Roto
Interactive bezier spline rotoscoping. Draw precise mask shapes with curves, rectangles, and ellipses.
You draw directly in the Preview panel, and one Roto node holds as many shapes as you need, each added to or subtracted from the mask. It can also output the masked image itself (see Output). The same editor draws the paths of Path Warp and Scatter’s Path mode, so everything on this page works there too.
Shapes combine in list order, and soft edges blend smoothly: an Add shape fills in where its feathered edge overlaps another, with no crease along the seam, and a Subtract shape removes coverage in proportion to its own, so a half-transparent hole takes away half.
Every shape fills its true outline: each edge pixel is covered by exactly the part of it inside the shape, and a rectangle or ellipse with a fractional position or size lands exactly where its numbers put it. An emboss, glow, outline or bevel built on a Roto circle follows the curve smoothly, with no facets.
The tool row above the Preview holds the tools and the buttons that act on the selection.
| Tool | Key | What it does |
|---|---|---|
| Select | V | Select shapes and points, move them, scale and rotate them, and change feather. Every gesture below. |
| Pen | B | Click to place a corner point, drag to place a smooth point with handles. Click the first point to close the shape; press Enter, Escape or right-click to leave it open. A shape finished after its first point is thrown away, with nothing left in the undo history. |
| Rectangle | R | Drag a rectangle. Shift keeps it square, Alt draws from the center. |
| Ellipse | E | Drag an ellipse. Shift keeps it a circle, Alt draws from the center. |
Drawing tools stay active after each shape, so you can draw several in a row, and each new shape is selected when it is finished. The pointer is a crosshair over the image while a drawing tool is active. Press Escape, Enter or V to return to Select.
The Pen only edits the shape it is drawing. Click right beside another shape and a new shape starts there; the other shape is never touched. To continue an open shape, select it, then click one of its end points with the Pen. A short flick makes a corner: the Pen pulls handles only once you drag past a few pixels. With Auto-smooth on (shown while the Pen is picked), the shape curves through every point on its own and shows no handles.
Show Source shows the input image with the shapes drawn over it, and the mask is re-rendered when you let go, so dragging stays light. Turn it off to watch the mask itself update as you drag one shape. Moving, scaling or feathering two or more shapes at once always re-renders the mask when you let go.
Selecting
Section titled “Selecting”A shape you have not selected is one object: clicking it selects the whole shape. Once a shape is selected, its points appear and can be picked one by one.
| Gesture | Effect |
|---|---|
| Click a shape’s edge, or inside it | Selects that shape. Inside, the smallest shape under the pointer wins, so a hole or a small shape is easy to pick inside a large one. |
| Click a point of a selected shape | Selects that point. |
| Double-click a point | Selects every point of that shape. |
| Shift+click a shape or point | Adds it to the selection, or removes it. |
| Alt+click a shape | Selects the next shape under the pointer, to reach shapes stacked on top of each other. |
| Drag inside a shape, or on empty canvas | Draws a selection box. It selects the points inside it; a rectangle or ellipse is selected when the box holds all of it. |
| Shift+drag a box | Adds to the selection. |
| Alt+drag a box | Removes from the selection. |
| Alt+drag a shape’s edge | Duplicates the shape and moves the copy, leaving the original where it was. Dragging the edge of a selected shape duplicates every selected shape. Each copy lands right after its original in the shape list and becomes the selection; Escape while dragging cancels it. |
| Click empty canvas | Clears the selection. |
Nothing moves until you drag a few pixels, so a tap with a pen or a trackpad click never nudges a shape. Selecting never marks the project changed and never re-renders the mask, and Undo and Redo bring back the selection that went with each edit.
| Command | Key | Effect |
|---|---|---|
| Select All | Ctrl+A | Selects every visible, unlocked shape. |
| Reselect | Ctrl+Shift+D | Brings back the selection you had before the last one. |
| Invert Selection | Ctrl+Shift+I | Selects every shape that is not selected, and clears the rest. |
| Delete | Delete or Backspace | Deletes the selected points, or the selected shapes. A closed shape left with fewer than three points is deleted. |
Escape steps back one thing at a time: it cancels a drag in progress, then finishes a shape the Pen is drawing, then leaves a drawing tool for Select, then clears the selection.
