Normalized euclidean volume V corresponding to a fixed threshold pulse fluence, as detected by an observer at fixed BH latitude. Black curve: fluence is averaged over successive pulses emitted at random orbital phase with respect to the observer. Red curve: volume corresponding to the peak fluence detected at a given latitude. The cutoff in volume (and fluence) at μ = 0 is an artifact of the finite size of the angular grid used to map outgoing rays. Dotted curve: differential volume V · μ. Left panel: a = 0; right panel: a/M = 0.95.