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Roto Mask

Roto Mask · screenshot coming soon

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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.

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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

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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.”

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Parameters

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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.

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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.

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invert

Flip the mask so the area outside the shape becomes white. Boolean, default off.

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Outputs

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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.
  • 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