Playback and the viewport
How a bake plays: scrubbing, motion between frames and motion blur, the baked range, and keeping the viewport light.
Once baked, a simulation is just files on disk, and the particles object reads the one for the frame you're on. Playing, scrubbing and rendering all work the same way, so they're quick and always agree.
Scrubbing and playing
Drag along the timeline, or press Space. Any frame shows at once, in any order: frame 200 doesn't need frames 1 to 199 first. Blender keeps frames it has read in memory, so playing a second time is quicker still.
Between frames, and motion blur
A bake is saved once a frame, with each particle's velocity and spin. Between two frames (a subframe, or the moments a motion-blurred render samples) each particle moves on along its velocity from the frame before, and keeps turning. So:
- Motion blur works in Cycles and EEVEE, on spheres and on shapes, with streaks the right length, even when particles are born, die or change order.
- Very fast particles that curve or bounce within a frame show a straight path between frames. That's rarely seen at normal speed; in slow motion it can be. See Playback Time.
Only the baked frames show
Outside the frames that were baked (before the first, after the last, or everything when there's no bake) the particles object shows nothing. If a simulation disappears partway through a shot, check the status box: "Baked to frame 120 of 250" means it stopped short; Continue bakes the rest.
A lighter viewport
Big simulations can slow the viewport down. The Display panel has two settings for it; neither needs a new bake:
- Viewport Share shows a share of the particles in the viewport, the same ones every frame. 0.1 shows a tenth. Renders always show them all, and the bake has them all.
- Sphere Radius sets the size of the spheres the particles show as (unless they bump into each other, or are rigid bodies: then their size is part of the simulation, and changing it needs a new bake).
Show particles as your own models with the Display panel's Shapes collection: each particle shows as one of its objects, turned and scaled with it. They're picked at random, or in a flow by a Shape operator.
Reopening and moving the project
The particles object finds its bake by a path relative to the .blend file
(//vecflow_cache/...), so the file plays its bake again after you reopen it,
and after you move or copy the whole project folder, the cache folder with
it. To render on another computer, even one without VecFlow, use Collect
for Render in Bake Settings:
it saves a copy of the file with its bakes beside it, in one folder.
Playing at another speed
The Playback Time section of the Display panel plays the bake ahead or behind (Offset) and faster, slower, held or backwards (Speed). Both can be keyframed, for a ramp into slow motion, and neither needs a new bake. The liquid's surface, smoke and meshes made by the bake follow.