A common task is navigating around a map-like image. In this column, we’ll discuss three different approaches to this challenge: stroking a line, animating text elements along a path, and auto-orienting an object of your choosing along a path.
These techniques use features that are spread around Adobe After Effects. Our goal is to pull them together for you, and show the different approaches and options. We’ll be assuming a basic working knowledge of the program; you can also download and explore our final After Effects project (created for AE 6.5 and later) by clicking here (12.5 MB .zip file). Movies of the three techniques are included with the download.
Common Paths
We started with an image of a map created by Piri Re’is in 1513, and imagined a trade route that an ancient mariner may have taken. Our map is 960x1380 in size: considerably larger than our final output of 648x486. If you want to travel further or zoom in more on the details, you could start with an even larger map.
Our project includes four folders for Maps A through D. Each folder includes two compositions: Comp 1 holds the map and the animated element tracing the explorer’s route; this is then nested in Comp 2 where a motion control move is performed.
In each case, we started by drawing a mask shape that defined our path. First we dragged the map source image to the New Composition icon at the bottom of the Project window. This created a comp the same width and height as the image. We then set the comp’s duration to a touch longer than we thought we’d need in Composition > Composition Settings.
We selected the Pen tool in the Tools palette, and enabled the RotoBezier option to ensure smooth curves. We then drew a mask shape directly in the Comp window by clicking along our desired path, in the direction we intend to travel. When the RotoBezier option is checked, mask points don’t have handles as do regular Bezier masks; curves are created automatically to arc between the points you create.
To change the angle of the curve, press the Option key on Mac (Alt key on Windows) and drag your cursor to the left while hovering over a mask point. (For more on editing this flavor of mask paths, search for “rotobezier” in the Help > After Effects Help system.) When done, remember to press V to return to the Selection tool.
If the path has already been created in Photoshop or Illustrator, you can copy and paste the path as a Mask Shape in After Effects. For best results, set the image resolution to 72 ppi in Photoshop so that the size of the path remains the same when you paste, then move it into position as needed. If you are using Illustrator, open Preferences>File Handling & Clipboard and make sure that the AICB option is checked before you copy a path - otherwise it won’t paste into After Effects.
Using the Stroke effect
The first technique involves using the Stroke effect to animate a line tracing the route. This is shown in the MapA-1/setup comp in the accompanying project.
After creating the mask path, apply the Effect > Render > Stroke effect. Stroke draws a colored line along a mask shape (check that the Path popup is set to Mask 1 in the Effect Controls window if you don’t see a white line). Set Color, Brush Size, Brush Hardness, and Spacing to taste (high Spacing values give dotted lines).
To animate the line, turn on the stopwatch for the End parameter in the Stroke effect, and set the first keyframe to have a value of 0%. Then later in time, set the End keyframe to 100%. The line now draws on over time.
If the move is being narrated, the duration as well as any starts and stops will be dictated by the voiceover, but in general, you’ll find a move on a large map takes longer than you might expect. We usually also allow a second of “handle” at the head and tail of the move so that the duration can be extended in the editing stage by duplicating the handle.
The set of comps in the Map B folder show a variation on this technique. We set the Stroke effect to Paint on > Transparent, giving us just the stroke and no background image. We then used a copy of the map as the background; this is Layer 2. This allows us to apply effects such as Bevel Alpha and Drop Shadow to the stroke in Layer 1, as seen in the figure at the top of this page. This variation also demonstrates some starts and stops to match an imaginary voiceover.
Motion Graphics • Post Production •
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