# HydraRender

> Renders the 3D scene through a USD Hydra render delegate.

Renders the 3D scene through a USD Hydra render delegate. Storm (real-time, in the backend) by default; Karma CPU/XPU when Houdini is installed (runs husk); Cycles (hdCycles) runs in the backend on the standalone engine when the Hydra build is installed. Same inputs as ScanlineRender: bg sets the format, obj/scn, cam. Output: rgba (scene-linear, unclamped), depth (1/Z or Z), optional N. Karma also renders progressively in the Viewer.

| Node | HydraRender |
|---|---|
| Menu | 3D › HydraRender |
| **Names in each format** | |
| .oink comp (JSON) | `"type": "OC_N_hydrarender"` |
| .nk script | none: written as an Oink node |
| Python | `nuke.createNode("OC_N_hydrarender")` |
| Assistant (MCP) | `create_node(type="HydraRender")` |
| Tab search | `hydrarender`, or its initials `hr` |

![HydraRender properties](/shots/nodes/hydrarender@2x.webp)

## Inputs and outputs

| Port | Name | Type |
|---|---|---|
| input 0 | bg | image |
| input 1 | obj/scn | scene |
| input 2 | cam | scene |
| output 0 | Image | image |

## Knobs

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

| Knob | Label | Type | Default | Range / values | .nk knob | Description |
|---|---|---|---|---|---|---|
| `delegate` | delegate | menu | `storm` | storm (Storm), karma (Karma CPU), karma_xpu (Karma XPU), cycles (Cycles (hdCycles)) |  |  |
| `samples` | samples | float | `4` | 1 to 4096 (integer) |  | Storm: jittered passes averaged; Karma: path-traced samples |
| `lighting_enable_mode` | lighting | menu | `auto` | auto, on, off |  |  |
| `ambient` | ambient | float | `0` | 0 to 1 |  |  |
| `output_depth` | depth | bool | `true` |  |  |  |
| `one_over_z` | 1/Z depth | bool | `true` |  |  |  |
| `output_normal` | normal (N) | bool | `false` |  |  |  |

### 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 |  |  |  |  |


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Sources: opencomp_core/nodes/three_d/hydra_render.py, opencomp_electron/src/components/properties/knobSchema.ts, opencomp_core/nodes/help/hydrarender.md