# .nk import and export

> Opening, importing, exporting and copy-pasting Nuke scripts; Unsupported nodes, Groups and gizmos.

Oink reads and writes Nuke's `.nk` script format. Its own comps are `.oink` files; `.nk` is for exchanging work with Nuke.

## Ways in and out

| Action | What happens |
|---|---|
| *File › Open Nuke Script…* | replaces the comp with the script; the script's frame range, fps and format are applied |
| *File › Import Nuke Script…* | adds the script's nodes to the current comp (names made unique) |
| `./launch_opencomp.sh shot.nk` | opens the script at launch |
| *File › Export Nuke Script…* | writes the whole comp, or only the selected nodes |
| Ctrl+C / Ctrl+V | the clipboard holds real Nuke node text: nodes copied in Nuke paste here, and nodes copied here paste into Nuke |

After an import, a summary lists the Nuke classes that had no equivalent.

## How nodes are translated

- Each Nuke class maps to one node; the full list is the [Nuke node map](/docs/nuke-users/node-map). Knobs with the same name carry over; renamed knobs are translated both ways (each [node page](/docs/nodes) lists them). A .nk knob with no match on the node imports as a knob of the same name, or is kept unchanged so it is written back on export.
- **Unsupported nodes.** A class with no equivalent becomes an [Unsupported](/docs/nodes/unsupported) node: drawn red, all its knobs kept, input 0 passed straight through. On export it is written back exactly as it was read, so a round trip through Oink does not lose it.
- A node's `label` that only repeats its own name (an old automatic label) is dropped on paste and import, so a renamed node does not show two names.
- Knobs we do not use are kept and written back unchanged.
- **Groups** become real Group nodes; Ctrl+Enter opens one, Ctrl+Backspace goes back up. Nested groups work.
- **Gizmos.** A class that matches a `.gizmo` file on the plugin path imports as a Group built from that file, and exports as the gizmo class again (without its children, as Nuke writes it). The plugin path, searched in order: `$OPENCOMP_PLUGIN_PATH`, `~/.opencomp/gizmos`, `$NUKE_PATH`, `~/.nuke` (with sub-folders). Gizmos found there also appear in the Tab menu.
- **User knobs** (`addUserKnob`) on any node are shown on their own tabs in Properties, keep their values and animation, and are written back. Link knobs follow their target.
- **Expressions and Tcl.** Knob expressions (including `parent.`, `input0.` and node-name references) and the Tcl that Nuke scripts use are evaluated. `[python ...]` calls go to the [`nuke` Python module](/docs/nuke-users/python).
- **Several views.** A script with views (for example left and right) keeps them: the views and their colours are read from the Root settings, and a number, colour or checkbox knob with per-view values (`{default left 1 right 2}`) imports with those values. In Properties, *Split off* and *Unsplit* beside a knob make or remove a per-view value. The values are written back to the `.nk`.
- **Precomp.** A Precomp reads its own `.nk` file; its contents are not written into the parent script.
- **Roto and Tracker.** Classic Roto bezier shapes (with feather and animation) and Tracker4 track tables import. Paint strokes and some per-shape attributes do not; the original shape text is kept and written back.
- **BlinkScript** kernels import with their source and parameter values (see [BlinkScript and OFX](/docs/nuke-users/blink-ofx)). **OFX** nodes import when the plugin is installed. Read and Write nodes for movies keep Nuke's `mov64` knob names, so movie settings survive a round trip (see [Movies and web formats](/docs/concepts/movies)).

## Round trips

Import, export and import again gives the same graph. Unsupported nodes, unknown knobs and the original Root settings are carried through, so a script can go Nuke → Oink → Nuke without losing what Oink does not understand.


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Sources: opencomp_core/nk/importer.py, opencomp_core/nk/exporter.py, opencomp_core/nk/mapping.py, opencomp_core/nk/mapping_gap.py, opencomp_core/nk/gizmos.py, opencomp_core/nk/user_knobs.py, opencomp_core/nk/tcl.py, opencomp_core/nk/tcl_eval.py, opencomp_core/nk/roto_nk.py, opencomp_core/nk/tracker4.py, opencomp_electron/src/components/shell/nkActions.ts