function multiplyScalarAndAdd(out, a, b, scale) {
  out[0] = a[0] + b[0] * scale;
  out[1] = a[1] + b[1] * scale;
  out[2] = a[2] + b[2] * scale;
  out[3] = a[3] + b[3] * scale;
  out[4] = a[4] + b[4] * scale;
  out[5] = a[5] + b[5] * scale;
  out[6] = a[6] + b[6] * scale;
  out[7] = a[7] + b[7] * scale;
  out[8] = a[8] + b[8] * scale;
  out[9] = a[9] + b[9] * scale;
  out[10] = a[10] + b[10] * scale;
  out[11] = a[11] + b[11] * scale;
  out[12] = a[12] + b[12] * scale;
  out[13] = a[13] + b[13] * scale;
  out[14] = a[14] + b[14] * scale;
  out[15] = a[15] + b[15] * scale;
  return out;
}
Adds two mat4's after multiplying each element of the second operand by a scalar value.

@param {mat4} out the receiving vector
@param {mat4} a the first operand
@param {mat4} b the second operand
@param {Number} scale the amount to scale b's elements by before adding
@returns {mat4} out