The panel's layout is subdivided into four main areas:

Frame range (A)

Use scene range

If checked the number of retimed frames corresponds the number of frames adjusted in the timeline.

First/Last

Used to adjust the first and last retimed frames, e.g. the original sequence has 100 frames, the retimed sequence 200 frames. In this case, enter 0 for “First”, and “200” for “Last”.

Scale velocities and forces

This option recalculates and adjusts all velocities and forces of the retimed sequence.

Interpolate method

Choose which interpolation method you want to use to scale velocities and forces for the retimed frames.

Particles dying at interpolated frames (B)

If you have filtered particles we recommend using an “NBinary Loader” to merge the particles from the “Filter” daemon's “Source Emitters” and “Target Emitter” before using the "Retime Simulation" tool.

Kill at the beginning of the frame

In this case, the currently observed (dying) particle will not exist in any of the interpolated frames.

Kill at the middle of the frame

If this option is active, the observed particle will keep its velocity and move with the fluid until halfway through the interpolated frames, and will then be removed.

Kill at the end of the frame

This method will keep the observed particle's velocity and motion throughout all interpolated frames.

Freeze dying particles

If this option is checked, the dying particles will not be deleted, but they will keep their last positions for all interpolated frames.

When dying particles are not frozen, but killed at the middle or the end of the frame, then they are affected by the “latest” force and keep moving. “Freeze dying particles” cannot be used with the “Kill at the beginning of the frame”.

Timing Example (C)

This is a visual help for evaluating the retimed sequence. The speed of the blue dot, and the length and direction of the green arrow show you whether the retimed simulation is accelerated, decelerated, performing at the same speed, or even running backward. Additionally you will see the ratio between the “Output Frame” (retimed frame) and the simulation's original frame. The minimum and maximum “Output Frames” depend on the “First” and “Last” settings above.

You can also see different colours:

Orange	Frames for some nodes are missing
Red	Frames for all nodes are missing (“Out of bounds”)
Blue	Original frame number
Yellow	Output frame number
Green	Indicates the current velocity when “Scale velocities and forces” is active

Rewind/Play Buttons

“Rewind” resets the timeline to the first frame, “Play” is used to start the preview.

Time function (D)

Time factor

This is a simple multiplier which determines the final length of the retimed simulation. In order to get the correct factor, please use the following formula:

Time factor = Retimed number of frames / Current number of frames
If you prefer see seconds in the timeline example substitute “frames” through “seconds” in the formula above.
Only the retimed values are multiplied with “Time factor”.
The effect is that the retimed sequence becomes longer (> 1.0) or shorter (< 1.0). In other words: you shift the end point of the retimed simulation.

Edit function

A click on this button opens a full-featured curve editor where you can enter → expressions or draw curves. The two axes represent the retimed simulation's time (X axis – horizontal) and the original simulation's time (Y axis – vertical). A complete description with examples and tutorials can be found → here.

Evaluate function as frames instead of seconds

When this option is active, the tool will convert the retiming curve's values into seconds. This makes the curve independent from frame rates.

Let's assume you want to ignore the first 50 frames when retiming a simulation:

By default, the corresponding function is t+50/fps.
The term 50/fps converts frames into seconds, because you cannot add frames and seconds – both values must be either frames or seconds.
At time t = 3.5 s, for example, and fps = 25 f/s, the result is: 3.5 s + 50 f / 25 f/s = 5.5 s

Now, enable this option:

The function is just t+50.
Here, both values are already given as frames and they can be added.
At time t = 87 f, the result is: 87 f + 50 f = 137 f
You will also see that the timeline under “Timing Example” is changing from frames to seconds.

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