Retiming: Basics

The basic usage of “Simulation Retime” is straight-forward, but it is also possible to solve complex tasks with this tool. Everything begins with a simulation – please also create an → OpenGL preview, because it can be used to evaluate the retimed results:

• Create a scene with a standard particle fluid and simulate 50 frames.
• Adjust the viewport's point of view.
• Display shelf > OpenGL Preview
• Please make sure that RealFlow exports preview images under File | RealFlow > Preferences > Preview > Save Image Sequence
• The preview appears in the → “Movie Player”.
• The preview image sequence can be found in the project folder under preview/video/frames.
• Open “Simulation Retime” from Tools shelf > Simulation Retime

Retiming the Simulation

You will see an stylized timeline in the middle of the window:

Stop the "Timing example" with a click on the “Pause” button, and go to the “Frame range” section.

In this example, the simulation should be extended to 100 frames, and therefore the "Frame range" has to be adjusted:

• Disable “Use scene range”
• First > 0
• Last > 100

The next important parameter is “Time factor”: 

• In this example the number of frames will be doubled, but this means that playback speed will be halved, because we want to extend the simulation.
• Time factor > 0.5
• A custom time factor can be calculated with this formula: Time factor = New number of frames / Current number of frames

Previewing the Retimed Simulation

“Simulation Retime” provides two preview methods. The first method is to use the “Timing example” feature:

• Simply click on the play button, and you will see the blue bullet moving.
• With a “Time factor” of 1.0, the progress in time is constant – there aren't any slower or faster periods, and the entire simulation will be played back with exactly the same speed.
• “Output frame” and “Original frame” indicate the relation between retimed and existing frames.

Another, more visual method uses the OpenGL preview you have been creating before:

• Press “Try on Movie Player...” and select a frame from the preview sequence.
• The result appears almost immediately, and you have a realistic preview.

Defining Export Resources

The last step is to do the actual retiming. Switch to the “Input/Output Settings” tab, and check if the emitter's export resources are enabled.

• By default you will see “Particle cache (.bin)”, but if you prefer another type or additional formats just enable the appropriate checkboxes.
• The newly created files will have the prefix or suffix specified under “File prefix” and “File suffix”; by default it is “retimed”.
• We also recommend using a separate folder (“Subfolder”). This way it is possible to create different versions and separate them.
• The complete path and file name is shown as well.

Finally 

• Click on “Retime”.
• The size of the original particle files, and the length of the simulation are the most important factors with regards to retiming speed. The progress is shown in a separate window.