I'm adding photon mapping to my current raytracer to add indirect lighting.
Can someone explain how the radiance estimate works in simple terms and with some simple math? I have read a lot of documents about it online, but the math is beyond my understanding so far. I have used Lambertian and Phong shading in my raytracer, so I'm thinking of using that. Next, how do you add up the power of nearby photons at a point? I see a lot of papers that say you have to divide by the number of photons shot, but doesn't that reduce the power of a photon by way too much? (say divide it by a million photons...)
TLDR: Explain how radiance estimate works in detail but with simple math.