Ladybug - Solar Radiation - Theory/Method?

Hi everyone

I am currently using Ladybug to find analyze solar radiation on different facade orientations. As I am going to document this for my project. I’m interested in some knowledge about the methods behind the "Ladybug_Radiation Analysis" component in Ladybug. My first intuition was, that it was using RADIANCE, but then it occured to me that I might not have RADIANCE installed.

Back to the question, is Ladybug using RADIANCE or how does it actually work?

Best regards,

Christian