Timeline preview

The Timeline at the bottom of the preview drives every effect in the scene under one shared playhead. You can play, pause, step, seek, loop and restart the whole scene, and — the subject of this page — move and rotate effects along the timeline.

Where the controls live

The timeline's controls are split between two places:

• Playback controls, in the panel itself: Play / Pause, Restart, Step Back, Step Forward, and the time readout (elapsed time and frame number).
• Mode toggles, in the panel's title bar, to the right of the Timeline tab, grouped by what they control and separated by dividers: Follow Cursor · Preview Start, Preview End and Loop · Unpause on Drag and Pause on Seek · Record Effect Orientation · Flag Labels. Hover any of them for its name.

Like every dock's title-bar buttons, the mode toggles are shown for the panel that is currently on top, so if the Timeline shares its space with another panel they appear when the Timeline tab is active.

Moving the playhead

Click anywhere on the timeline to jump the preview to that point, or press and drag to scrub through the effect — the scene follows the cursor as you move it. Dragging past either edge of the visible area scrolls the timeline along with you, so you can reach parts of the effect that are off screen without zooming out first.

While you drag, a small yellow label follows your mouse pointer showing exactly where you are, in both seconds and frames — for example 1.234s f74. The same label appears when you click to jump somewhere. It sits just below and to the right of the pointer so the cursor never covers the digits, and it flips to the other side — left, or above — when it would otherwise run off the edge of the panel.

The label is there for the moment you are aiming, so it gets out of the way as soon as you release the button. It also disappears if something else takes the playhead over while you are dragging — playback resuming, the preview looping, or a restart — since at that point it is no longer showing a position you chose.

The playback controls keep their own permanent readout of the current time and frame, which is unaffected by any of this.

Preview Start and Preview End

Two draggable markers let you preview just a slice of the timeline in a loop, instead of always replaying the whole effect from the very beginning.

• Preview End (teal) — a fixed point where the preview loops back. While the effect is playing, the moment the playhead reaches Preview End it jumps back to the start. Turn it on with the Preview End button in the panel's title bar.
• Preview Start (green) — a fixed point the preview begins from. Turn it on with the Preview Start button. Once enabled, it becomes the point the preview rewinds to — the Restart button, the Preview End loop and the automatic "out of particles" loop all return here instead of the effect's beginning.

Each marker shows a vertical line and a labelled flag (Preview Start / Preview End). Drag either the line or the flag to move it. The region outside the previewed slice is dimmed, so you can see at a glance which part of the timeline is being looped.

The two markers keep out of each other's way: Preview Start always stays to the left of Preview End, and neither can move into the effect's pre-warm (pre-simulation) zone. When you first turn a marker on it appears near the edge of the currently visible timeline (Preview Start near the left, Preview End near the right), so it lands where you can see it whatever your zoom.

Pre-warm still runs. Even when Preview Start is set to a later time, the effect is still simulated from its true beginning first, so it is fully warmed up when it appears at the Preview Start point — you see the effect exactly as it would look at that moment, not a cold restart.

Both markers are remembered per effect and saved with it, and moving or toggling them can be undone with Undo.

Generator markers

Besides the two preview markers, the timeline shows where each generator of your effect starts and stops emitting. A generator with a start delay or a fixed end time draws a vertical boundary line at each of those points, plus a comb of small ticks marking the individual shots. Every boundary carries a labelled flag — Gen Start or Gen End — so you can tell the boundaries apart when several sit close together. When the scene holds more than one emitter, each flag is prefixed with its emitter's name (for example Smoke: Gen Start), so it is always clear which emitter a boundary belongs to.

Flags are grab handles as well as labels: drag a flag (or its line) to move that boundary, and the generator's delay or end time follows. Because a flag is tied to its own boundary, dragging it always moves that boundary even when another one sits at exactly the same moment. Flags stack into rows when they would overlap, and they flip to the other side of their line near the edges of the window so a label is never cut off.

When several flags land on the same moment and stack up, they are ordered top to bottom to match the order of the emitters in the Emitters list, so the same emitter is always in the same place. Reorder the emitters and the flags follow immediately. The effect-wide markers — Preview Start, Preview End, Pre-sim and Empty Loop — belong to no single emitter and always take the top row.

