gl-vec3/rotateX.js

gl-matrix's vec3, split into smaller pieces

module.exports = rotateX;

/**
 * Rotate a 3D vector around the x-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 rotateX(out, a, b, c){
    var by = b[1]
    var bz = b[2]

    // Translate point to the origin
    var py = a[1] - by
    var pz = a[2] - bz

    var sc = Math.sin(c)
    var cc = Math.cos(c)

    // perform rotation and translate to correct position
    out[0] = a[0]
    out[1] = by + py * cc - pz * sc
    out[2] = bz + py * sc + pz * cc

    return out
}