Animation Timing

Molkit times every animation automatically from what happens in it. A step where one atom slides a little is short; a step with a lot of travel, several bond changes, or a proton transfer takes longer. A state with mechanism arrows stays on screen until its arrows have drawn, plus a pause to read them. You can leave all of this alone, scale the whole animation, or override single transitions.

The preview, the exported animated SVG, the video export, the timing fields and the speed presets all read the same schedule, so the numbers you see in one place are the numbers you get in the others.

How a pair of states is timed

Molkit plays an animation as a series of pairs: state 1 to state 2, state 2 to state 3, and so on. Each pair has three parts, played in order:

Hold A, the time on the first state before anything moves.
The transition, the movement from the first state to the second.
Hold B, the time on the second state after the movement ends.

In the preview timeline you see this the other way round: a state is on screen for the Hold B of the change arriving at it plus the Hold A of the change leaving it, and that total is its Time on screen.

When a bond forms between atoms that carry radical electrons, a 1.4-second rotation beat is added before the transition so the radical electrons can turn to face each other.

Transition length

A transition starts at 700 ms and grows with what it contains:

Travel. The first 40 units of movement are free. Beyond that, time is added at 150 units per second, measured on the atom that moves farthest.
Events. Bonds forming, bonds breaking, a bond order changing, a lone pair turning into a bond (or back), and atoms entering or leaving each count as one kind of event. Every kind beyond the first adds 250 ms.
Staged transfers. A transfer such as a proton moving from one molecule to another needs at least 1.4 seconds.
An ordinary transition never runs longer than 2.2 seconds.

A pair where Molkit detects a reaction pattern or an electron transfer (see Reaction Choreography) uses a fixed 3-second transition instead.

Hold length

How long a state stays on screen depends mostly on whether it has arrows to draw.

A state with no new arrows settles for about 1 second in total: 0.4 s after it arrives and 0.6 s before it leaves.
A state with new arrows holds while they draw. The first arrow starts 150 ms after the state arrives, each arrow takes 800 ms to draw, and the next one starts 350 ms after the previous one. After the last arrow finishes, the state holds another 800 ms for reading before the next transition.
The first state holds for at least 1 second before anything moves. If it has mechanism arrows, they draw first, followed by the reading pause.
The last state holds for 2 seconds (after its arrows finish, if it has any) before the animation ends or loops.
Text annotations in the state or overlapping its frame add 250 ms per word beyond the first two, up to 5 seconds.

Only arrows that are new in a state draw in. An arrow carried over from the previous state is already on screen and does not redraw.

Change the timing for the whole animation

The Speed setting below the preview timeline applies to the whole animation, in the preview and in export. It runs from 0.25× to 4×; at 2× every part takes half as long.

To aim for a total length instead, type it in seconds in Fit to. Molkit picks the speed that gives that length. Each part keeps a short minimum so fades and arrow draws stay visible, so a very short target may not be reachable; the preview then shows the closest length it could reach. The current total appears under the speed as Length, and the same total shows on the animation toolbar.

Change one state or one change

Below the preview, the timeline shows every state and every change between states as a block, sized by how long it lasts. Click a block to jump there and edit it in the panel below the playback buttons. The panel stays on the block you picked while the preview plays, so you can watch the effect of an edit right away.

A state has Time on screen: how long it stays visible, including the time its arrows take to draw. Extra time goes to reading after the arrows finish; a shorter time first takes from the reading pause and only then draws the arrows faster. A state in the middle of the animation needs at least 0.8 seconds, the first and last at least 0.4.
A change has Duration (the movement itself) and Motion: Smooth (slow start and end), Slow finish, Slow start, or Constant speed. Auto uses Smooth.

Empty fields use the automatic value, shown as the placeholder; Auto next to a field clears your value. The numbers you type are the times that play at the current speed. A block with your own timing has a dot in the timeline. Loop this block while tuning replays the selected block over and over while you adjust it. Reset all timing under the speed clears every state and change.

The same settings are in the docked Animation panel in animation mode: click a state’s thumbnail for its Time on screen, or click the duration chip between two thumbnails for that change’s Duration and Motion. Right-clicking the chip, or the buttons at the top of the panel, also offers speed presets for one change: Quick (0.35 times the automatic values), Slow (1.8 times), and Normal (automatic).

Files made before this timeline may use Bounce or Snap motion; they keep it, shown as an older setting, but it is no longer offered for new changes.

Overrides and arrows

If you give a state less time on screen than its arrows need, the arrows are drawn faster so that every one still completes. They are not cut off.

A state’s or change’s timing belongs to the states on either side of it. If you insert or delete a state so that two states are no longer next to each other, that timing is ignored and the new step uses automatic timing; the preview says how many settings are being ignored and offers Clear to remove them. Excluding a state with the eye toggle does not discard the timing around it; it applies again when you include the state.

When captions appear

A caption that is new in a state normally fades in during the change that leads to it, so it is there when the state arrives. To show it only after the state’s arrows have drawn instead, select it in animation mode and set Appears to After the arrows in its properties panel. In a state with no arrows, the caption appears right after the change. The state stays on screen long enough for the fade, and a pointer arrow attached to the caption waits with it.

The setting only matters where the caption is new. A caption carried over from the previous state is already on screen, so the option is greyed out with the reason shown. Duplicating a state does not copy the setting to the duplicate’s captions.