Animating graphic elements created in applications such as Adobe Photoshop and Illustrator, is relatively simple, as is working with straight video footage. However, when you need to combine these two different types of media, motion and camera tracking are tools you can use.
Lesson 10: Tracking and Stabilizing Footage
Animating graphic elements created in applications such as Adobe Photoshop and Illustrator, is relatively simple, as is working with straight video footage. However, when you need to combine these two different types of media, motion and camera tracking are tools you can use.
What you’ll learn in this lesson:
• Understanding how video stabilization and camera tracking work
• Stabilizing video footage
• Tracking a camera in 3D space
• Applying tracked camera data to composite graphics into a video frame.
Starting up
You will work with several files from the ae10lessons folder in this lesson. Make sure that you have loaded the aelessons folder onto your hard drive fromwww.digitalclassroombooks.com/epub/aftereffectscs6. See “Loading lesson files” in the Starting up section of this book.
Setting up
As you work in After Effects, you will inevitably open and close many panels, depending on the type of project you are creating. However, when working through the projects in this book, it is important to have an interface that matches the lessons. To this end, you should always reset your workspace to the preset Standard configuration.
1 Choose Window > Workspace > Standard to set your current workspace configuration.
2 Choose Window > Workspace > Reset “Standard” to reset the standard workspace in case you have modified it at some point.
Understanding Video Stabilization and Tracking
Video stabilization and tracking are terms for several separate, but very similar, processes found in Adobe After Effects. In some cases, such as working with the point-based Motion Stabilizer and Motion tracker, they are actually the exact same command, but with different targets and end results. Initially, all stabilization and tracking effects attempt to analyze a video sequence and extract useful data from it. Upon closer inspection, both have several distinct divisions that you should be aware of:
Warp Stabilizer: The Warp Stabilizer is used to remove jittery motion that is most often caused by camera movement. This effect makes it possible to correct handheld and shaky footage, turning it into a series of steady, smooth shots that appear as though they had been captured using a tripod or dolly.
3D Camera Tracking: The 3D Camera Tracker is an effect that analyzes a video sequence and attempts to extract data about the position and motion of the camera that shot the footage. You can then use this data to create a Camera in After Effects that should correctly mimic the movement of the camera in the video sequence. This allows you to correctly composite 3D layers on top of your 2D video footage.
Using the Warp Stabilizer
The Warp Stabilizer was first introduced in After Effects CS 5.5. This effects runs as a background process and begins immediately upon being applied to a layer. There are several options that you should be familiar with when using the Warp Stabilizer.
Result: This property controls the intended results of the Warp Stabilizer. The only two options are Smooth Motion and No Motion. Smooth Motion retains the original camera movement of the footage, but attempts to make it appear smoother and less jerky. The No Motion setting attempts to remove all camera movement from the video sequence.
Smoothness: Controls how much of the original footage’s camera motion is stabilized. Lower values preserve more of the camera’s original motion, while higher values produce a smoother result. Note that this property is only available when the Result is set to Smooth Motion.
Method: Specifies the type of operation the Warp Stabilizer attempts to perform on the footage.
Position: Tracking is based only the X and Y position of the content of your footage and is the simplest type of stabilization that can be performed.
Position, Scale, and Rotation: Stabilization is based on all three of these properties and can provide a better result when the camera is moving through the scene.
Perspective: Tracking can better stabilize footage that might have perspective shifts.
Subspace Warp: Attempts to warp different areas of the video frame individually to stabilize the entire frame. If the Stabilizer cannot locate enough points to perform the selected stabilization, it will fall back to the preceding stabilization type.
Framing: The Framing property specifies how the borders, the moving outside edges of the video frame that result from the stabilization effect, appear when the stabilizing result is viewed.
Stabilize Only: Displays the entire frame including the moving edges. This is good when you want to see how much work is being done by the Warp Stabilizer.
Stabilize, Crop: Crops the moving Edges without scaling them. This results in a stabilized video frame that is smaller in size than the original video frame.
Stabilize, Crop, Auto-scale: The default result of the Warp Stabilizer; crops the moving edges and then scales the resulting stabilized image to fill the entire size of the original video frame.
