State saves and carrying on
How a bake saves the whole simulation every few frames, so it can carry on from the middle with the same result.
A bake saves the whole simulation (every particle, the gas, the bodies and joints, the random numbers) every few frames, and always at its last frame. From one of these state saves, a bake can carry on from the middle instead of starting over.
What carries on from a save
- Continue (or Continue to the End in the Bake menu) carries a bake that stopped short on to the scene's last frame, from the save at its last frame. The frames already baked are kept.
- Re-bake From N keeps the frames before N and bakes from N with the settings as they are now. N is the frame after the newest save before the frame you're on.
A bake that carries on from a save gives exactly the frames a straight bake from the start would have, to the bit, with the same settings. So stopping and continuing never shows a seam.
Re-bake From is for changes that only matter later in the shot: a collider you moved at frame 180, say. Frames before N keep what they had, so a change that should have shown earlier won't, until you bake from the start.
How often
Save State Every in Bake Settings: every 10 frames by default. More often gives finer places to re-bake from, and takes more disk:
- a save is about the size of a frame of the cache;
- with smoke, several frames' worth, since the gas is saved in full.
The last frame is always saved, whatever the setting, so a stopped bake can always continue.
Where they are
Saves are files named state_0010.bin and so on, in the bake's folder beside
its frames. A new bake hard-links the frames it keeps from the old one rather
than copying them, so carrying on costs no extra disk for those.
Collect for Render leaves the
saves out: they're only for carrying on.
No saves with NVIDIA Flow
A simulation whose smoke runs on NVIDIA Flow makes no state saves, so it can't continue or re-bake from a frame: it bakes from the start each time. The VecFlow solver has no such limit.