Be still my beating heart!
Or if you can’t be still, let me see how you beat! That’s our subject for this week’s Motion Magic, in which I demonstrate one way to build an animated heartbeat monitor.
I created the heartbeat pattern using the Bezier tool to draw a Motion Paint Stroke layer. Now, experienced Motion users may wonder why I didn’t use the Write On behavior to animate the paint stroke onto and off the screen – after all, it’s very simple and intuitive to use. The problem is in the timing of the animation. You see, with a heartbeat monitor, the line is drawn at a constant horizontal velocity: this means when the line goes up or down, it must go much faster then when it is moving horizontally in order to maintain a consistent horizontal speed. While that could be accomplished by keyframing the write-on behavior (after setting it to Custom), I felt that animating a mask would be a much easier approach.
I take advantage of Motion’s Image Mask, which lets you mask any layer or group of layers with any other layer or group of layers. I find it much more flexible than a traditional travel matte because the layers don’t need to be right next to each other.
By animating an opacity gradient across the paint stroke with a couple of keyframes and using it as the image mask source, you can quickly set up the basic animation. Creating the light ball at the head of the path involves creating a copy of the same basic paint stroke and mask combination with a few adjustments to make the light brighter and larger.
By animating the group containing the mask sources, any new masks are automatically animated and perfectly match the current animation. Check out the under five minute video for all the details.