Stabilize, Synthesize Edges: Fills the space created by the moving edges with content extrapolated from adjacent frames. Users of Adobe Photoshop might find it similar to an unrelated effect called Content Aware Fill.
In this section of the lesson, you will apply the Warp Stabilizer effect to a video clip. After Effects is often used to quickly correct shaky or otherwise unusable footage so it can then be integrated into a video editing project.
1 Choose File > Open Project and navigate to the ae10lessons folder. Locate the project called Using the Warp Stabilizer.aep and double-click it to open the file. This project contains a single video file called Park Scene-Shaky.mpeg. It is a ten-second, 1080P high-definition video file.
2 In the Project panel, locate the Park Scene-Shaky file and then drag it to the Create a new Composition button located at the bottom of the panel. This creates a new composition based on the properties of the video file. It will exactly match the file’s dimensions, frame rate, and duration. This is a good technique to use in a situation where the goal is to apply an effect to a video clip, and then render it immediately so it can be used in a video editing application such as Adobe Premiere Pro or Apple Final Cut Pro.
3 Choose File > Save As and navigate to the ae10lessons folder. Rename the project Using the Warp Stabilizer-working.aep, and then click the Save button.
4 In the Project panel, the new Composition called Park Scene-Shaky was created inside the video folder along with the video clip. Click the composition and drag it outside of the folder.
Folders are a great way to keep the Project panel organized.
5 When you created the new Composition in the preceding step, it automatically became active in the Timeline and Composition panels simultaneously.
Choose Composition > Preview > RAM Preview so that you can take a look at the unstabilized video footage. Notice that the video sequence is very shaky; a situation that is very common when working without a tripod or dolly. In this case, the camera person was using a hand-held camera while walking along the roadway.
Stop the preview by clicking in the Timeline panel and then click on the Park-Shaky.mpeg layer in the Timeline to make it active.
6 With the video layer selected, choose Animation > Warp Stabilizer. This applies the Warp Stabilizer effect, which immediately begins analyzing the contents of the layer based on its default settings. If you know that the default settings are not a good choice for your particular footage, you can cancel the effect via the Effect Controls panel that automatically opens when you apply the Warp Stabilizer. Keep in mind the only way you could possibly know that the default settings will not work for your sequence is if you have performed stabilization on similar footage in the past. It is often a good practice to apply the Warp Stabilizer with the default settings and then adjust them as necessary.
The warp stabilizer runs as a background effect.
Since the Warp Stabilizer runs as a background effect, you can perform other actions in After Effects while waiting for it to complete. If you hide the Composition panel that is showing you the results of the effect, you will receive notification via the Info panel when the Warp Stabilizer is done. Depending on your system configuration, this background process can take quite some time to complete.
7 Once the Warp Stabilizer effect has completed analyzing and adjusting the footage, Choose Composition > Preview > RAM Preview so that you can take a look at how the footage has been stabilized. You will see that even at the effect’s default settings, the footage looks much better than what was originally shot. While there is still movement in the video sequence, the frantic movement has been signifcantly softened.
Press the spacebar on the keyboard to stop the preview.
8 Choose File > Save As, and if necessary navigate to the ae10lessons folder. Rename this file Using the Warp Stabilizer-complete.aep and click the Save button.
You can now close this file by choosing File > Close Project.
Many users of After Effects find that the default settings of the Warp Stabilizer are actually very good when applied. It is a phenomenal leap beyond the capabilities of the legacy Point Stabilization that the application used to favor. With this effect, many quick stabilization jobs have become one-click operations. These default settings always aim for the highest possible level of stabilization. It uses the sub space warp method to warp different areas of the video frame individually in an attempt to stabilize the entire frame.
Using the 3D Camera Tracker
The 3D Camera Tracker effect analyzes video or image sequences to extract camera motion and three-dimensional scene data. This extracted data can then be used to create an After Effects camera layer, allowing you to properly composite three-dimensional layers on top of existing two-dimensional footage. The 3D Camera Tracker effect shares its tracking code with the Warp Stabilizer, and like that effect, performs its analysis as a background process.
