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Pyro Cache and VDB Export

Select VDB channels, retain preview history and bake versioned volume sequences for playback or downstream use.

The Cache tab contains Initial State, Looping, VDB export-channel selection, preview history and disk baking. For polygon or Alembic output, use the standalone Pro Particles Mesher post effect and the central Output tab when you need polygon/Alembic output.

Lists and Nodes

Lists keep Initial State, Looping and VDB baking together in the Cache tab. With Pyro authored in Nodes, standard Export Channels, Preview History, Bake, and Play Cache remain in Project > Cache & Export because they control the scene's baked sequence and playback. Initial State and Looping become optional Pyro Initial State and Pyro Looping stages in the connected Pyro branch. Their node-owned settings determine the active initial or loop configuration; the standard cache location and bake controls remain shared scene controls.

  1. Save the .blend file before using a relative // Cache Folder.
  2. Finish the domain resolution, required simulation channels, sources, forces, Physics settings, and bake range. Settings such as Voxel Size and enabled channels can require a solver restart.
  3. Enable only the Export Channels needed for playback or downstream work. Smoke is sufficient for a density-only result; fire, colored smoke, motion blur, or external processing require their corresponding grids.
  4. Set Cache Folder, File Name, Frame Digits, and the Blender Volume Object name. Enable Versioning when several independent results must coexist.
  5. Bake a short representative range first. Check motion, boundaries, channel content, and memory use before committing to the complete range.
  6. Set Start and End, then choose Bake. Baking resets the live simulation, evaluates every frame in sequence, and writes the selected VDB channels.
  7. When all VDB writes finish successfully, Play Cache is enabled and the final frame is loaded from disk. Scrub the full range to verify the result.

Cache playback bypasses the live solver. Disable Play Cache before evaluating changed simulation settings, or select a different cache version if the change should become a separate bake.

Export Channels

  • Smoke: includes the density grid in VDB output and playback. Keep it enabled for ordinary smoke rendering.
  • Temperature: includes the temperature grid for shading or downstream processing that needs heat.
  • Velocity: includes the velocity grid for motion blur, advection, or downstream volume work.
  • Color: includes the color grid when Color Channel simulation is enabled.
  • Fuel: includes unburned fuel when Fire Channels are enabled.
  • Flame: includes the flame grid when Fire Channels are enabled.

An enabled simulation channel is not automatically written to the VDB. The matching Export Channel must also be enabled. Conversely, Color, Fuel, and Flame export controls are unavailable when the corresponding simulation channel is disabled. Exporting only the required channels saves disk space and reduces export and loading time.

Preview History

Frames controls how many recent VDB preview frames remain available for timeline scrubbing. Use Bake to keep a complete sequence for playback after reopening the project.

Bake to Disk

  • Cache Folder: base folder for the scene's own Pyro cache subfolder. Relative paths beginning with // require a saved .blend file.
  • The cache subfolder contains a visible pro_particles_cache.json file that records which cache files belong to this scene. Keep this file with the cache so playback and clearing can identify those files.
  • File Name: base name for the VDB sequence. A frame number is appended automatically. Leading periods are removed so the VDB files remain visible in file browsers.
  • Frame Digits: number of digits used for frame numbers, for example four digits produce Pyro_0042.vdb.
  • Volume Object: name of the managed Blender Volume object used to display the cache.
  • Versioning: places standard cache files in numbered v1, v2, and later subfolders so separate bakes can share one base folder.
  • Version: active numbered version when Versioning is enabled. Changing it changes which standard sequence is counted and played.
  • Play Cache: appears when VDB files are found and loads the disk cache instead of live simulation. While cache playback is enabled, Pro Particles Studio manages Blender's Lock Interface render option so VDB frame changes remain safe during foreground rendering, then restores the previous setting when cached playback ends.
  • Start / End: frame range to bake.
  • Bake: resets the solver, simulates the configured range in order, and writes VDB frames. Press Esc to cancel a running bake.
  • Clear VDB Cache: asks for confirmation, then removes only standard VDB and effect-map files recorded as belonging to this scene's cache. It does not delete loop sequences, Initial State data, or other files in the selected folder.

Initial States and Loop Sequences

Initial State and Looping have separate controls; Clear VDB Cache keeps both. Configure their ranges and generation controls under Domain, Solver Mode and Initial State. Generating a loop replaces its previous loop data. After successful generation, the scene's frame range matches the final loop range.

Cache Checks and Common Problems

  • No cache files are found: verify the active Cache Folder, File Name, Versioning state, and Version. Playback only appears for the currently resolved standard cache location.
  • A relative path is rejected: save the .blend file so Blender can resolve //, or use an absolute Cache Folder.
  • A cache subfolder is rejected as occupied: the selected Cache Folder may contain other files. Choose a different Cache Folder if this scene's Pyro cache subfolder already contains other data. Baking and clearing leave those files untouched.
  • Changed settings have no visible effect: turn off Play Cache. Disk playback bypasses the solver and continues showing the baked sequence.
  • A fire or color grid is missing: enable the Fire Channels or Color Channel in Physics and enable the corresponding Export Channel before baking again.
  • The bake starts from an unexpected state: Bake resets the simulation before evaluating the range. Configure Initial State first if the reset should load a saved volume.
  • Only part of a cancelled bake should remain: use Clear VDB Cache before the next production bake so stale standard frames cannot be mixed with the replacement sequence.
  • Bake or loop generation reports a write failure: Play Cache stays disabled. The message identifies a failed VDB path when available. Check disk space and write access, then clear the incomplete sequence before retrying.
  • An export target is invalid or unwritable: Bake and saving an Initial State check write access before starting. If saving a VDB fails, check the reported path and available disk space before baking again.
  • Windows cache paths: folders and filenames may contain accented or other Unicode characters. Long paths work in Blender 5.2 and newer. Blender 5.0 and 5.1 require the complete VDB path, including the scene's cache subfolders and filename, to stay below 260 characters. If the path is rejected, shorten Cache Folder or File Name.