Amazon Sumerian
User Guide

Logic and Transition State Machine Actions in Amazon Sumerian

You can use state machine actions in Amazon Sumerian to run scripts, respond to events, and add transitions to a state.

Logic actions perform calculations, run scripts, or interact with the page document.

Logic Actions

  • DOM listen – Add a DOM event listener on one or many elements (specified by a query selector), and perform a transition on a given event.

  • Emit message – Emit a message (a ping) to a channel on the bus. Messages can be listened to by the Listen transition action, or by scripts using the SystemBus.addListener(channel, callback) function.

  • Execute script – Run a script, and transition on success or failure. Use the enter and exit functions in your script to run code when the state is entered and exited. To trigger a transition, call ctx.transitions.success() or ctx.transitions.failure() on the context object.

  • Execute script condition – Evaluate an expression, and transition on a true or false result.

  • Execute script expression – Execute a statement.

  • Get HTML text and Set HTML text – Read or change the contents of an HTML element.

  • Log message – Print a message in the debug console of your browser.

  • Toggle full screen – Expand the scene to fill the screen. For browsers to allow this, the previous state must have a Click or tap on entity action that transitions to the state that runs this action.

Timeline actions interact with the entity's timeline component.

Timeline Actions

  • Pause timeline – Pause a timeline.

  • Set timelime time – Jump to a point on a timeline.

  • Start timeline and Stop timeline – Start or stop a timeline.

Transition actions move from one state to another. Many actions include transitions. Use transition actions if the actions on a state don't include one, or to add branching behavior to your state machine.

Transition Actions

  • In view – Perform a transition based on whether the entity is in a camera's frustum.

  • Listen – Perform a transition on receiving a system bus message on a channel.

  • Random transition – Perform a random transition.

  • Transition – Transition to a different state.

  • Transition on next frame – Transition to a selected state on the next frame.

  • Wait – Perform a transition after a specified amount of time, or a random amount of time between 0 seconds and a specified maximum number of seconds.