Navmesh Placement Policy - Guide and Use Cases

How the Runtime Spawner integrates with the navmesh system.

Overview

NavMeshPlacementPolicy lets each Spawn Entry decide how tightly it should align to the NavMesh. It removes common pitfalls like off-mesh walkers, and supports streaming/late-baked NavMeshes without stalling gameplay.

The three modes:

1. Require Spawns only after a valid NavMesh point is found. If none is available, the spawner defers the request and retries (exponential backoff) up to Max Deferred Retries.

2. Prefer Spawns immediately and becomes “live” visually, but navigation waits. A lightweight helper enables the NavMeshAgent once the NavMesh becomes available.

3. Ignore Spawns without NavMesh constraints. Great for fliers, physics props, ambient fauna, or scripted placements.

Key fields (per entry)

• Search Radius - how far from the intended position to look for a NavMesh point.

• Area Mask - which NavMesh areas are allowed.

• Max Attempts & Jitter - resiliency knobs while sampling.

• Max Deferred Retries (Require only) - how many backoff cycles to tolerate.

Performance note: sampling is lightweight and gated by attempts/jitter; deferred jobs run on a short tick with a cap to avoid spam.

Interaction with other systems

• Spawn Hints: If a hint has requireNavMesh or overrideAreaMask, those are applied before the entry’s policy kicks in. With Hint Only mode, spawns are skipped if no valid hint qualifies. If your Global Min Spawn Range exceeds a hint’s MaxPlayerDistance, enable Ignore Global Min Distance in Hint Settings or adjust the distances; the locator will warn you in the console.

• Global / Region / Wave: All flows honor the same policy. Waves inherit WaveSpawnPoint anchor tags; the locator prefers hints that match those tags first.

Common scenarios

• Open-world streaming: walkers set to Prefer so enemies appear instantly; their agents enable as tiles stream in. Bosses set to Require to avoid off-mesh intro glitches.

• Procedural arenas: during a rebake, use Require to keep grounded AI off until the mesh stabilizes.

• Flying/swimming units: set to Ignore; no NavMesh dependency.

• Road/bridge areas: use Require with an Area Mask limited to “Road” to keep vehicles from snapping onto sidewalks.

Migration checklist

1. Open each Spawn Entry and choose a NavMesh Placement Policy.

2. For grounded AI, start with Require: Search Radius = 10–20m, Max Attempts = 4–8, Jitter = 0.5–1.5m.

3. If you stream/bake late, consider Prefer for fodder enemies.

4. If using Spawn Hints, verify hint distances vs. your Global Min Spawn Range and enable Ignore Global Min Distance if needed.

FAQ

Q: My walkers never spawn with Require. A: Increase Search Radius, loosen Area Mask, or raise Max Deferred Retries. Ensure a NavMesh actually exists in that area.

Q: Prefer spawns appear but don’t move. A: That’s expected until a valid NavMesh is present; the helper will enable the NavMeshAgent once projection succeeds.

Q: Do waves/regions behave differently? A: No - policy is per entry and applies the same way everywhere. Wave entries simply get their candidate positions from the trigger/anchor.