(phi);
    const sin = Math.sin(phi);
    // No need to translate if axis is [0, 0]
    if (axis[0] === 0 && axis[1] === 0) {
        return [xy[0] * cos - xy[1] * sin, xy[0] * sin + xy[1] * cos];
    }
    // Translate point to origin (relative to axis)
    const translatedX = xy[0] - axis[0];
    const translatedY = xy[1] - axis[1];
    // Rotate around origin
    const rotatedX = translatedX * cos - translatedY * sin;
    const rotatedY = translatedX * sin + translatedY * cos;
    // Translate back
    return [rotatedX + axis[0], rotatedY + axis[1]];
};