8
The Expression Controls Effects
The Expression Controls category of effects contains what is perhaps the most odd group of effects. Other than the effects in the Audio category, most effects make some kind of visual change. The Expression Controls effects are used to control expressions, which are used to control the values of layer properties. In effect, they control the controllers.
One of the big limitations of expressions is that they cannot be animated. Let’s say you wanted to simulate an earthquake by applying a Wiggle expression to the Point of Interest value on your camera layer. Once you applied the expression, the wiggling would last for the entire duration of the layer (or, the composition, whichever ended first). Enter the Expression Controls effects, which can be used in conjunction with expressions to create animations. In this case, we could create a null layer and apply the camera controlling expression control effect to the null. As we’ll also see, these Expression Control effects can also used simply as a visual controller for expressions, to make them easier to work with.
Because all of the Expression Controls effects are applied and function in a similar manner, let’s take a look at how expressions can be controlled with them. Then we’ll look briefly at what each Expression Controls effect can be used for.
Create a new After Effects project, then a new composition at the NSTC DV size. Then create a new solid (any color) at the comp size. Go to the Animation menu at the top of the interface and select Apply Animation Preset. Navigate to the Animation Presets folder in the exercise files that came with this book, and select the chads fire—campfire.ffx preset. This is a simple fire pattern created with the Fractal Noise effect (Chapter 12) and colored with Colorama (Chapter 6).
In the Timeline panel, select the solid layer and press UU (that’s the letter U two times fast). This will reveal all of the properties that have been altered from their default settings.
Figure 8.1
The chads fire—campfire animation preset.
Look for the Effects>Fractal Noise>Brightness property. Hold the Alt(Win)/Opt(Mac) key and click the stopwatch for the Brightness property. A text field will open up in the Timeline panel for you to type in an expression. Completely replacing all existing text in this area, type wiggle(5,10). This will create random brightness values within 10 units of the existing value for the Brightness property 5 times every second. This will create an organic flicker of brightness.
So, the results look great, but what if we wanted to increase the intensity of the flicker over time? For this, we must turn to expression controls.
Apply the Slider Control effect (in the Expression Controls area) to this solid layer. Click in your expression once again to make the text editable. Then, as if in a text editing application like Microsoft Word, click and drag to highlight (select) the second number, 10.
With the number 10 selected, click and drag the pickwhip in the Timeline panel to the Slider property of the Slider Control in the Effect Controls panel, and release the mouse.
Figure 8.4
With the number selected, click and drag the pickwhip to the Slider property in the Effect Controls panel.
Now, the Slider value of the Slider Control effect is controlling the amount of variation in the brightness wiggle. We can set keyframes (or even other expressions!) to control the Wiggle expression, because of the Expression Controller effect we’ve added here.
Naming Effects
If you plan on using Expression Control effects, it’s a really good idea to rename the effect so you can instantly discern which property it is controlling.
As you can probably tell, there’s really nothing special about this Slider Control effect. It’s just a slider that does nothing. It really doesn’t serve any other purpose, other than to control other behaviors in After Effects.
This example demonstrated a simple effect with one simple Slider parameter. But what if you wanted to control the Evolution property in Fractal Noise, or rotation, or some other property that uses revolutions and degrees? A simple slider wouldn’t be the best controller in that case. For that purpose, you’d need a controller that used revolutions and degrees. And this is why there are several effects in the Expression Controls category. Let’s take a glance at the nature and purpose of each controller, as well as a few examples of them in action in real world projects.
The Angle Control Effect
The Angle Control effect is for controlling properties with angle controls. It has degrees, and can keep track of the number of complete revolutions.
Figure 8.5
The angle control effect.
The Checkbox Control Effect
The Checkbox Control effect is for controlling effects with an on/off switch, such as Invert.
Figure 8.6
The checkbox control effect
I recently used this on a really fun project—a tutorial for Red Giant TV (which can be found for free at redgiantsoftware.com/videos). The tutorial was actually about 3D in After Effects, but I created this theme of a vintage Twilight Zone show opening as my design motif.
Figure 8.7
An end frame of my Red Giant TV tutorial.
At the end of the tutorial, I showed the final text, but I also wanted creepy, sudden flashes of cracked text to interrupt the calm final text display.
Figure 8.8
A figure of the cracked “interruption” text.
So, I created an adjustment layer with the Checkbox Control effect applied. Then animated the Checkbox property to be mostly off, then occasionally turn on. Then (and here’s the key), on the Opacity property of the shattered version of the logo, I applied this expression:
In more simple terms, this expression says that if the Checkbox is off (0), then the opacity of the shattered text is 0% (which is off, essentially). The next line says that if the Checkbox is on (1), then the opacity of that layer is 100%. On the regular text layer, I simply reversed this, telling it be be 100% opaque when the Checkbox is set to 0 and completely transparent when it’s set to 1.
