I found a good picture for visualizing what BSDF is on wikipedia. https://en.wikipedia.org/wiki/Bidirectional_scattering_distribution_function#/media/File:BSDF05_800.png
I found a good picture for visualizing what BSDF is on wikipedia. https://en.wikipedia.org/wiki/Bidirectional_scattering_distribution_function#/media/File:BSDF05_800.png