add = (out, a, b) => {
  out[0] = a[0] + b[0]
  out[1] = a[1] + b[1]
  out[2] = a[2] + b[2]
  return out
}
Adds the coordinates of two vectors (A+B).

@param {vec3} out - receiving vector
@param {vec3} a - first operand
@param {vec3} b - second operand
@returns {vec3} out
@alias module:modeling/maths/vec3.add