Debug the pedestrian navmesh

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.

CARLA does not expose navmesh geometry, but every location from get_random_location_from_navigation() sits on the walkable mesh. Sampling many of them validates the navmesh loaded and visualises its coverage — the check to run after importing a map, or when walkers refuse to move.

Instructions

Progress:
- [ ] Step 1: Check prerequisites (bash scripts/check_env.sh), clear FAILs
- [ ] Step 2: Validate — confirm the navmesh exists and its extent
- [ ] Step 3: (rendered view) Sample + draw to see the walkable area

Commands need CARLA_HOST/CARLA_PORT from scripts/env.sh.

Step 1: Check prerequisites

bash scripts/check_env.sh

Step 2: Validate (works headless)

source scripts/env.sh
python3 scripts/navmesh.py validate --count 500

PASS reports the number of valid points, unique locations, and the walkable span. FAIL (exit 1) means get_random_location_from_navigation() returned nothing — no usable navmesh, so pedestrians with a WalkerAIController will not navigate.

Step 3: Visualise (rendered server)

python3 scripts/navmesh.py sample --count 2000 --life 120

Draws the sampled points via world.debug; the dotted region is walkable. Needs a windowed/packaged server (headless -nullrhi draws nothing — see debug-draw).

Examples

Example 1: after importing a map

User says: "I imported a town — did the pedestrian nav build?"

validate → PASS with a sensible span means yes; FAIL means the nav mesh is missing and must be rebuilt during import.

Example 2: walkers won't move

User says: "my pedestrians just stand still"

validate. If it FAILs, the navmesh is the cause; if it PASSes, look at the WalkerAIController wiring (owned by the walker-spawning skill), not the map.

Example 3: see the walkable area

User says: "show me where pedestrians can walk"

sample --count 3000 --life 180 on a rendered server; inspect the point cloud.

Troubleshooting

Problem: validate FAILs on a freshly imported map Cause: pedestrian navigation was not generated/exported for the map. Solution: rebuild the map's nav mesh in the import pipeline; then re-validate.

Problem: sample prints a count but nothing is visible Cause: headless -nullrhi server, or the camera is far from the coverage bounds. Solution: use a rendered server and move the spectator over the reported bounds.

Problem: very few unique locations Cause: navmesh is tiny or degenerate (a sliver of walkable area). Solution: check the source geometry / sidewalks in the imported map.

Outputs

• validate: a PASS/FAIL report with coverage bounds and walkable span.
• sample: a transient point overlay of the walkable area (rendered view).

Detail (navmesh basics, WalkerAIController link, import checklist) in references/navmesh.md.