How to Use Rotoscoping in Kdenlive to Mask Objects

This article provides a step-by-step guide on how to isolate or mask out objects in your video footage using the Rotoscoping filter in Kdenlive. You will learn how to apply the filter, draw a custom mask around your target subject, animate the mask to track motion using keyframes, and configure the settings to achieve a clean cut-out or target specific effects.

Step 1: Add the Rotoscoping Filter

  1. Import your video clip into Kdenlive and drag it onto the timeline.
  2. Go to the Effects tab (usually located in the bottom-left or top-left pane). If you cannot see it, enable it via View > Effects.
  3. In the search bar of the Effects tab, type Rotoscoping.
  4. Drag and drop the Rotoscoping (or Rotoscoping (Mask)) filter directly onto your video clip in the timeline.

Step 2: Draw the Mask Around the Object

  1. Select the video clip in your timeline to display its properties in the Effect/Composition Stack panel.
  2. Click on the Project Monitor to make it active.
  3. Left-click around the object you want to mask out to create control points. Continue clicking to outline the entire shape of the object.
  4. To complete and close the mask loop, right-click anywhere on the Project Monitor. The shape will close, connecting your last point to your first point.

Step 3: Configure the Mask Settings

In the Effect/Composition Stack panel, you can adjust how the mask behaves: * Mode: Choose how the mask interacts with the video. “Alpha” is commonly used to make everything outside the mask transparent (ideal for isolating an object). * Feather width: Adjust this slider to soften the edges of the mask so it blends more naturally with the background. * Pass: Choose whether to keep the inside of the mask (Write On) or the outside of the mask (Clear).

Step 4: Animate the Mask (Tracking Motion)

If the object in your video moves, you must animate the mask to follow it using keyframes: 1. In the Rotoscoping effect panel, look at the built-in keyframe timeline. 2. Position the playhead at the start of the clip and adjust your mask points to fit the object. 3. Move the playhead forward in time to a point where the object has moved. 4. In the Project Monitor, click and drag the control points to realign the mask with the object. Kdenlive will automatically create a new keyframe. 5. Repeat this process at regular intervals. Kdenlive will automatically interpolate (smoothly transition) the shape of the mask between your keyframes.

Step 5: Overlay and Finalize

If you used the mask to create transparency (Alpha mode): 1. Place the masked clip on an upper video track (e.g., V2). 2. Place a background video, image, or color clip on the track directly below it (e.g., V1). 3. Play back the timeline to ensure the masked object aligns perfectly with the new background.