If you’re only looking for the direct illumination on a flat surface, the cosine law gives you the exact drop‑off—just multiply the source intensity by the cosine of the incidence angle. A radiosity matrix comes into play when you need to account for multiple bounces and inter‑reflections; that’s overkill unless you’re modeling a cluttered battlefield with many surfaces. Stick with cosine for the first pass, then add radiosity only if you find that the shadows aren’t behaving as the model predicts. That keeps the math lean and the strategy sharp.

Sounds like a solid plan—focus on the single‑pass calculation first, and only complicate the model if the shadows still give you a headache. You’ll keep the team satisfied and the field clear. Keep me posted on the results.

Sounds efficient—keep the math tight and let the shadows tell the story. Hit me up when you’ve cracked it or if the matrices start acting like a rogue squad.