Keyframing settings
Which operator settings keyframes can change through a bake, how a bake follows them, and what happens to the rest.
Many operator settings can change through a bake: keyframe them as you would any setting in Blender, and the bake follows. Ramp a Birth's rate up and down, let Gravity fade, turn up the wind halfway through.
Keyframing a setting
In the flow editor's sidebar, hover over the setting and press I, or right-click it ▸ Insert Keyframe. Go to another frame, change it, and keyframe it again. The keyframes belong to the flow, so every simulation using the flow follows them.
The bake reads each keyframed setting four times a frame and on every key, and goes in a straight line between: each substep uses the value halfway through it. A bake carried on from a state save follows them exactly as a straight one would.
A keyframed Birth Per Frame is counted up as the bake goes, so it makes as many particles as the curve's area, however the frames are split into substeps.
Changing a keyframe marks the bake old, like any change to the flow. Moving an operator up or down the stack keeps its keyframes; removing it removes them.
What can change through a bake
These settings follow their keyframes. On each operator's page they carry the Keyframable badge.
What can't
Settings that change how the flow is put together can't change through a bake: which object, how many, a Liquid's Spacing, a choice such as a Birth's Mode, switches. Keyframes on them are kept as they are at the scene's first frame, and the editor warns:
Blocks: Rigid Body: Density is keyframed, but can't change through a bake: it stays as at frame 1
A Position along a curve keeps its Speed Out and Inherit Motion as at the first frame too.
Drivers and NLA strips aren't followed: a setting driven, or keyframed in an NLA strip, stays as it is when the bake starts, with a warning. To have it followed, keyframe the setting in the flow's own action instead.
Objects can move all they like
This is about operator settings. The objects a flow reads (emitters, colliders, curves, force objects) are followed wherever they go: keyframes, parents, constraints, drivers and modifiers all count. See Moving and deforming emitters and colliders.
The sidebar's settings
A simulation without a flow has its own keyframable settings: they're marked on Sidebar panels. The Playback Time settings of the Display panel are keyframable too, and change how the bake plays without baking again: see Retiming a bake.
Related
How order and mixing matter
The rules of a flow: what order operators go in, what one event can hold, what can't share an event, and what works across events.
Values: data each particle carries
Values are numbers, vectors or yes-or-no flags each particle carries: set them with Set Value, test them with Value Test, weigh operators by them, and read them in shaders.