Full and compact flags

The Flag Labels button in the panel's title bar switches between two ways of labelling flags:

• On (the default) — full captions: Gen Start, Gen End, or Smoke: Gen Start when the scene holds more than one emitter.
• Off — compact: a flag shows a small icon plus its emitter's name, and just the icon when there is a single emitter or the emitter is unnamed. Flags shrink right down, which keeps a busy effect's timeline readable.

Each icon is the one that concept already uses elsewhere in the editor, so a flag stays recognisable without its caption: generator boundaries take the Generation section icon from the Emitter Guide, while Preview Start, Preview End and the Empty Loop marker each take the icon of their own title-bar toggle.

Nothing is lost in compact mode: hover any flag to see its full caption in a tooltip. Tooltips work in both modes. A boundary's Start and End flags stay distinguishable because they sit on opposite sides of their line — Start opens to the right, End closes to the left. The setting applies to every effect and is remembered between sessions.

Hiding markers you don't need

A busy effect can put a lot of boundaries on the timeline at once. Every generator has a Show visualizer setting that controls whether it draws its markers, and there are two ways to reach it:

• From the timeline — right-click the generator's flag and choose Hide visualizer.
• From the block — clear the Show visualizer checkbox in the generator block's properties.

Both do the same thing and both can be undone with Undo. The generator keeps working exactly as before — this only affects what the timeline draws.

The block you currently have selected always shows its markers, whatever this setting says, so you never lose sight of the generator you are editing. That also means hiding the visualizer of the selected block appears to do nothing until you select something else — the setting is applied, it just cannot take effect while the block is being edited.

Switched-off emitters

An emitter you switch off in the Emitters list takes no part in the effect, so its generators stop drawing markers on the timeline too — no boundaries, no flags, and nothing left behind to click on. Switch the emitter back on and its markers return. This keeps the timeline showing only what the effect actually plays.

Preview background color

The preview toolbar has a Background color button — a small color swatch that shows the preview's current background color. Click it to open a color picker; the preview updates live as you adjust the color, and pressing Cancel restores the previous one. The color is remembered per effect — each effect keeps its own background — and is saved with the effect and restored the next time you open it. New effects start with a black background.

Grid placement

The reference grid can sit in three places relative to your particles. Click the small dropdown arrow on the right of the Show Grid toolbar button to choose:

• Grid on background — the grid always draws behind every particle, so nothing in your effect is ever crossed by grid lines.
• Grid by depth — the grid is depth-tested against the particles: parts of the grid in front of a particle show, parts behind it are hidden, just like a real surface in the scene.
• Grid in front — the grid always draws on top, but semi-transparently so it stays readable without hiding your effect. On a dark background it stays as bright as the other modes. This is the default.

The button itself still toggles the grid on and off; only the arrow opens the placement menu. The choice is saved per effect.

This chooser applies in the planar views (Front, Back, Top, Bottom, Left, Right). In a free-orbit camera the grid is always shown by depth, so the other two modes are greyed out in the menu and only "Grid by depth" is selectable — "over everything" only makes sense for a flat, head-on grid.

View and renderer indicators

Two small pills sit in the top corners of the preview, and clicking either one opens a dropdown menu — the ▾ arrow after the text marks them as dropdowns:

• Top-left — renderer pill. Shows which renderer is driving the preview, CPU or GPU, each in its own colour. Click it to switch the renderer for the current effect.
• Top-right — view pill. Shows the current camera view — Free Camera, Orthographic, or a named planar view (Front, Back, Top, Bottom, Left, Right); an asterisk (for example Top*) means you are temporarily orbiting away from a planar view. Click it to jump to any view.

When playback cannot keep up

Some effects are heavier than one frame's worth of time — a very high particle count, an expensive scheme, or a seek that makes the preview rebuild a long run. When that happens the preview cannot show every frame at the effect's real speed, so playback runs slower than real time. The editor tells you about it in two places at once:

• The timeline playhead turns red instead of its usual yellow.
• A red SLOWDOWN pill appears at the top-center of the preview, so you can see it without looking away from the effect.

