Phases and events — how scenario logic is structured

The LOGIC card at the bottom of the screen is where a scenario’s behaviour lives. This page explains what its parts are and in what order they run.

The four levels

The graph nests four things, outermost first.

Level	What it is	OpenSCENARIO
Phase	A named container with a Start condition.	Act
Actor row	One row per entity taking part in the phase.	ManeuverGroup (its entityRef)
Event	One trigger plus one or more actions.	Event
END CONDITIONS	The node at the end of the graph. Decides when the run stops.	the storyboard’s StopTrigger

Phases

Click + Phase to add one. The button is disabled until the scenario has at least one actor — its tooltip says Add an actor first.

A new phase does not arrive empty. One click produces Phase 1, an actor row for your entity, and Event_1 carrying a default Change Speed action and a default Simulation time trigger. The event editor opens on the right at the same time.

Imported scenarios keep the original act names, so a phase may be called something like CutInAndBrakeAct rather than Phase 1.

The Start row

Every phase has a Start row with three options:

Option	Meaning
At scenario start	The phase becomes active as soon as the run begins.
After a delay…	The phase becomes active a fixed number of seconds into the run.
Custom…	Any trigger condition — the same catalogue used for event triggers.

A phase’s Start condition is independent of the phases drawn above it. Two phases both set to At scenario start both become active at t=0. Sequencing comes from the Start conditions you set, not from the vertical order of the cards.

Deleting a phase

The small × on a phase card deletes it, along with every event, action, and trigger inside it — with no confirmation prompt. Undo it with Ctrl+Z or the ↶ button in the toolbar.

Right-clicking a phase gives you Add Event (actor) and Delete Phase.

Events

An event is the unit of behaviour: one trigger, one or more actions, applied to one actor.

Add one with + Event in the actor’s row. Each new event arrives with the same defaults as the first — a Change Speed action and a Simulation time trigger at 0.00 s. Two events left at 0.00 s fire simultaneously, so set the trigger before you move on.

Reading an event card

Each card carries two lines:

• Top line — the event name, the simulation time at which it fired (t=2.05s), and a ✓ once it has completed.
• Bottom line — a summary of the action, for example 8.3 m/s · over 2 s, 1 → · over 30 m, same lane as Ego · over 3 s, or parallel 0 m/s · @-4 m/s².

The fire time and the check mark are filled in during playback, so the graph doubles as a run log.

The event editor

Selecting a card opens the editor at the top right, headed actor › event.

Section	What it holds
ACTOR	The entity the event acts on.
TRIGGER	One or more conditions, grouped. See Triggers.
ACTION	What happens when the trigger fires. See Actions.
+ Action	Adds another action to the same event — they all run when the trigger fires.
ADVANCED	The attributes below.

ADVANCED

Field	Options	OpenSCENARIO
PROFILE	Linear / Cubic / Sinusoidal / Step	dynamicsShape
PRIORITY	Auto / overwrite / parallel / skip	Event@priority
REPEAT (EVENT)	how many times the event repeats	Event@maximumExecutionCount
REPEAT (GROUP)	how many times the actor’s group repeats	ManeuverGroup@maximumExecutionCount
MANEUVER	the maneuver name the event belongs to	Maneuver@name
DELAY AFTER MET	seconds to wait after the trigger is satisfied	Condition@delay

PRIORITY decides what happens when this event fires while another event is still running on the same actor: overwrite stops the running one, parallel lets both continue, and skip drops the new one. Auto lets drawtonomy pick.

MANEUVER exists mostly for round-tripping. drawtonomy does not draw maneuvers or maneuver groups as separate boxes, but it preserves their names so an imported scenario exports with the same structure.

What runs when

1. The run starts. Every phase whose Start condition is already satisfied becomes active.
2. Inside an active phase, each event evaluates its TRIGGER every step. When the trigger is satisfied — plus any DELAY AFTER MET — the event’s actions start.
3. Actions run to completion according to their DYNAMICS (over a time, over a distance, or at a rate).
4. The run stops when the END CONDITIONS node is satisfied. Left on Automatic, that means “when everything has finished”.
5. If a FAIL CONDITION triggers at any point, the run ends with a FAIL verdict instead.

See End and fail conditions for steps 4 and 5.

Variables and parameters

The {x} button on the LOGIC card opens the PARAMETERS and VARIABLES panel — OpenSCENARIO’s ParameterDeclarations and VariableDeclarations. Parameters are fixed at the start of a run; variables can be changed during one with the Set Variable and Modify Variable actions.

One caveat, stated in the panel itself: editing a parameter does not retroactively change actions that were imported with a literal value, because parameter references are resolved at import time.

See also

• Actions reference
• Triggers reference
• End and fail conditions
• RoadRunner and OpenSCENARIO terms