Moving, scaling and rotating
Section titled “Moving, scaling and rotating”| Gesture | Effect |
|---|---|
| Drag a shape’s edge | Moves every selected shape. An unselected shape is selected first. |
| Drag a selected point | Moves every selected point and every selected shape together. |
| Hold Shift after the drag starts | Locks the move to one axis. |
| Hold Ctrl after the drag starts | Snaps the point you grabbed to guides, the canvas edges and center, and the points of other shapes. |
| Arrow keys | Move the selection one image pixel, or ten with Shift. Several presses in a row are one undo step (see Arrow-key nudging). |
The transform box. Select two or more points, or any whole shape, and a box appears around the selection:
- Drag a square on a corner or an edge to scale. Hold Shift to keep the proportions; hold Alt when you press to scale about the center of the box instead of the pivot. Dragging past the opposite side flips the selection.
- Drag just outside a corner to rotate. Hold Shift to turn in 15 degree steps.
- Drag the box’s border to move the selection.
- The pivot, a crosshair at the center, is the point the selection scales and rotates about. Drag it anywhere; it snaps to points and to the box’s corners, edge centers and center. Double-click it to put it back in the center.
After a rotation the box keeps its angle, so you can stretch a turned shape along its own length. Every scale, rotation and move is one undo step, and Escape during the drag puts everything back.
Rectangles and ellipses stay rectangles and ellipses when you move or scale them. Rotating one turns it into a path shape in the same undo step, keeping its name, color, Combine, Grow, Feather, Opacity and Placement. Point gestures (adding, deleting, bending) do nothing on a rectangle or ellipse until then.
Points and handles
Section titled “Points and handles”A path point is either smooth (its two handles stay in line, so the curve flows through it) or a cusp (its handles move independently, so the curve can turn a corner). Alt changes the shape of a point, and Ctrl adds or removes points.
| Gesture | Effect |
|---|---|
| Drag a handle | Moves that handle. On a smooth point the opposite handle turns with it and keeps its own length. |
| Shift+drag a handle | Mirrors the opposite handle at the same length. |
| Alt+click a point | Makes it a cusp with both handles pulled in, so the shape takes a sharp corner. |
| Alt+drag a point | Pulls a fresh pair of smooth handles out of the point, in line and equal in length. This is also how a cusp becomes smooth again. |
| Alt+drag a handle | Breaks the pair: the point becomes a cusp that keeps both handles, and only the handle you drag moves. |
| Ctrl+click an edge, or double-click it | Adds a point there without changing the curve. To open a closed shape, use Open in the tool row. |
| Ctrl+drag an edge | Bends that stretch of the edge through the pointer. |
| Ctrl+click a point | Deletes it. Deleting the second-to-last point removes the shape. |
| Ctrl+click empty canvas | Adds a point to the nearer end of the selected open shape. |
Hold Ctrl to see points. While Ctrl is held, the shape under the pointer shows its points even when it is not selected, so Ctrl+click deletes one in one step without changing the selection.
Smooth Points and Corner Points in the tool row turn every selected point (every point of a whole selected shape) smooth or into a corner with no handles. Smooth Points gives each point the handles the automatic curve would have, so the curve keeps its look. They have no key of their own; you can assign one in the keyboard shortcuts.
Each shape’s edge keeps the color it was drawn with, and the same color is its swatch in the shape list.
Auto-smooth shapes
Section titled “Auto-smooth shapes”Points placed with Auto-smooth on have no handles: the shape curves through them on its own, even as you move them. Alt+click or Alt+drag converts just that one point, and the rest of the shape stays auto-smoothed. Auto Smooth in the Selection section switches whole shapes: off keeps the curve exactly as it is and gives every point editable handles, and on hands every point back to the automatic curve. A shape with a mix of converted and automatic points shows as off.
Feather on the canvas
Section titled “Feather on the canvas”A selected closed shape shows a small knob on a stem, in the shape’s color, with a dashed line where the feather reaches. Drag the knob, or the dashed line, to change Feather: outward feathers more, inward less, whatever the shape’s Placement. With several shapes selected, each changes by the same amount from where it started, and a readout beside the pointer says how much (Feather +4 px, 4 shapes). Double-click the knob to set Feather to 0 on every selected shape. The knob is there at Feather 0 too, so a new shape can be feathered on the canvas.
