gl-vec3/rotateZ.js

gl-matrix's vec3, split into smaller pieces

module.exports = rotateZ;

/**
 * Rotate a 3D vector around the z-axis
 * @param {vec3} out The receiving vec3
 * @param {vec3} a The vec3 point to rotate
 * @param {vec3} b The origin of the rotation
 * @param {Number} c The angle of rotation
 * @returns {vec3} out
 */
function rotateZ(out, a, b, c){
    var bx = b[0]
    var by = b[1]

    //Translate point to the origin
    var px = a[0] - bx
    var py = a[1] - by
  
    var sc = Math.sin(c)
    var cc = Math.cos(c)

    // perform rotation and translate to correct position
    out[0] = bx + px * cc - py * sc
    out[1] = by + px * sc + py * cc
    out[2] = a[2]
  
    return out
}