David Thorp: Synching Animated Layers in Motion

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David Thorp has a background in visualization and illustration — anything that requires movement and animation. He’s especially good at planning and visualizing how layered animations will work together. We asked him to make a few tutorials using SketchBook Motion, our app for adding movement to static drawings. In this tutorial, he tackles the idea of synching multiple layers of animation. In this animated drawing, his planning makes it possible for him to add flashing lights to a hovering UFO. 

synching animated layers in motion UFO

For this tutorial I wanted to create a simple science-fiction scene with some subtle movement and effects. The challenging effect I wanted to try was to match the behavior with two or even three separate layers. I found an excellent YouTube tutorial from Ninjacrayon outlining the effect and decided to give it a shot. Here’s the end result with movement and flashing lights, which we’ll work toward step by step:


Visualizing Your Layer Stack

The starting point for the animation is the creation of the graphic assets. When building these pieces I like to think of the effects I’m going for and how to organize the layers to help me mask effects I want over and under the image. I kind of build the assets like a sandwich – the bottom piece of bread is the overall image, the meat and cheese are the moving parts and effects, and the top bread is the finishing graphics or final effects. In this case it was a big sandwich. I must be hungry.


A good practice when building your assets is to build in the resolution of the final deliverable or scale it down to match the resolution. For this example I created in SketchBook Motion the resolution is 1024×768 pixels. Additionally, I used a standardized PNG format for all my layers. This format maintains an Alpha channel (this supports transparency) so I don’t have to mask all of my effects.



A Clever Placement Technique

However this does lead to a challenge. The background image is exactly 1024×768, so when I import it to a layer it snaps right in place. However, when I save out a layer like the UFO or some of the other small details there is inevitably a small shift in its position relative to the background.  Now in most cases you can simply move the object into place, but when you want precise placement for an effect there is a strategy I like to use. When I save out my PNG layers I create small square graphics in the upper and lower corners of my 1024 x 768 image. The layer will snap right into place, which I can also visually see with these squares. Once I hit the Place button, I simply erase the squares from the image.


I’ve imported all my layers, added some background effects like a subtle cloud in the distance and some flashing lights, and now I’m going to add movement to the UFO. The effect I’m going for is a slight bobble of the vehicle as it hovers over the landing pad, but I also want some flashing lights that will stay in line with the UFO. I’ve created the graphic of the UFO with Alpha channel holes in the image for the lights to shine through. Now I just need to create the effect. Currently SketchBook Motion doesn’t allow nesting or copying behaviors, but there is a way to do it.

Step 1: Creating an anchor layer with Beeline movement

Start with the movement of the UFO. I created a very small Beeline movement of the UFO and set the Path speed to a very slow setting. I had to make sure I was happy with the movement of the vehicle before I moved on to the next step because there is no way to change the settings once you move to step two.


Step 2: Duplicating layers on the same path

Now that I have the movement I like I duplicate the UFO layer by simply pressing the Duplicate button in the layer flyout menu.


The duplicate UFO layer will appear at the top of your layer stack so drag the layer below the original UFO layer to keep things tidy. You’ll notice the animation of the two layers is different. They have the same behavior and the same speed, but the objects are not in the same place on their path. We need them to be synchronized for this to work so start by hitting the Pause button in the upper right-hand screen of SketchBook Motion to freeze the animation.

Next, to get both layers synchronized select the first UFO and press the Path button. This will place the layer in its starting position on the path. Next, select the second UFO and press the Path button. This layer will also return to its starting position, and now when you un-pause the animation it will look like there is only one UFO. They are synched up perfectly.

Step 3: Erasing a layer but keeping its path

We don’t need two layers with the UFO, only the top layer. The bottom layer is going to be my flashing lights so I start by Pausing the animation again, turning off the top layer, and erasing all of the UFO details from the bottom layer. Everything is gone from the layer now except for the behavior. Turn the top UFO layer back on, make sure to activate the now-empty UFO layer, and use SketchBook Motion to paint in white under the holes in the graphic. It’s a good idea to test the animation to make sure the white is lining up correctly. At times the paths might lose their synchronization so simply pause and press the path buttons for each layer to get them back on the right track.

One way to animate is by hiding or “flashing” layers on and off. Here, our spaceship’s Opacity is completely turned off.

Step 4: Creating a strobe effect by turning Opacity on/off

To make the lights flash we’ll need one more layer to sit behind the white layer so repeat step 2 and 3. Duplicate the white layer, move the duplicate layer down in the stack under the white layer, synchronize the animation paths, erase away the white and paint in black. Finally, we need a simple modification on the white layer to get it to flash so select the white layer, open up the behavior controls, and expand the advanced controls and add a jagged path to the Opacity control to get the layer to turn on and off.


There you have it! It’s a bit on the complicated side, but I expected some difficulty with this challenge. Experiment with layer placement and opacity controls to get this kind of more advanced effect to work for you, too.