The effect automatically runs at its default settings. If you know these are not appropriate for your current footage, you can stop the effect using the Cancel button located in the Effects Controls panel.
The 3D Camera Tracker effect has several controls that you should become familiar with.
Shot Type: this property is used to specify the angle of view used in the source video footage. You can choose from a fixed horizontal angle of view, variable zoom, or a specific horizontal angle of view. If you set the property to a specific horizontal angle of view, you can input the exact angle of view the solver should use in its calculations.
Show Track Points: toggles between showing the 3D solved, perspective-hinted track points, and the 2D source points, without hinting perspective.
Render Track Points: controls whether the solved track points are rendered during RAM Preview. The track points are always visible when the effect is selected in the Effects Controls panel or Timeline, even if this option is not selected.
Create Camera: builds an After Effects Camera layer from the solved camera data.
Integrating graphics with live-action footage can be quite difficult. If your camera is locked so it doesn’t move, adding graphics created in After Effects, Photoshop, or Illustrator can be a straight-forward process. However, when you are dealing with video footage in which the camera is moving through the environment, you need an application that can perform 3D camera tracking, also called match moving. This technique analyzes the video sequence and attempts to extract data about the relationship between elements in the footage. Once this data has been processed, a virtual camera can be created that matches the movement and positioning of the real-world camera, allowing graphics to be accurately matched to the video footage.
Prior to the CS6 release, this technology wasn’t available to After Effects users natively, but was provided through third-party plug-ins or other applications. Now that this feature is available natively within After Effects, any user can easily composite graphics into video footage.
In this part of the lesson, you will run the 3D Camera Tracker effect on a video sequence of a camera dollying down a school hallway, and then use the extracted data to composite two Photoshop graphics into the scene.
1 Choose File > Open Project and navigate to the ae10lessons folder. Locate the project called Using the 3D Camera Tracker.aep and double-click it to open the file. The main composition in this project is called On Education. It contains a video sequence called Dolly Down Hallway, and two secondary Compositions called Quote 1 and Quote 2.
2 Choose File > Save As and navigate to the ae10lessons folder. Rename the project Using the 3D Camera Tracker-working.aep, and then click the Save button.
3 If necessary, double-click the On Education composition in the Project panel to make it active in the Timeline and Composition panels. This Composition contains three layers: Quote 1 and Quote 2, which are hidden, and a video layer called Dolly Down Hallway.mpeg.
Layers in After Effects can contain any type of media, including other Compositions.
4 Turn on the visibility of the two hidden layers by clicking the visibility switch located to the left of each layer. Drag the playhead back and forth along the Timeline; notice that the two graphic layers remain stationary, making it impossible to believe that they are in the same scene as the video. This is what the 3D Camera Tracker can help you correct. Hide the two Composition layers (Quote 1 and Quote 2) before you continue.
5 In the Timeline panel, click the video layer to highlight it, and then choose Animation > Track Camera.
The 3D Camera Tracker effect runs as a background process just like the Warp Stabilizer.
Analyzing a video file to extract camera data is a time-consuming, processor-intensive process that can take time to complete. The Camera Tracker runs as a background process, thus allowing you to continue with other tasks while it works on your footage.
The completed effects with Track Points visible on your footage.
6 Once the effect has completed processing, a series of 3D track points will be visible on your video footage. These points represent different tracked pixels in the video footage and their relative positions in three-dimensional space. Move the playhead back and forth over the Timeline; notice that the points change as the camera moves down the hallway. As you move your cursor around the Composition panel, you will notice a selection ring appear when you are between multiple track points. This indicator shows the perspective distortion that exists between multiple points.
Track points are only visible when the 3D Camera Tracker effect is highlighted in the Effect Controls panel.
You can assign 3D layers to either a single track point or to multiple ones. If you select multiple points, the application will warp the layer to account for perspective distortion, allowing you to have After Effects layers automatically adjust to the perspective in your video footage.
7 Choose File > Save. Do not close this file; you will need it in the next part of this lesson, where you will create an After Effects Camera layer that mimics the movements of the real-life camera from the footage.
