particle_census

Counts a particle emitter's live slots on the device. One invocation per slot over the state buffer the update pass writes, applying the same test that pass applies — a slot is alive while age < lifetime — and accumulating into a two-slot u32 counter.

Slot	Counts
0	live particles
1	live particles a dispatch has advanced (age > 0)

The gap between the two is what a state buffer the simulation has not run over looks like: the emitter's spawns wrote slots at age 0, and nothing moved them.

Bindings (see bindings.yaml): particles (read array<f32>), census (read_write array<atomic<u32>>), params (read array<f32>, whose P_MAX_COUNT bounds the pass).

The particle module dispatches it for an emitter that has been asked to confirm its population — sys:requestCensus(), or any sys:observe() — and reads the counter back over the following frames. The answer reaches content through observe().confirmation, carrying the simulated time it was taken at.