Skip to content

AcresSimControl.h#

Acres/Source/Acres/AcresSimControl.h Generated

Simulator control: the session-wide channel the ROS 2 side (ROS/acres_sim) and learners use to pause, play and step the world in lockstep, reset it, move and spawn entities, change the conditions and the vehicles' hardware shifts, record the episode log and replay one. Protocol: Documentation/Reference/sim-control.md (newline-delimited JSON on 127.0.0.1, -SimControl=<port>); episode log: Documentation/Reference/episode-log.md.

-SimControl=<port>          the control channel
-Lockstep                   start held: the world advances only on step requests
-EpisodeLog=<file.mcap>     record the episode log from the first physics step
-EpisodeReplay=<file.mcap>  replay an episode log (the agents follow their logged poses; -EpisodeReplayExit
                            quits when it ends)

Agent 0 (the game mode's pawn) creates the one instance at the end of its BeginPlay when any of these flags is given, after it spawned the other agents, and deletes it in EndPlay.

Lockstep: a step request switches the engine to a fixed frame time of exactly one physics step (FApp fixed time step at the async physics step, 1/120 s: the Chaos solver then runs exactly one step per frame), releases the world (AWorldSettings pauser cleared) for N frames and holds it again (pauser set) before the next frame's world tick. While held, the world does not tick (no physics, game time, NPC or timer), but frames keep rendering and the vehicle pawns keep ticking (bTickEvenWhenPaused): their sensors finish the scans and images that fell due and their bridges flush reports. The reply is sent when the physics has done N steps and every agent's sensors are idle, after a barrier went into each connected sensor stream and RL bridge.

Threads: everything runs on the game thread (FWorldDelegates::OnWorldTickStart for the socket and the step scheduling, FCoreDelegates::OnEndFrame for completion, recording and replay bookkeeping) except RecordStep and ReplayState, which the pawns call from their physics steps.

FAcresSimControl#

Opens the channel and the log or replay the command line asks for.

Argument Description
InAgent0 The session's agent 0 (the game mode's pawn); must outlive this object. 
explicit FAcresSimControl(AAcresVehiclePawn* InAgent0);

~FAcresSimControl#

Closes the socket and the episode log, restores the engine's frame timing.

~FAcresSimControl();

Get#

The session's instance, or null. Game thread (and the pawns' physics steps, which only use the thread-safe members).

static FAcresSimControl* Get() ;

IsRequested#

True when the command line asks for simulator control (any of the flags above).

static bool IsRequested();

IsLockstep#

True while the world is in lockstep (held or stepping): the RL bridge then does not brake a client that is slow in wall-clock time.

static bool IsLockstep() ;

RecordStep#

Physics thread, end of every agent's step: queues the agent's state for the episode log. Cheap when not recording.

Argument Description
Agent The pawn.
State Its episode-log state after the step (base_footprint pose in the world frame, ...).
WorldTimeS World time of the step, s. 
void RecordStep(const AAcresVehiclePawn& Agent, AcresLog::FAgentState&& State, double WorldTimeS);

IsRecording#

True while an episode log is being recorded. Any thread.

bool IsRecording() const ;

IsReplaying#

True while an episode log is being replayed (the pawns then follow it instead of simulating).

bool IsReplaying() const ;

ReplayState#

Physics thread: the logged state of an agent at a replay step.

Argument Description
AgentName The agent's name.
ReplayStep Physics steps since the replay started (0 = the first logged step).
Out The logged state (the last one once the log has ended).
OutWorldTimeS The logged world time of that step, s.

Returns: False when the log has no such agent.

bool ReplayState(const FString& AgentName, uint64 ReplayStep, AcresLog::FAgentState& Out, double& OutWorldTimeS) const;