Working with Entity Actions

We can use Entity Actions in Timelines to animate changes to our scenes.

Overview

Timelines in RealityKit are a feature of Reality Composer Pro. Understanding timelines means learning three concepts

1. Behaviors trigger a timeline. See Working with Behaviors for a breakdown of the options.
2. Timelines are containers for one or more Entity Actions. See Working with Timelines.
3. Entity Actions can update entity components.

Today we’ll dive into Entity Actions. These actions make up the content of our Timelines. You can find a list of available actions in the right side of the Timelines editor in Reality Composer Pro.

Simply drag an Action into a timeline to get started. You can edit the properties/options for an action using the inspector. For example, here we have selected the Spin action. Notice that the inspector is populated with options for that action. It even provides helpful tips. In this case we are trying to use an action that requires an Opacity Component, but our entity doesn’t have one.

Just like in the rest of RealityKit, we don’t edit Entities directly. We adjust data on components for entities. Actions are no different. The Show and Hide actions animate the opacity value of the Opacity Component. The Transform To and Transform By actions update the Transform Component.

Options vary, but each action generally needs to target an entity. The actions in our EarthActions Timeline all target the Earth entity in our current scene.

Some actions provide a visual preview of their effect in the scene. For example, this Orbit action shows us the path that the Moon will take around the Earth. Notice that this action targets the Moon entity and has a section value called Pivot Entity that targets the Earth.

We have access to simple actions like Spin, Orbit, Show, Hide, Enable, Disable, and Emphasize. Then there are actions that do a bit more such as playing audio or animations configured on an Entity. There are even a few advanced actions. For example, we can broadcast notifications, change the timeline that runs for a given behavior, or apply physics forces. We encourage you to explore each of these, but let us know if you would like to see any of these in more detail.

Something to keep in mind: We can also use these Entity Actions in code. See also:

• RealityKit Basics: Perform Entity Actions
• Entity actions documentation

Download the Xcode project with this and many more examples from Step Into Vision.

Some examples are provided as standalone Xcode projects. You can find those here.