Variance Reduction Optimal Options Method (VROOM). Options are "on" and "off" (default). Needs to be specified if you are calculating radiances and spiky phase functions are present in your atmosphere. If you are using VROOM, please cite: (Buras and Mayer, 2011).
Buras, R., & Mayer, B., (2011), "Efficient unbiased variance reduction techniques for Monte Carlosimulations of radiative transfer in cloudy atmospheres: The solution." J. Quant. Spectrosc. Radiat. Transfer. Vol. 112, pp. 434‒ 447.