Even a single slowed frame shows the pill in full: it fades in quickly, stays fully lit for about a second, then fades out. Any further slowdown restarts that cycle. This means you cannot miss a brief hitch — it always shows up as a clear flash rather than a flicker you might never notice — while an effect that is behind continuously simply keeps the pill lit the whole time.

You will also see both indicators briefly while seeking backwards, because the preview has to rebuild the effect's run up to the point you asked for. That is expected and stops as soon as it catches up.

The indicator is about preview performance only — it does not mean anything is wrong with your effect, and it says nothing about how the effect will perform in your game, where it runs through an exported runtime rather than the editor's preview. If it is lit constantly and you want smoother editing, try lowering the effect's particle capacity, or switching the renderer with the top-left pill.

Textures follow your files

The preview watches the texture files your effects use. Edit a texture in an external image editor and save it — the preview picks up the change within a moment, with no editor restart and no project reopen; the effect keeps playing with the new image. This works in both renderers (CPU and GPU). If a texture file goes missing from disk, the preview shows a red-and-white checkerboard placeholder in its place and switches back to the real image as soon as the file reappears.

Particle-count stats

The timeline shows how many particles each effect has alive, in two places.

Population curve and current-frame readout

Each effect draws a filled population curve across the timeline — how many particles it has at every frame, so you can see it fill and fade over time. On top of the curve, a horizontal readout line marks the count at the frame under the playhead, meeting the curve right at the cursor, with a small flag showing the exact number. The line and flag use the effect's own curve colour, so with several effects in the scene you get one line and flag per effect; the flags sit at the right edge and shift left so they never overlap or leave the timeline. The line follows the count under the cursor every frame, while the number on the flag refreshes about once a second during playback (and immediately when you pause, seek or restart) so it stays readable instead of flickering. If the current frame's count is not ready yet, the readout holds the last known value from the previous few frames, and hides while it catches up.

Per-emitter count in the Emitters list

In the Emitters window, each emitter's capacity badge also shows the number of particles that emitter has alive on the current frame, inline as count / capacity — the live count in blue before the grey capacity, on the same line (no extra row). It updates about once a second during playback, and immediately when you seek or restart. The count is the emitter's total across all of its instances (matching how capacity is shown), and it works with both the CPU and GPU preview renderers. When no count is available the badge shows the plain capacity.

Moving an effect

Select an effect in the preview and drag its gizmo (or type into the Position / Rotation fields in the Properties panel, or use the toolbar's Make Zero Position / Make Zero Rotation buttons — all go through the same path). The effect re-simulates live from the new pose and follows the gizmo on screen. What happens to that pose over time depends on one transport toggle.

Record Effect Orientation

Next to Step Forward on the timeline transport is a record-dot toggle, Record Effect Orientation. It has two modes. New effects start with it off (steady mode), and its state is remembered per effect — reopen an effect and it comes back the way you left it.

On — record the motion

While the toggle is on, moving an effect records its pose onto the timeline at the current frame:

• A moving drag records a path; holding still records a single pose.
• Seek or loop back and the effect replays exactly that recorded movement, with the gizmo following along.
• Drag it again on a later pass and the recording is overwritten from that point forward.
• Each effect records independently — moving one never disturbs another.
• The recorded motion is saved with the project and survives close/reopen and undo/redo.

Off — steady position (default)

While the toggle is off, moving an effect instead sets one constant position for it, with no recording:

• The pose you set stays put across seek, restart and loop — it is simply where the effect sits from now on.
• You can move effects while the timeline is playing (the Position / Rotation fields stay editable during playback, not only while paused).
• Moving one effect never disturbs another.

Switching modes

You can flip the toggle at any time, even during playback — the effect keeps running, it does not restart.

• Turning it off (entering steady mode) clears any motion you had recorded, leaving each effect at its base position. This is a single undo step.
• Turning it back on starts recording fresh.

If you move an effect in steady mode and then seek, loop or restart back to before that move, the preview rebuilds the run up to your cursor — a brief "catching up" pause, the same as seeking backwards normally — so the effect shows correctly at its steady position throughout. Seeking or looping to a point after the move behaves like any normal seek.