Combine A.I. + Manual Masks in Resolve Fusion
DaVinci Resolve Masks for Legal Blurring
Today, I want to help you up-level your DaVinci Resolve Fusion masking skills for blurring a face behind foreground occlusions and tracking off-screen. You'll learn how to perform stabilized rotoscoping, gradient extrapolation of motion tracking data, and how to combine an AI magic mask with a manual bspline shape mask. Footage used in the tutorial can be downloaded on this website here by joining the cutting club, where you can gain access to the footage used in many VFX-related tutorials taught on this channel. It is a great way to support my efforts to provide free YouTube tutorials.
Step 1 - Tracking
Run the MediaIn1 directly into the background of the regular point tracker tool.
Sometimes, you will get better results using the older contrast, pattern-based tracker instead of the new AI intellitrack. For this example, I found the old tracker to work better.
Position the pattern over the nose of the women in the shot that needs to be blurred and track forward one frame at a time.
If the green displacement path starts to slide off, reposition the tracker pattern box and overwrite the existing tracking data.
Often, you will need to delete bad tracking keyframes by opening the spline editor, selecting them, and hitting the delete button on the keyboard.
To track off the edge of the screen, right-click and choose “gradient extrapolation.” Gradient Extrapolation will continue the speed and direction from the last keyframes.
To track behind a foreground object or occlusion, stop tracking on the last good visible frame and move the playhead to a moment after the pattern is visible again to place the tracking pattern box back over the nose and begin tracking again with the track forward frame by frame button. Resolve Fusion will interpolate between two keyframes and provide a smooth motion. If the timing needs to be adjusted for the object between the two keyframes, you can adjust the tangent handles in the spline editor panel.
Step 2 - Stabilizing
After you have a solid track, we want to stabilize the motion. This can be done in the native tracking tool by setting the operation match move setting to BG only. However, this isn’t very flexible because it only gives you three matchmove options: the start frame, the end frame, and the selected frame (which really means the frame you started tracking on).
Instead, I prefer using the Macro from Millolab found in Fusion Reactor. The tool is called the ml_TrackerTool and allows you to change the reference frame at any time or to use as many instances of the original tracking data downstream in your Fusion comp as you like. I plug my MediaIn1 node directly into the input of the ml_TrackerTool.
I move the playhead to the frame I want to draw my mask on. Ideally, it's a frame in which you can clearly see all of the edges. I picked frame 70 and set that as the reference frame after dragging the Fusion tracker tool into the empty tracker space on the ml_TrackerTool node. This stabilizes the motion around frame 70.
Step 3 - Rotoscoping
To rotoscope, now that the footage is stabilized, just click to draw a B-spline shape around the woman’s head and close it up. Shapes in Fusion are already primed for keyframe animation over time. You want to create the B—spline shape while it is not connected but while looking at the stabilized footage in the viewer.
So, to change the shape over time, move to a new frame when the shape does not line up, move the edge, and you should see the animation of the b-spline match the footage. Ideally, you want to use the fewest keyframes as possible.
After you’ve finished keyframing the shape, unhook the MediaIn1 from the ml_TrackerTool, plug the B-Spline shape into it, and change the mode to Matchmove.
Step 4 - Magic Mask
Start by also feeding the MediaIn1 into a magic mask node.
Move to a frame that visibly shows the entire foreground occlusion, and use the eyedropper to make a quick rough swipe over some of the contrast areas to add a positive stroke.
Change the mode to better for a “better” softer mask, and run the track forward and backward.
To ensure you are only using the mask or alpha output of the magic mask tool, I add a bitmap node after the magic mask is set to alpha, which cuts out the RGB channels downstream.
Step 5 - Matte Control
Fusion allows you to combine masks in many ways, but one great thing to know is the matte control node.
Send the output of the manual rotoscope from the ml_TrackerTool into the matte control yellow input.
And send the bitmap output from the magic mask to the matte control green foreground input.
Then simply change the operation mode to combine alpha and subtract. The result should be a mask covering the woman’s face but not the guy walking in front of her.
Step 6 - Mosaic Blur
Add a blur or mosaic blur node after the MediaIn1 to blur the footage.
Finally, you can send the output of the Matte Control node to the mask input of the Blur node to restrict the blur to only a small area of the woman’s face.
Optionally, if you would like to send the mask to the color page instead, you can add a second MediaOut2 node and send the mask alpha matte there. On the color page, right-click to add a source.
The new second source can be connected to a blue mask input on the color page as if it were any other external matte from a rotoscoping vendor.
