Multidirectional Hillshading algorithm question

[hemantbist]

I recently became aware of this tool. In my very limited tests for mutidirectional-hillshading, this algorithm is performing very well when compared with some other tools.

Is there some paper/study/webpage the describes the underlying idea behind Multidirectional hillshading algorithm used by whitebox-tools? Or some study/tests that compared it some other hillshading algorithms?

1)I searched for listed reference in your manual, but as far as I can tell nothing is mentioned about the hillshading.
Gallant, J. C., and J. P. Wilson, 2000, Primary topographic attributes, in Terrain Analysis: Principles and Applications, edited by J. P. Wilson and J. C. Gallant pp. 51-86, John Wiley, Hoboken, N.J.

2. The Hillshade function and the unequal weights given to different azimuths suggests that it is an enhancement over this old algorithm. Not sure if I am correct.
   https://pubs.usgs.gov/of/1992/of92-422/of92-422.pdf