Record a CARLA simulation

Paths. scripts/… and references/… below are relative to the directory holding this SKILL.md. Your working directory is the user's project, not that directory, so prefix them with its absolute path or the command is not found.

Capture a running simulation to a .log you can replay later (replay-recording) or interrogate (query-recording). The deliverable is a verified log: after stopping, the file is parsed back from the server to confirm it holds frames — start/stop alone confirm nothing.

What it captures: world state per frame — actor create/destroy, transforms, traffic-light states, vehicle wheel/animation and walker bones. With --extra (additional_data) also velocities, accelerations and control inputs. Not captured: sensor output (camera/lidar) — those re-simulate only on replay.

The .log is written on the server's filesystem (see the reference for exactly where).

Instructions

Progress:
- [ ] Step 1: Check prerequisites (bash scripts/check_env.sh), clear FAILs
- [ ] Step 2: Start recording (or use `clip` for a fixed duration)
- [ ] Step 3: Let the simulation run (traffic, scenario, manual drive, ...)
- [ ] Step 4: Stop, then verify the log parses back with frames

Commands need CARLA_HOST/CARLA_PORT from scripts/env.sh. Prefix with source scripts/env.sh or export them.

Step 1: Check prerequisites

bash scripts/check_env.sh

Step 2-4: Record

source scripts/env.sh

# manual bracketing: start, do things, stop
python3 scripts/record.py start --file /tmp/run.log
# ... run traffic / drive / trigger a scenario ...
python3 scripts/record.py stop

# or record a fixed-length clip and auto-verify
python3 scripts/record.py clip --file /tmp/run.log --seconds 20

# capture velocities/controls too (larger file)
python3 scripts/record.py start --file /tmp/run.log --extra

Use an absolute --file so you know where the log lands (a relative name goes under the server's CarlaUE4/Saved/).

Verify

clip verifies automatically; after a manual stop, confirm with the query-recording skill:

python3 ../query-recording/scripts/query.py info --file /tmp/run.log

A valid log shows a frame count and a duration. Zero frames means nothing ran between start and stop, or the path was wrong.

Examples

Example 1: capture a traffic run

User says: "record 30 seconds of traffic"

Start traffic (traffic-manager skill), then clip --file /tmp/traffic.log --seconds 30. VERIFY shows frames + duration ~30s.

Example 2: record around a manual action

User says: "record while I run my scenario"

start --file /tmp/scenario.log, run the scenario, stop, then query info.

Troubleshooting

Problem: log has 0 frames / query says empty Cause: nothing simulated between start and stop, or a bad server-side path. Solution: ensure actors are moving; use an absolute writable server path.

Problem: replayed run has no camera images Cause: the recorder never stores sensor data. Solution: expected — re-attach sensors and replay with --replay-sensors (replay-recording skill) to regenerate them.

Problem: file not found where I expected Cause: relative name resolves on the server, under CarlaUE4/Saved/. Solution: pass an absolute path, and remember it is on the server machine.

Outputs

• A .log recording on the server (path from --file), verified to contain frames. Feed it to replay-recording or query-recording.

Detail (capture contents, file location, size) in references/recorder.md.