Why Aren't Simulations Saved in the .hip File? Caching in Houdini
If you opened a Houdini scene and the sim is gone, this is why — and how caching to disk actually works.
A common surprise — especially with downloaded scene files: you open the .hip, hit play, and the simulation looks empty or recalculates. That's expected. Here's why.
The .hip stores the recipe, not the result
A Houdini .hip file stores the node network — the instructions to create an effect — not the simulated frames themselves. Simulations are written to cache files on disk (.bgeo.sc, .vdb, .sim, .rs) so the scene file stays small and portable.
If those caches aren't present (or the path doesn't match your machine), the sim simply needs to be re-cached.
How to re-cache
- Open the scene and find the File Cache / ROP node that writes the sim.
- Point its output path somewhere valid on your disk.
- Click Save to Disk and let it cache the frame range.
- Switch the cache to Load — playback is now fast and stable.
This is normal production hygiene, not a bug — it's also why scene files can be shared at all.
Working with downloaded scenes
Every scene file we ship is built this way. The node setups are intact; you re-cache once on your machine and you're working. Our scene files — like the Vellum Cloth Solaris/Redshift scene and the Procedural Metal & Embers scene — include the full setup so a single cache pass gets you a working shot. New to proxies and caching in general? See How to Export & Import Redshift Proxies.
Short version: the .hip is the recipe. Cache it once and it cooks.
Want the actual Houdini files?
Production scene files, HDAs and free video tutorials — built on real shots.