  High Energy Physics processes, such as hard scattering, parton shower, and
hadronization, occur at colliders around the world, e.g., the Large Hadron
Collider in Europe. The various steps are also components within corresponding
Monte-Carlo simulations. They are usually considered to occur in an instant and
displayed in MC simulations as intricate paths hard-coded with the HepMC
format. We recently developed a framework to convert HEP event records into
online 3D animations, aiming for visual Monte-Carlo studies and science
popularization, where the most difficult parts are about designing an event
timeline and particles' movement. As a by-product, we propose here an
event-time-frame format for animation data exchanging and persistence, which is
potentially helpful in other visualization works. The code is maintained at
https://github.com/lyazj/hepani, and the web service is available at
https://ppnp.pku.edu.cn/hepani/index.html.
