Playback, caching & determinism

What is cached, what is re-rendered, and why the same frame always gives the same pixels.

The cache

Results are cached per node, per region, per channel set, keyed by a content hash of everything upstream. Change a knob and only what depends on it re-renders. Mark a Cache node where a branch is expensive and settled.

Playback

The playback cache holds decoded frames in RAM (sized from what the machine has). The timeline shows what is resident.

Determinism

The same graph, frame and seed give the same pixels — on this machine, on the farm, next year. Simulations (ParticleSystem3D, the dust and smoke in BS_Disintegrate) are frame-recursive and seeded, so scrubbing to a frame and playing to it give the same answer.