How a bake works

A bake works out the simulation for every frame of the scene's frame range, from the first frame to the last, and writes each frame to a file in the cache folder. The particles object then plays those files. Nothing is worked out while you play or render: it's all read from disk.

BakeCopy Anchor Link

Press Bake in the simulation's panel. The button turns into a progress bar ("Frame 42 of 250 · 1 min left") with a stop button, and the status bar shows the same. Blender stays free to use while it runs; you can play the frames already baked.

When it's done, the status box under the button says where the bake stands:

Under the status come the particle count at the end, where the bake ran (the CPU, or which GPU) and how long it took.

Bake part of it, or carry onCopy Anchor Link

The menu beside the Bake button (⌄) has the other ways to bake:

• Bake to Frame N bakes from the start up to the frame you're on, for a quick look at the start.
• Continue to the End carries a bake that stopped short on to the scene's last frame. The frames already baked are kept.
• Re-bake From Frame N keeps the frames up to the last state saved at or before the frame you're on, and bakes on from there with the settings as they are now (N is the frame it starts at). Use it when only the end needs to change: a collider you moved late in the shot, say.
• Bake in Background is a switch: on, bakes run in a separate Blender, so this one stays light. See Background bakes.
• Bake All bakes every simulation in the scene (when there's more than one).
• Free Bake deletes the bake's files.

When there's a quick way on, it's also a button under the status box: Continue, or Re-bake From N.

Carrying on works from state saves: the bake saves the whole simulation every few frames (Save State Every, 10 by default) and always at its last frame. A bake that carries on from a save gives exactly the frames a straight bake would have. See State saves and carrying on.

StopCopy Anchor Link

The stop button beside the progress bar (in the sidebar, or in the status bar) stops the bake after the frame it's on. The frames finished are kept: the status says "Baked to frame N of M", and Continue carries on from there.

What marks a bake oldCopy Anchor Link

A bake remembers everything it read. When any of it changes, the status box says Changed since the bake (in red), the old bake keeps playing, and the next bake picks the change up. Auto Bake bakes again by itself.

A bake is marked old by a change to:

• any setting marked New bake, and anything in the simulation's flow;
• the scene's frame range or frame rate;
• an object the bake reads (the emitter, colliders, the force object, objects named in the flow): moving it, keyframing its motion, or its parent's; editing its mesh; its modifiers or shape keys.

A bake is not marked old by:

• moving to another frame, or playing;
• anything in the Display panel, or a Render Look: these change how the bake looks, live (Live);
• where the bake runs (Compute, the GPU), Auto Bake, the cache folder.

Where a bake goesCopy Anchor Link

Each bake goes in a new numbered folder (bake_0001, bake_0002…) inside a folder for the object, inside a folder for the .blend file. When a new bake finishes, the object plays it and the old folder is removed. A duplicated object plays its original's bake until it bakes its own.

Bake menuFree Bake removes the bake's folder and the object shows nothing. See The cache folder for what the files are and how big they get.

RelatedCopy Anchor Link

• The bake controls: Auto Bake, Draft and every status text.
• Playback and the viewport: how a bake plays.
• Background bakes and Several simulations at once.