Layered Patch Replacer Wire Removal

Learn how to remove objects in DaVinci Resolve using the Patch Replacer tool, even with the object touches a foreground element.

You can follow along with footage in provided by joining the cutting club here.

If you have ever used the Patch Replacer tool in the Fusion page of DaVinci Resolve Studio 20, you know it is essentially a powerful copy-and-paste tool. However, standard patching can become difficult when removing an object—like a wire—that is physically attached to a foreground element you want to keep.

In this guide, I will walk you through an advanced workflow to remove a wire attached to a laptop edge while maintaining perfect edges and color integrity.

The Basics: Isolating Patches

Before tackling complex wire removal, it is important to understand the basic workflow. When removing a simple object (like a logo), you typically use an ellipse or rectangle shape.

• Masking: To maintain the integrity of the original plate, you should isolate your patch. You can use a B-spline tool to cut out the area you are patching.

• Softening Edges: To blend the patch, hit D on your keyboard to activate "Make Double Polyline." Lasso select your points, hold O (for outer), and drag outward to add softness.

• Application: Connect the mask output to the blue input of the Patch Replacer and select "Multiply by Mask" in the inspector.

Advanced Removal: Using the Alpha Channel

For complex shapes like a wire, standard shapes won't cut it. We need to utilize the Alpha Channel functionality of the Patch Replacer.

Create the Alpha Input

We must first copy an alpha channel into the original image stream.

1. Trace the Object: Use a Polygon roto shape to click points closely around the wire you want to remove, including its shadow.

2. Copy the Alpha: Add a Matte Control node. Connect your original image to the yellow input and your Polygon to the green input.

3. Settings: In the Matte Control, go to "Combine" and set "Combine Alpha" to Copy.

4. Verify: You should see a checkerboard pattern, indicating the image is un-premultiplied (RGB values are still there), which allows the Patch Replacer to work.

The "Patches and Planes" Strategy

When setting up the Patch Replacer, change the Region Shape to Alpha.

If you are dealing with a moving shot, you must think in terms of "Patches and Planes"—specifically, what is furthest from the camera versus what is closest.

• The Problem: Backgrounds move slower than foregrounds due to parallax.

• The Solution: Overextend the patch. You should patch the background beyond the edge of the foreground object (the laptop). We will restore the laptop edge later.

Extending the Patch with Paint

Sometimes the source area for the patch doesn't line up perfectly. In these cases, use the Paint tool to manually clone the background.

1. Connect Paint: Place a Paint node after your Alpha Multiply node.

2. Set to Clone: Select the paintbrush, choose the "Stroke" tool (third icon), and set "Apply Mode" to Clone.

3. Source Tool Trick: To clone from the original image (before the patch), drag the upstream Gamut (or source) node into the "Source Tool" well in the Paint inspector.

4. Paint: Option-click to sample clean background and paint over the wire, purposely overextending past the edge of the foreground object.

The Secret to Perfect Edges: Smearing

Once the background is patched and overextended, you need to bring the foreground object back on top.

Restoring the Edge

1. Roto the Foreground: Use a new Polygon tool to trace the edge of the foreground element (the laptop).

2. Isolate: Use a Matte Control and Alpha Multiply (AML) node to copy this roto to the alpha channel and cut it out.

3. Composite: Merge this restored edge back over your background patch.

Fixing "White Specs" and Bad Colors

Often, simply cutting out the foreground leaves a mix of white or gray pixels at the very edge. To fix this and get perfect colors:

1. Paint Before the Mask: Insert a Paint node before the mask cuts out the object.

2. Smear Tool: Select the "Stroke" tool and choose Smear.

3. Push Pixels: Use the brush to push the internal edge pixels outward. This acts like a directed blur, filling the edge with the correct gray/color of the object rather than the background color.

This technique ensures that when the mask cuts the image, the pixels on the very edge are the correct color.

Final Compositing with "Atop"

You now have two patches: the background patch and the restored foreground edge. You should combine these before merging them back into the main stream.

1. Merge Node: Connect the restored edge output to the foreground (green) of a Merge node, and the background patch paint node to the background (yellow).

2. Operator "Atop": In the Merge node settings, change the Operator to Atop.

   • Why? This tells Resolve to look at the alpha channel of the background patch and only apply the foreground restore within that specific area.

By following this workflow, you remove the unwanted object, extend the background seamlessly behind the foreground, and restore a pristine edge with perfect color accuracy.