Cut Lines: Writing Lines onto the Screen with Apple Motion
Posted Nov 30, 2010

This month I’ll show you one of Motion’s more popular Behaviors, Write On. Basically, it lets you draw a line, then have that line “write” onto the screen, as if you were drawing it live with a pen. This can be really artistic if you use this technique with a Wacom. I’ll show you the ins and outs of how this trick works and how to manipulate it. It’s really quick and easy to do, and it can be lots of fun.

There are two methods for drawing these lines, so in the first example we’ll use the Bezier tool to have a very simple line drawn to show the flight paths of a trip on a map. In the second example we’ll work with a simple introductory title where a line will draw itself around some elements in the frame. An important thing to bear in mind is that even though we have two different tools to draw these lines, once drawn and tweaked, we’ll switch back to the regular Arrow tool, and then they are both just a simple Shape object. Thus, manipulating it from then on is the same—two paths to the same goal.

Working with the Bezier Line Tool
We’ll start with a Motion project that already has a map on it and the image of a plane animated across it. I want a line to follow the plane on its journey. This will add a step of complexity with this specific project, but I want to show how easy it can be to follow up on something already created.

To begin, select the Bezier tool from the toolbar. It’s the second tool in the Create section of tools (Figure 1, below). Then, play through the timeline, using the spacebar to start/stop play and the left/right arrow tools to move a frame at a time to find just the right spot.

Apple Motion
Figure 1. Motion's Create section of tools

At each of the airplane’s waypoints, you’d click with the Bezier tool to create a Bezier point (Figure 2, below). Once all my points are made, you can click on each to make it a Linear (straight line with hard angle at the point) or Smooth (with handles to round out the points). Then you can hit F7 to bring up the HUD to make some minor adjustments. Be sure to uncheck Fill and check Outline. Note that the Roundness control in the HUD will help smooth out the Bezier points even more. F4 will bring up the Shape tab in the Inspector pane for more control. For my example here, I want hard corners, so we’ll leave them all as Linear points.

Apple Motion
Figure 2. Creating a bezier point on the map

When done, click the arrow tool (Shift+S) in the toolbar, and your Bezier line becomes a shape object. Now with this new Bezier layer highlighted in my Layers pane (F5), the first thing you want to do is to look at the timeline. Be sure your Bezier layer starts and ends where it needs to (F5) by grabbing and dragging the beginning and end left or right, or by grabbing its center to move the whole layer left or right. This is the same technique you’d use with clips in FCP’s timeline.

Next, go to the Behaviors button in the toolbar, go to the Shape group, and choose Write On (Figure 3, below)

Apple Motion
Figure 3. Choosing the Write On effect from the Shape group

Be sure the Bezier and its Write On layers begin and end in the Timeline where you need them. This controls the speed of the Write On effect (Figure 4, below). In the Shape tab (F4) of the Inspector you can control the thickness and color of the line being drawn. That’s all there is to it.

Apple Motion
Figure 4. Controlling the speed of the Write On effect in the Timeline

Writing on the Screen with the Paint Stroke Tool
Doing this same technique with the Paint Stroke tool is very similar, but you can also use a Wacom tablet with this method, which helps if you want to hand write text or add more of an artistic flourish.

With the opening title screen, we’re going to make a more artistic, animated, drawn-on line using the Paint Stroke tool. It is right next to the Bezier tool in the toolbar, or you can hit the P key. With the playhead where you want the line to start drawing in the timeline, simply click and drag to draw your rough line. This will create a layer called Paint Stroke. The first thing you want to do in the timeline is make sure your Paint Stroke layer starts and ends where it needs to (F6) by grabbing and dragging the beginning and end left or right, or by grabbing its center to move the whole layer left or right, as we did before.

As before, with your Paint Stroke layer highlighted you can use the Heads-Up Display (HUD; F7) or the Shape tab of the Inspector pane (F4) to make some adjustments. Be sure that the Fill box is unchecked and the Outline box is checked. Again, the Roundness control will smooth out your rough line. Now comes the fun part: At the bottom of the HUD, or the top of the Shape tab, click the drop-down menu for the Shape Style parameter (Figure 5, below). Experiment with some of these if you wish. The drawback here is your speed is not really controllable. Note that this option is only available if the Brush Type is Airbrush, which I’m about to point out.

Apple Motion
Figure 5. Choosing a Shape Style

The Final Shape Object
If you have that Airbrush line animating from the Paint Stroke, you can always go to the Shape tab and set the Brush Type in the Outline section to Solid. Then you can add the Write On behavior as we did with the Bezier line and work with this Paint Stroke the same way as before. This is also available with the Bezier tool, being able to switch back and forth from Airbrush and Solid brush types. But bear in mind that when you draw a line with either tool, once you switch back to the Arrow tool, they are both just a Shape object. Everything works the same from that point forward. Thus, you have two ways of drawing the original line, but once you’re done, the line is simply a Shape object and can be manipulated the same ways.

You may want to experiment with lines of different characteristics, moving along different paths. Make a Group called Animated Lines, and put all of your Shape objects created with these techniques in it. Then do a few different lines to experiment. By checking and unchecking the boxes to the left of each shape layer, you can turn each one on and off. This allows you to make more than one, experiment with each, finally settling on the one you like the best. Play with this technique a bit, experiment, and you’ll find learning it is quick, using it is easy, and you’ll have a lot of fun. Also look at the other panes of the Shape tab (Style, Stroke, Advanced, Geometry). Then Duplicate (highlight, Cmd+D) a layer before continuing. Explore the panes as you wish; experiment, remembering that Shift-Z is Undo; and have fun!

I normally bring these effects directly into my FCP projects as Motion project files. It may take longer to render out, but I can always tweak them easily in Motion as I need. You can always export your work as a QuickTime movie file, so there’s no rendering in FCP. Use the roundtrip method that works best for you.

You can see the final versions of these two examples on bbalser.com. I hope you find some use for these techniques and have a lot of fun experimenting with them. As always, until next month, rock those edits!

Ben Balser (benb at bbalser.com) is an Apple Certified Master Trainer and Support Professional based in Louisiana. He produces media, consults for studios, and teaches media production nationally.