Attaching 3D layers to Track Points
Now that you have tracked the movement of a camera in the video file, you will use the created track points to position 3D layers so they can appear to transform in the same way that the rest of the video sequence does. Once you have your 3D track points, the next step of the compositing process begins. After Effects allows you to create a camera layer that matches the movement of the camera in your video sequence.
Additionally, you can create three types of 3D layers; null, solid and text. You can then position them to match the position of any visible track point.
Each of these three layer types can be useful for a number of different situations. A null layer for example, is a helper object; it can have all the transform properties of any visual layer (position, scale, etc.) but it does not render and is therefore a useful layer to use as the parent of a visual layer. Solid layers can be used as graphics (color fields or color boxes) or as surfaces to receive shadows from 3D objects. Text layers allow you to have text in 3D space that seems to move along with the movement of the camera through your video footage.
1 With the Using the 3D Camera Tracker-working.aep file still open, move the playhead to the beginning (0;00;00;00) of the Timeline, if necessary.
2 In the Composition panel, right-click on one of the left most track points and choose Create Null and Camera from the menu that appears.
You can create solid, null and text layers at the position of any track point.
When you right-click a track point, you can choose to create a null, solid, or text layer at the current position of that track point.
This command does several things: it creates a Camera layer from the Camera data extracted from the scene, and it creates a 3D Null layer that is placed at the position of the selected track point.
The Camera layer is necessary so that your graphics will appear to move as the camera in the video scene moves.
3 In the Timeline panel, locate the layer called Quote 1 and unhide it. Then, click the layer’s 3D switch to convert it from a two-dimensional to a three-dimensional layer. 3D layers are necessary for anything you want to composite into a video scene, since only they are affected by Camera layers.
Remember any layer you want to attach to a track point has to be 3D.
4 Press and hold the Shift key on your keyboard, click the Quote 1 layers Parent drop-down menu, and choose Track Null 1 to parent the layer to the Null you created in a preceding step.
Choose Track Null 1 from the Parent drop-down menu.
Pressing and holding the Shift key while setting a layer parent moves the child layer (Quote 1 in this case) to the position of the parent. Pressing and holding the Alt (Windows) or Option (Mac OS) key allows the child layers to maintain their current Transformation values.
The Quote 1 layer’s Anchor Point moves to the exact position of the Null layer.
5 Because of the effect of perspective, the Quote 1 layer is now much larger and extends outside the video frame. You will correct this by resizing it. If it is not already selected, click the Quote 1 layer to highlight it, and then press the S key on your keyboard to reveal the layer’s Scale property. Click any of the three property values and change it to 50.
Since the Constrain Proportions switch is enabled, changing any scale property value changes them all.
6 In the Timeline panel, right-click the Track Null 1 layer and choose Rename from the menu that appears. Change the Null’s name to Quote 1 Tracker.
7 RAM Preview the Timeline by choosing Composition > Preview > RAM Preview. Notice that the graphic now seems to move along with the video footage until you can no longer see it as the dolly moves past it.
8 Choose File > Save. You can now close this file.
Congratulations! You have finished this lesson.
Self study
1 Import your own video footage that needs stabilization and run the Warp Stabilizer effect on it. Depending on the type of correction you need to create, you might want to use a stabilization method other than Subspace Warp. For example, if you are only trying to keep a single unmoving object centered in the video frame, a simpler method, such as Position, would be better for this task.
2 Continue to work on the Using the 3D Camera Tracker.aep project, or use your own footage. Try adding a 3D text layer to your scene by right-clicking a track point and choosing Create Text from the menu that appears.
Review
Questions
1 In Adobe After Effects, what is the purpose of the Warp Stabilizer?
2 What is the purpose of the 3D Camera Tracker?
3 When you right-click a solved track point, what are the three types of layers you can create?
Answers
1 The Warp Stabilizer is used to remove jittery motion most often caused by camera movement.
2 The 3D Camera Tracker effect analyzes video or image sequences to extract camera motion and three-dimensional scene data. This data can then be used to create a Camera layer, allowing you to properly composite graphics into a video sequence.
3 When you right-click a track point, you can choose to create a null, solid, or text layer at the current position of that track point.