Copy Path and Paste Path
Section titled “Copy Path and Paste Path”Copy Path in the tool row copies the selected shapes drawn with the Pen (not rectangles or ellipses); with only some points selected, it copies their whole shapes. On the right-click menu of a row in the shape list, Copy Path copies that row’s shape. Paste Path adds the copied paths as new shapes at their own pixel positions and selects them. Paths also paste between Roto, Path Warp, and Scatter’s Path mode in either direction, so text, ribbons, and scattered copies can follow the curve you drew here. See Along a Path.
Output: mask or masked image
Section titled “Output: mask or masked image”Output Type chooses what the node publishes.
- Mask, the default, publishes the shapes as a grayscale mask.
- Image, available once an image is connected to the input, publishes that image with the mask written into its alpha, so no Mask Apply node is needed downstream.
With Output Type set to Image, Apply picks how the mask meets the image’s existing alpha: Cut Out replaces it, and Intersect multiplies it by the mask, keeping only where both cover, in proportion to each, so soft edges blend smoothly where they cross. Disconnect the image and the control disables with a notice; the mask is published meanwhile, and Image is remembered for when an image is reconnected. Existing projects keep the mask output. Show Source keeps its meaning in Image mode, so turn it off to see the masked image itself.
Parameters
Section titled “Parameters”Pins
Output
Output mask width in pixels
Output mask height in pixels
- Mask: the shapes as a grayscale mask.
- Image: the connected image with the mask written into its alpha, as Mask Apply would do.
How the mask is applied to the image alpha channel:
- Cut Out: replaces alpha with mask value.
- Intersect: multiplies existing alpha by mask, keeping only where both cover.
Invert the entire mask output
Shapes
Auto-smooth bezier handles when adding pen points
Bezier shape list (edited via the canvas manipulator)
Global
Show the mask as a tinted overlay on the input
The shape list and the Selection section
Section titled “The shape list and the Selection section”The Parameters panel lists every shape. Each row has the shape’s color, an eye to hide it, a padlock to lock it, its name and kind, and a delete button.
- Click a row to select that shape, Ctrl+click to add or remove it, Shift+click to select a run of rows. The list and the Preview share one selection.
- A hidden shape leaves the mask and cannot be picked in the Preview. A locked shape stays in the mask but cannot be picked or moved in the Preview. Both can still be selected in the list to change their settings; the tool row says “Locked” when a selected shape cannot move.
- Delete Selected in the tool row removes the selected shapes or points, and Clear All removes every shape and picks the Pen. Undo brings them back.
The Selection section below the list edits every selected shape at once. Its first line counts the selection (3 shapes selected, or 14 points in 3 shapes), and Name appears for a single shape. Each row shows the first shape’s value and says Mixed when the selected shapes differ. Dragging a slider adds the same change to each shape’s own value, and typing a number or picking a choice sets every shape to it.
| Control | What it does |
|---|---|
| Name | A label for the shape, so a graph with several is readable. |
| Combine | Add merges the shape into the mask; Subtract cuts it out. New shapes default to Add. |
| Grow (px) | Expands (positive) or shrinks (negative) the shape’s mask without editing the path. Applied before feathering. |
| Feather (px) | Blur radius around the shape edge. |
| Placement | Where the feathered edge sits relative to the path. Outside keeps the shape solid up to the path and softens outward, Centered softens equally to both sides, and Inside softens entirely within the path. |
| Opacity (%) | How strongly the shape contributes to the mask. |
| Auto Smooth | Hands the shape’s points to the automatic curve, or bakes them into editable handles (see Auto-smooth shapes). |
Newly drawn shapes feather Outside, so feathering never eats into the shape. Shapes saved before Placement existed keep their Centered feathering. Double-click or right-click any of these sliders to reset it.
Modifier keys on macOS and Linux
Section titled “Modifier keys on macOS and Linux”On macOS, Ctrl in every gesture on this page is the Command key, and Alt is Option. The keyboard shortcuts use Command too (Cmd+A selects all).
On Linux, many window managers use Alt+drag to move windows, so Alt+drag may never reach ArcBrush. To remove shapes from a selection there, Shift+click them instead, or use Invert Selection; to duplicate a shape, use Copy and Paste.
Usage Tips
Section titled “Usage Tips”- Reach for Grow instead of redrawing when a mask sits a few pixels inside or outside the object.
- Pair a small positive Grow with an Inside placement to soften an edge while keeping the mask’s coverage.
- Roto also draws the pieces for Separate when a texture set has no cutout of its own: wire the mask into Separate’s mask input.