# Cryptomatte

> Mattes from Cryptomatte ID layers.

Mattes from Cryptomatte ID layers. Ctrl+click objects in the Viewer (with the panel open) to add them to the Matte List, Ctrl+Shift+click to remove; names come from the manifest in the file. The matte goes to alpha, anti-aliased edges included.

| Node | Cryptomatte |
|---|---|
| Menu | Keyer › Cryptomatte |
| **Names in each format** | |
| .oink comp (JSON) | `"type": "OC_N_cryptomatte"` |
| .nk script | `Cryptomatte` ([how .nk import works](/docs/nuke-users/nk-import)) |
| Python | `nuke.createNode("Cryptomatte")` |
| Assistant (MCP) | `create_node(type="Cryptomatte")` |
| Tab search | `cryptomatte` |

![Cryptomatte properties](/shots/nodes/cryptomatte@2x.webp)

## Usage
- Layer Selection picks which Cryptomatte (object, material, asset) when the file has several.
- The Matte List takes names separated by commas; with Use Wildcards, `flowerA*` picks every match.
- Preview shows each object's ID colour with the picked ones bright; Matte Only shows the matte.

## Inputs and outputs

| Port | Name | Type |
|---|---|---|
| input 0 | Image | image |
| output 0 | Image | image |

## Knobs

Panel tab **Cryptomatte**, in panel order.

| Knob | Label | Type | Default | Range / values | .nk knob | Description |
|---|---|---|---|---|---|---|
| `cryptoLayer` | Layer Selection | text |  |  | `cryptoLayer` | the Cryptomatte layer name (empty = the first one found). |
| `cryptoLayerLock` | Lock Layer Selection | bool | `false` |  | `cryptoLayerLock` |  |
| `keyedName` | Keyed Name | info |  |  | `keyedName` | the last picked name. |
| `matteList` | Matte List | text |  |  | `matteList` | the picked names (`<0.123>` = a raw ID with no manifest entry). |
| `previewEnabled` | Preview | bool | `true` |  | `previewEnabled` |  |
| `matteOnly` | Matte Only | bool | `false` |  | `matteOnly` |  |
| `singleSelection` | Single Selection | bool | `false` |  | `singleSelection` | a pick replaces the list. |
| `useWildcards` | Use Wildcards | bool | `false` |  | `useWildcards` | `*`, `?` and `[]` in names. |
| `matteOutput` | Matte Output | text | `alpha` |  | `matteOutput` | alpha, or another channel such as `matte.a`. |
| `unpremultiply` | Unpremultiply | bool | `false` |  | `unpremultiply` | divide rgb by the matte. |
| `RemoveChannels` | Remove Channels | bool | `false` |  | `RemoveChannels` | drop the Cryptomatte layers from the output. |

### Other knobs (Python, .nk and the assistant; not on the panel)

| Knob | Label | Type | Default | Range / values | .nk knob | Description |
|---|---|---|---|---|---|---|
| `gl_color` | Viewer Controls Color | float ×3 | `0, 0, 0` | 0 to 1 |  |  |
| `postage_stamp_frame` | Static Frame | int | `1` | -2147483648 to 2147483647 |  |  |
| `lifetimeStart` | Lifetime Start | int | `0` | -2147483648 to 2147483647 |  |  |
| `lifetimeEnd` | Lifetime End | int | `100` | -2147483648 to 2147483647 |  |  |
| `useLifetime` | Use Lifetime | boolean | `false` |  |  |  |
| `cached` | Cached | boolean | `false` |  |  |  |
| `bookmark` | Bookmark | boolean | `false` |  |  |  |
| `dope_sheet` | Dope Sheet | boolean | `false` |  |  |  |
| `clone_group` | Clone Group | string |  |  |  |  |
| `link_source` | Link Source | string |  |  |  |  |
| `link_overrides` | Link Overrides | string |  |  |  |  |
| `split_views` | Split Views | string |  |  |  |  |

## Examples

Open these from **Help › Examples…**, or from the **?** menu in this node's Properties panel.

- **Cryptomatte: matte by name** (`examples/cryptomatte/cryptomatte_pick.oink`): Psyop's Cryptomatte sample render (BSD-3-Clause). The Cryptomatte node reads the uCryptoObject ID layers and the manifest in the EXR header; its Matte List holds "bunny", so the alpha is the bunny's coverage (anti-aliased edges included) and the preview shows every object's ID colour with the picked one bright. Open the node and Ctrl+click an object in the Viewer to add it, Ctrl+Shift+click to remove it.


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Sources: opencomp_core/nodes/keyer/cryptomatte.py, opencomp_electron/src/components/properties/knobSchema.ts, opencomp_core/nodes/help/cryptomatte.md, opencomp_core/nk/mapping.py