code: function subtract(out, a, b) {
    out[0] = a[0] - b[0];
    out[1] = a[1] - b[1];
    out[2] = a[2] - b[2];
    return out;
  }
docs: Subtracts vector b from vector a
  
  @param {vec3} out the receiving vector
  @param {vec3} a the first operand
  @param {vec3} b the second operand
  @returns {vec3} out