While the Roto Brush tool primarily creates a segmentation or alpha channel to isolate a subject rather than traditional mask paths, you can easily convert the result of your Roto Brush work into editable mask shapes in Adobe After Effects. This process utilizes the Auto Trace feature, which analyzes the layer's alpha channel (created by Roto Brush) and generates mask paths that follow the outline.
Turning your Roto Brush result into masks provides the flexibility to manipulate the shape further, export paths, or use the outlines in ways the Roto Brush effect alone might not allow.
Converting Roto Brush Output to Masks
As highlighted in the provided reference, the key to creating masks from your Roto Brush segmentation is using the Auto Trace function. Here are the steps:
- Apply and Refine Roto Brush: First, ensure you have successfully applied the Roto Brush tool to your layer and refined the selection across your desired frames or work area. The Roto Brush effect must be active and isolating your subject correctly.
- Select Your Layer: In your timeline, select the layer to which you applied the Roto Brush effect.
- Access Auto Trace: Go to the top menu bar.
- Click on Layer.
- From the dropdown menu, select Auto-Trace....
- Configure Auto Trace Settings: A dialog box will appear with various options for the tracing process. Based on the reference and common usage for Roto Brush conversion, configure the settings as follows:
- Apply To: Ensure Current Layer is selected (or confirm you are working on the correct layer).
- Time Segmentation: Check the work area option. This tells After Effects to generate masks only for the duration of your composition's work area, which is typically where your Roto Brush work is finalized.
- Options: It's generally recommended to leave most other options (like Tolerance, Minimum Area, Corner Angle) at their defaults or adjust slightly if needed, but the most crucial setting for applying masks directly is:
- Apply to New Layer: Uncheck this option. As the reference specifies, unchecking this ensures the generated masks are created directly on your selected layer, rather than creating a separate solid layer with masks.
- Execute Auto Trace: Click the OK button to start the process.
- Wait for Processing: After Effects will analyze the alpha channel generated by the Roto Brush effect over your specified work area and create corresponding mask paths on your layer. This process might take some time depending on the complexity of the outline and the length of the work area.
Once complete, you will find new mask properties added to your layer in the timeline, each containing path data that follows the outline defined by your Roto Brush work for each frame.
By following these steps, you effectively transform the isolation provided by the Roto Brush tool into traditional, editable mask shapes.
