Time-series Playback

Kratos writes one file per model-part per time step. Open any file in such a series (legacy .vtk, VTK XML, or .vtm) and the extension detects the naming pattern, groups the sibling files, and loads the whole series as an animation.

Filename grammar

Kratos names files as <prefix>_<rank>_<step>.<ext>. The extension parses this pattern — anchored from the right so part names may contain underscores — infers the parent / child prefix tree, and groups the sibling files in the same directory into a single time-series model. Grouping is per extension: a .vtk and a .vtu series with the same prefix never mix. .stl / .obj / .ply and the extended meshio++ formats always open as static views.

The timeline bar

When multiple time steps are found, a bar appears along the bottom of the viewport:

◀  ▶  ▶▶  ══════●══════════  Step 4  (2/3)  2 fps

• ◀ / ▶▶ — step backward / forward one frame.
• ▶ / ⏸ — play / pause at the configured rate.
• Scrubber — drag to jump to any step instantly.
• fps input — playback speed (1–30 fps).

A single file with no timestep siblings opens as a static preview with no timeline bar.

State is preserved across frames

Camera position, layer visibility, the active field variable, mode, and colormap are all preserved when switching frames — so a field animates cleanly across the series, and toggled layers stay toggled.

SubModelparts across the series

Each submodelpart file in the series (e.g. Main_FixedEdgeNodes_0_*, Main_MovingNodes_0_*) is merged into the frame as an overlay layer by coordinate matching, so the submodelpart tree stays consistent as you scrub.

TIP

The directory is watched for new files, so time steps written while the preview is open automatically extend the timeline — handy for watching a running simulation.