Form
In this specific context, a form is a shape along which particles are arranged. Let's illustrate this with the Magic Torus preset. The preset's default design (shown below) is comprised of three forms: Primary Form, Form 2, and Form 3. Form 2 is the texture of speckles that loosely fill the ring's shape. As you can see, those specks are actually Sphere particles, as defined by the Particle Type F2 parameter. The end result is a ring-shaped form of tiny Sphere particles.
If we change Particle Type F2 to Textured Polygon and select 6-pt Star for the sprite (and maybe tweak a few other controls to make the change clearer), we get this:
On this page, we’ll examine working with multiple forms — how to set them up and how to work with them in the Form UI within After Effects' ECP. Note that it’s usually best to work with multiple forms in the Designer. For more information on this, consult the Multiple Forms in the Designer page.
At the top of the Form interface, you’ll find a Show Forms area. This is where you can create a new form or select which of your forms to adjust. You can create up to seven additional forms (eight forms total).
To create a new form, click the Add a Form button. This will launch the Designer, in which you can start with the Presets Pane to create a new form. Upon accepting your changes in the Designer (by pressing Apply in the bottom-right corner) and coming back to the Form UI, you’ll see the form selectors in the Show Form area populated with the new form. You’ll also see significantly fewer options in the ECP.
After creating a new form, Form only shows you the parameters for that specific form by default. The name of the form you are adjusting is seen in the name of the properties. For example, selecting “Form 3” reveals all of the parameters for Base Form 3, as shown below.
Note how the form selector of the selected form is a little brighter in the Show Form area to indicate which form you are currently adjusting. Since forms typically use very similar sets of parameters, it's important to keep track of which form you’re working on so as not to mistakenly alter the wrong one.
To change forms, simply click a different form selector button in the Show Form area. The Form UI updates to show you properties for the form you’ve selected.
Note that additional forms only have two groups by default: Base Form and Particle. More groups and properties can be added in the Designer, but they are initially turned off by default. This is discussed below in Adding Properties to Forms and much more in depth on the Multiple Forms in the Designer page.
To show all forms, click the All Forms button at the bottom of the Show Forms area.
Hiding Forms
In addition to being able to clean up the Form UI to focus on a certain form, you can likewise hide forms from the Composition panel.
Soloing Forms
To “solo” a form (meaning you only see that form), you have two options. You can Alt/Opt + click the eye icon to solo a form. You can also click on the pop-up menu on the form selector’s right side and choose Solo Form.
Note that when a form is soloed, a golden circle will outline it.
From this same form selector pop-up menu, you can also choose Unhide All Forms to show all forms in the Composition panel. This is different than the All Forms button in the Show Forms area, which shows the adjustable properties of all forms in the Effect Controls panel.
Alternatively, you can click any eye icon to turn off soloing.
Deleting Forms
To delete a form, choose Delete Form from the form selector pop-up menu.
Resetting Forms
To reset a form back to its defaults, choose Reset Form from the form selector pop-up menu.
Adding Properties to Forms
Form only gives newly created forms a limited range of properties from the Base Form and Particle groups. Giving access to only the most commonly used features helps keep the ECP tidy. However, if you’d like more power, the Designer offers power in spades.
Inherited Values
You can also use the Designer to have a secondary form (i.e., non-primary forms) inherit attributes from the primary form. This creates a relationship between the primary form and selected attributes of the secondary form. Then, when you change a primary form attribute, that change ripples down to all secondary forms that inherit those values.