Retime Simulation Basics

Owned by thomas (Unlicensed)
Last updated: 17 Aug, 2015
3 min read

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 → SPH standard particle emitter and simulate 50 frames.
  • Adjust the viewport's point of view.
  • Display shelf > OpenGL Preview
  • Please make sure that RealFlow exports preview images under Edit | 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

Now, the simulation should be extended to 100 frames. You can also see a stylized timeline in the middle of the window:

 

 

Please stop it with a click on the “Pause” button, and go to the “Frame range” section. Since we want to create 100 frames, the 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.