Caustic map with photon map data incorporated into importance sampling for multi-bounce MC GI // note the improved indirect lighting on glossy sphere and better resolution of lighting beneath glass sphere // 8 bounce, 4 spp, ...

Caustic map with Multi-bounce MC GI reference image // 8 bounce, 4 spp, ...

Final Gathering + Caustics map // sorry I forget the parameters : // the area below the glass sphere looks a touch dark - perhaps I should be adding the photon map at the shading point as well as in the FG... - I think thats double counting though

Photon mapping direct and indirect lighting // 1e7 photons, 0.05 Roulette extinction chance, 128 max per estimate, radius 1.5, 0.6 ellipticity // 8 bounces, 64 SPP, 1280x720, 195.6s, i5-12600K 16 threads - photon mapping single threaded

Photon mapping for indirect lighting // 1e7 photons, 0.25 Roulette extinction chance, 512 max per estimate, radius 1.5, 0.33 ellipticity // 8 bounces, 8 to 64 SPP - avg 10 SPP, 16 SPL, 1280x720, 129.45s, i5-12600K 16 threads - photon mapping single threaded

Direct lighting only reference

Direct lighting using photon mapping // 1e7 photons // Irradiance estimate: 128 max, linear filter, 0.25 radius, 0.2 ellipticity // 0 bounces, 8 SPP, 1280x720, 9.315s, i5-12600K 16 threads