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Resolve 18 is filled with some really interesting features that can take your edit to the next level. Watch the video or read on to learn how to effectively use the Surface Tracker and Depth Map effects in your workflow.
For this tutorial, we’ll be using this beautiful hiking shot below. You’ll learn how to use the Surface Tracker to remove the trail marker that’s painted on the rock, and the Depth Map effect to color grade the sky differently from the foreground in this image. Let’s start with removing the trail marker.
Open up your effects browser, find the Surface Tracker and drag it into the node tree. The Surface Tracker has two inputs – input one is for the image that you are tracking and attempting to patch. Input two is for the patch that you’re going to project onto the Surface Tracker. For the time being, feed input one and input two the same image, it’ll become clearer why we’re doing that later.
When you select the Surface Tracker node, the OpenFX overlay is automatically selected in your viewer. As shown in the image above, by clicking on the preview of the clip, you can create the boundary of the surface track. In this case, we’ve deliberately chosen to do this on the last frame of the clip, because the camera’s pushing closer and you get the best view of the trail marker on the last frame of the clip.
Next, head over to the mesh tab. There’s two different ways for Resolve to generate this mesh: the first is automatic (1), the second is using a uniform grid. For this example, stick with automatic point locations, because there’s plenty of nice crisp features for Resolve to track. Now, go to the track tab, and change the quality from faster to better (2). And because we’re on the last frame of video, you’ll want to click track backwards (3).
Now, we can head to the results tab. The Surface Tracker is currently set to warping input two onto input one (4) – it’s basically taking a snapshot of that second input, just one single frame, and warping it onto that surface as the video plays out.
Which frame is it using? At the moment, it’s currently using the first frame, so switch the overlay source to our reference frame. Because you started the track from the last frame of the video, by default, that frame has been set as the reference frame (5). You can see here that reference frame is frame 452 (6). It’s pretty easy to change your reference frame, just position the playhead and click, set to current.
At this point, you might be wondering why the trail marker is just as visible as ever. This is because we’re now going to reposition the overlay that is being applied to the Surface Tracker, to finally get the effect we want.
You can shift the overlay using sliders, or alternatively, just by clicking and dragging on the canvas (7). When you move the canvas around be careful, if you click and drag on the red lines, you will warp or distort the image. But if you click somewhere in the middle, it’ll just do a simple translation.
We’ve got a nice clean patch of rock under the trail marker, so move the overlay up to use the clean rock to patch the trail marker. Adjust the softness so you don’t get a hard edge on the Surface Tracker’s bounds (8). Finally, pipe the patch through a corrector node (9), and use a little bit of gamma to match the rocks better.
Next, let’s have a look at the Depth Map effect. Start by dragging the effect into your notary. At the moment, the Depth Map effect is a little bit processor intensive, so get ready to wait a while and to put up with slower playback.
As you can see by the preview next to the color wheels, it’s done a pretty good job of working out the depth in the scene. Because this is an OpenFX node, it’s not a corrector node, so you can’t apply any corrections to it.
What you need to do is send the alpha channel from this node to an ordinary corrector node, and then you can use it to make adjustments. If you head over to node five and turn on highlight mode, you’ll see that it is just selecting the foreground of the image – that’s easy for me to fix in the node key controls, you can just invert the key (1).
This isn’t particularly helpful at the moment – although it is selecting the sky, it’s also selecting a lot of the foreground. You’ll notice though that the foreground becomes more transparent the closer we get to the camera.
Let’s head back to the Depth Map node. Turn your preview back on (2), and check the box ‘adjust map levels’ (3). By manipulating the near limit and the far limit, you can make the Depth Map more aggressive.
It’s basically an alpha map – white represents parts of the image that are going to be opaque. Black represents parts of the image that are going to be transparent (with the caveat that you’ve flipped the key in your corrector node). Turn the Depth Map preview back off and go back to corrector node number five and drive some cyan and blue into the gamma (4).
Next, grab another corrector node, connect to the alpha channels, and select a power gradient (5). Use this just to add a little bit of a gradient to the sky, so it gets darker as you go up (6). No matter how far down you drag this gradient window, the grade is not going to affect the foreground of the image because you’re using the Depth Map to control its opacity.
The Final Result
This completes our editing for this shot – you can see the clip before editing, and a preview of the new clip below. When playing back the footage we found you get about six to eight frames per second on an M1 Max MacBook Pro. Maybe this will get a little bit better with subsequent releases that make the effect more efficient, but for now this is more than good enough for you to preview the effects of the grade.
Improving the Surface Mesh
Here are some other clips that allow us to look at the Surface Tracker and Depth Map effect in different scenarios. The Surface Tracker does not use your original source media, it uses whatever changes that you’ve made in any of the corrector nodes that are upstream from it. That means there are things that you can do that make your image easier or harder to track.
To demonstrate, in the clip shown below, every time you click ‘Regenerate Mesh’, Resolve will analyze the image and create a mesh based on the points of interest it finds, such as the jacket.
Look what happens if you turn on the upstream node that improves the contrast and the visibility of the jacket. When you come back into the mesh tab and hit regenerate mesh, you’ll see that it identifies way more points as a part of its mesh.
On flat images like the one below, the Depth Map effect is fantastic for isolating foreground subjects.
Try the isolation tools – in this case the subject is in the foreground, so you would decrease the target depth (1). The plugin won’t give you a pixel perfect mask, so it’s not a substitute for properly rotoscoping someone out. But if you head back to the Depth Map, you can turn on the map finesse post processing controls and add a little bit of blur (2). You can now manipulate just the foreground of this image.
Depth Map does a really good job even with complex scenes like the one below. In Depth Map, you can see the model walking, all of the sign posts, the and the bus that’s passing. These adjust map levels controls are really, really good, but there are other ways that you can manipulate the Depth Map.
For example, if you pipe its output to an ordinary corrector node, you can then manipulate that Depth Map using curves. There are scenarios where you might find that a more intuitive way of editing it.
When utilized correctly, Depth Mapping and Surface Tracking are powerful tools that can make color grading and other post-processing effects a lot easier!
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