That basically turned the Checkbox slider into an on/off switch (and an off/on switch) for these two layers. And this is the power of expression controls in a nutshell. We can control all kinds of stuff with just one checkbox or slider or what have you.
Another detail here is that I also created an Adjustment layer at the top of the layer stack here, and applied a Glow effect, a Levels correction, and a Transform effect with a Wiggle expression on the Position property. I applied the same expression as above to its Opacity value as well. So, once I clicked the Checkbox on, not only did the shattered version of the logo turn on, but it also was brighter, had glow, and shook a bit.
The Color Control Effect
The Color Control effect allows you to select and animate the color change of a color swatch. This can be used to control the change the color of multiple properties at once.
Figure 8.9
The Color Control effect.
The Layer Control Effect
The Layer Control effect is a unique effect in a group of unique effects. The Layer Control effect only gives you the option to select a layer. That’s it. It’s the only Expression Control effect that doesn’t animate.
Because it doesn’t have the capacity to animate, the Layer Control effect can’t be used as the “standard” expression controller. Use the Layer Control effect when you need to swap several layer-controlled parameters at once. Let’s say that you’re using the powerful Caustics effect which has many parameters that are controlled by other layers. Additionally, you may add to this other effects (such as Colorama) which can also be controlled by other layers. If you change one of the map values, you may want all of the other properties that use this map to change as well. You could use the Layer Control effect to make the change so that all properties connected to this controller change to the new layer as well. It’s not something that your viewing audience will ever see, but it can help you work more efficiently.
Figure 8.10
The Layer Control effect.
The Point Control Effect
The Point Control effect is for controlling properties with an effect point control. These are usually properties with X and Y position values.
The Slider Control Effect
The Slider Control effect is perhaps the most useful of the Expression Control effects, probably because most properties in After Effects work like the Slider effect works. It simply adjusts (and allows you to animate) from one value to another. But, as noted in the example earlier in this chapter, it is extremely helpful in its simplicity.
Figure 8.12
The Slider Control effect.
Let’s take a look at this effect in use in a real project. I recently created this monster arm for use in a promotional intro for tutorials on my blog, Movies & Computers (moviesandcomputers.com).
Moments later in the animation, this monster hand swoops down and grabs the camera away from the unsuspecting director.
I knew that I wanted this animation, but I also wanted the flexibility to control this complex rig easily. There are, after all, 13 different shape layers here, and once things are animated, it would be a complete and total mess trying to change things. So, to help me keep from pulling my hair out on this project, I created a “rig” of this arm and hand. I used a Slider effect to control everything, and it actually makes this fun to play with.
In the Slider.aep project in the Chapter 8 folder of the exercise files, you’ll find the Rigged Arm START comp. This contains the 13 pieces used to make the monster arm. I’ve gone ahead
Figure 8.14
YOINK!
and parented them all up for you. But even with these parenting relationships, it would still be a bother to animate.
So, let’s set this up RIGHT. Create a new adjustment layer and name it ARM CONTROLLER (or whatever you want). Apply the Slider effect to the adjustment layer, and in the Timeline panel, expose the Slider value of the Slider effect.
Then, on each of the visible layers (except for palm, forearm, and upper arm), (AltWin)/Opt(Mac)+click on the stopwatch for the Rotation property, and then drag the newly created pickwhip to the Slider property of the Slider effect on the ARM CONTROLLER adjustment layer. That creates a simple expression that allows the Slider value to control the rotation property of each of these layers. Figure 8.15 shows this process in action.
Figure 8.15
This process in action.
With that done, the Slider control now rotates all of these layers at once. Take the Slider value to 20 for example, and all of the fingers move!
Figure 8.16
The fingers move in the same direction, controlled by the expression control.
This is cool, but we don’t want them all to rotate in the same direction. What about opposable thumbs? How could Darth Vader air-strangle people without those? So, we need to modify some of these expressions slightly. On the thumb layers (called “thumb 1” and “thumb 2”), click in the expression in the Timeline panel and add *–1 to the end of the expression. This will multiply the Slider value by negative 1, making the thumb layers rotate in the opposite direction as the rest of the fingers.
Figure 8.17
After correcting the expressions on the thumb components, the thumbs are opposable, allowing you to grab as desired. Shown here with a Slider value of –31.
If you want to, you can also add another couple slider controls to the adjustment layer and link each with an expression to the forearm and upper arm rotation values. You can then click the name of the Slider effect and press the Enter/Return key to create new names for these Slider effects (e.g., grip control, elbow control, etc.). This took a couple minutes to set up, but it’s now so flexible and easy to adjust, not to mention loads of fun.