> ## Documentation Index
> Fetch the complete documentation index at: https://comfytv.org/llms.txt
> Use this file to discover all available pages before exploring further.
# Mask Propagate
> Take a mask drawn on one frame and carry it across the whole moving clip.
## What this node does
**Mask Propagate** solves the motion between frames of your video and warps a single reference mask to follow it. You give it a first-frame mask image; on ▶ Run it tracks feature points frame to frame, fits a motion model, and re-projects the mask so it sticks to the moving subject or region — outputting a mask video for the full clip.
It needs two inputs: the source **video** (`COMFYTV_VIDEO`) and a **mask** image (`COMFYTV_IMAGE`) that matches the frame at `t_ref`. If no mask is wired in, it raises "Mask Propagate needs a first-frame mask image." The output is a `COMFYTV_VIDEO` mask. Bridge to native ComfyUI nodes via `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
* You have a clean mask for one frame (from **Split Part**'s SAM output, Roto Mask, etc.) and want it across the whole shot
* Following a rigid or near-rigid subject that translates, scales, rotates, or skews
* Turning a still cutout into a moving matte without rotoscoping every frame
## Parameters
### model
The motion model fitted between frames. Options: `translation`, `similarity`, `perspective`. Default `similarity`. `translation` handles pure sliding; `similarity` adds rotation and scale; `perspective` adds skew/tilt for planar surfaces. Use the simplest model that matches the motion.
### t\_ref
The timestamp (seconds) of the frame your reference mask corresponds to. Range `0`–`3600`, step `0.05`, default `0`. Set this to the time of the frame you masked.
### max\_points
Maximum number of feature points used to solve the motion. Range `4`–`64`, default `24`. More points can be more robust but slower.
### invert
Invert the propagated mask. Boolean, default off.
## Inputs and outputs
| Slot | Type | Meaning |
| -------------- | --------------- | ------------------------------------------------ |
| **video** (in) | `COMFYTV_VIDEO` | The clip to propagate across |
| **mask** (in) | `COMFYTV_IMAGE` | First-frame mask, matching the frame at `t_ref` |
| **mask** (out) | `COMFYTV_VIDEO` | The mask warped to follow motion across the clip |
## Tips
* The reference mask must line up with the frame at `t_ref` — a mismatch makes the propagation drift from the start.
* **Split Part**'s SAM mask output is a natural source for the first-frame mask.
* Propagation assumes a mostly consistent transform; heavy deformation, occlusion, or motion blur can cause slippage.
## Related nodes
* **Split Part** — produces a per-frame SAM mask to seed this node
* **Roto Mask** — draw the first-frame mask by hand
* **Motion Track** — solve motion as transform data (for pinning/compositing)