> ## Documentation Index
> Fetch the complete documentation index at: https://comfytv.org/llms.txt
> Use this file to discover all available pages before exploring further.
# Roto Mask
> Draw a spline shape on the video and bake it into an animated mask, right on the node.
## What this node does
**Roto Mask** turns a hand-drawn polygon into a matte for your clip. You draw a closed shape (3 or more points) directly on the video preview inside the node; on ▶ Run it rasterizes that shape across the whole clip and outputs a mask video.
The shape lives in the node's `shape_keys` widget as spline data (each vertex carries left/right tangent handles, so a smoothed shape follows Bézier curves rather than straight lines). Editing is browser-side and instant; the actual masking pass runs on ▶ Run (ffmpeg/CPU) and produces a new video.
Input and output are `COMFYTV_VIDEO`. The output is a mask clip (white inside the shape, black outside — or inverted). To hand it to native ComfyUI nodes, insert a **Bridge** (`ComfyTV/Bridge`). See [https://github.com/jtydhr88/ComfyTV/blob/main/docs/bridges.md](https://github.com/jtydhr88/ComfyTV/blob/main/docs/bridges.md).
## When to use it
* Isolate a subject or region that has no clean color to key on
* Create a garbage matte to trim junk out of a keyed edge
* Make a quick shape mask to limit a color grade or blur to one area
## The on-node editor
The card shows the video with a canvas overlay:
* **Click** on empty space to drop a new vertex; the shape closes automatically once you have 3+ points.
* **Drag** a vertex to move it.
* **Double-click** a vertex to delete it.
* A **smooth** toggle controls whether vertices connect with straight edges or Bézier tangents (smoothing derives handles from neighboring points).
* **Clear** wipes the shape.
You must draw a shape with at least 3 points before running, or the node raises "draw a shape (3+ points) on the node first."
## Parameters
### shape\_keys
The drawn spline, stored as JSON `[{t, points:[{x,y,lx,ly,rx,ry}]}]`. You do not type this — it is written by the on-node editor as you draw. Default empty.
### feather
Edge softness in pixels. Range `0`–`200`, default `0`. Higher values blur the mask edge for a gentler transition. Start at `0` for a hard matte; raise to a few pixels to avoid a razor edge on composites.
### invert
Flip the mask so the area *outside* the shape becomes white. Boolean, default off.
## Outputs
| Output | Type | Meaning |
| -------- | --------------- | --------------------------------------------------------------------------------------------------- |
| **mask** | `COMFYTV_VIDEO` | A mask clip matching the source length; white where the shape covers, black elsewhere (or inverted) |
## Tips
* The current shape is placed at time 0 as a single keyframe; the same shape is used for the whole clip. For a mask that follows motion, mask one frame and feed it to **Mask Propagate**.
* Feather is measured in source pixels, so its visual softness scales with output resolution.
## Related nodes
* **Mask Propagate** — carries a first-frame mask across a moving clip
* **Shape Mask** — parametric gradient/geometric masks without hand-drawing
* **Cutout / Erase** — consume a mask to isolate or remove content