Reference / Effects / Utility
Updated
Roto brush
Roto brush is a Utility effect.
What it does
Section titled “What it does”Turns strokes into a matte and carries it through the shot.
For a tutorial, see Cutting out a subject.
Parameters
Section titled “Parameters”| Parameter | Control | Range | Default | Unit |
|---|---|---|---|---|
| Propagate | Button | - | - | - |
| Cancel | Button | - | - | - |
| Seed from | Dropdown | Strokes · Segment | Strokes | - |
| Matte mode | Dropdown | Matte · Matte inverted | Matte | - |
| View | Dropdown | Result · Matte · Boundary | Result | - |
| Refine radius | Slider | 0 to 64; up to 256 | 8 | - |
| Flow resolution | Dropdown | Native · Half · Quarter | Half | - |
| Flow smoothness | Slider | 0 to 100 | 50 | - |
| Frames | Dropdown | All frames · Layer in to out · Work area | All frames | - |
What each control does
Section titled “What each control does”- Propagate: carries the matte outward from the base frame. Only one propagation runs at a time.
- Cancel: stops the job and keeps the frames already solved; a later Propagate resumes from them.
- Seed from: what the base frame’s matte starts from. On Strokes, the scribbles alone. On Segment, a tap with the Roto brush tool on the base frame is a prompt a segmentation model reads; Alt makes the tap a negative one, and a drag still lays a stroke.
- Matte mode: keep the subject, or drop it.
- View: the cut-out picture, the matte itself, or the picture with the matte’s edge drawn over it.
- Refine radius: how wide the softened band round the matte’s edge is — room for hair, motion blur and smoke. The Refine edge tool paints the band wider where one spot needs more.
- Flow resolution: the resolution the propagation’s motion is measured at. Native is slower and rarely better.
- Flow smoothness: how strongly that motion is regularised.
- Frames: which frames Propagate reaches. All frames is the whole footage however the layer is trimmed, Layer in to out is the frames between the layer’s in and out points, and Work area is the frames inside the composition’s work area. The base frame is always included.
Frames the propagation has not reached render untouched — the effect never holds a neighbouring frame’s matte over them.
Seed from set to Segment asks for a segmentation model, which is an addon installed from Settings ▸ Addons. Without it the propagation is refused and the status line says so.