particle trace

[Xing]

Hello everyone

I have a question about how to create a video to show the trace of particles moving.

The first image is a screen copy of one frame of the full video. Some black spots which in the middle will move in the following frames. I would like to create a new video to keep the moving particles and show the traces. The second image is the desired effect which shows the traces.

Many thanks for any suggestions!

Xing