NAV_MESH_AVOID annotation penalizes bot path costs - #2170

Description

Bots route around NAV_MESH_AVOID areas

NAV_MESH_AVOID is the stock nav attribute for "avoid this area unless alternatives are too dangerous" (nav.h), set with nav_avoid in the nav editor. Today it means nothing to NT;RE bots: CNEOBotPathCost ignores it, so a mesh author has no way to steer bots away from a problematic spot short of cutting it out of the mesh.

With this PR a step into an AVOID area costs 20 times its cost (neo_bot_path_penalty_avoid_multiplier). Bots route around such an area wherever a reasonable alternative exists. The cost stays finite, so an AVOID area that is the only way somewhere is still used. A ladder crossing pays the multiplier when either end is AVOID, so a risky ladder can be discouraged by marking its foot, not only its top.

One file, neo_bot_path_cost.cpp, +13.

Navmesh PRs that rely on this

These navmesh PRs mark NAV_MESH_AVOID areas and are reviewed and merged after this one. Without it each mesh still loads and works; the marks are ignored.

• ntre_ridgeline_ctg: navmesh rework and hillside ladder neoAssets#143 (ntre_ridgeline_ctg): the tower-base strip (area 16274), a 25 u strip between handrails and a power-line tower base where most bot visits stalled.
• ntre_tarmac_ctg: navmesh rework neoAssets#149 (ntre_tarmac_ctg): the parapet top (3489, 3496), which Recons otherwise take to ghost spawn 7, and ladder 2's foot (885).
• ntre_apparatus_dm: first navmesh neoAssets#157 (ntre_apparatus_dm): ladder 13's foot (5374) and the blast-door frame top (8604), where bots stalled under a ceiling beam.
• ntre_rise_ctg: navmesh rework neoAssets#160 (ntre_rise_ctg): 89 areas, the basement pool, the balcony rail top above it and ladder 1's foot room.

These also mark NAV_MESH_AVOID areas and were measured only on a build that carries this PR: NeotokyoRebuild/neoAssets#161 (ntre_threadplate_ctg, the crouch-duct pocket), #162 (ntre_sentinel_ctg) and #165 (ntre_sentinel_jgr, the elevator pits and walkway slivers), #164 (ntre_skyline_ctg, ladder 1's foot).

Why a path cost, not removing the area

Cutting an area out of the mesh also removes the only route when nothing else reaches that place, and bots then cannot follow a player or an objective there at all. A cost keeps the route for when it is needed and lets the mesh say "not this way if you have a choice".

Where it applies

No mesh on master carries NAV_MESH_AVOID today. It ships with its first users, the navmesh PRs above. Ridgeline (NeotokyoRebuild/neoAssets#143) marks one area: a 25 u strip between handrails and a power-line tower base where most bot visits stalled. Bots rarely route there at all, so ridgeline shows the mark working rather than a large effect. The measurable effect is on maps whose meshes will mark busier spots. On the research meshes there are 19 AVOID areas on 7 maps:

• sentinel ctg / jgr: the floor at the foot of the two restored ladder shafts
• skyline: a ladder foot
• rise, ridgeline, apparatus, threadplate: pockets, stall spots and ladder ends

Evidence

Bot matches with the research meshes, 30 bots, default weapon damage, CTG with the ghost pinned at 3 spawns (JGR: the juggernaut; DM: unpinned), both arms interleaved in one batch. A temporary cvar switched the multiplier in the test build only; this PR has no switch.

The value. The first batch compared x5, x20 and x100 against off (232 matches, 7 maps):

x100 empties the AVOID areas further but adds long stuck episodes elsewhere, because routes shift onto worse ground. x20 keeps most of the gain without that.

Confirmation, x20 against off (160 matches on the 5 maps whose AVOID areas see traffic, 6 repeats):

• stuck events on AVOID areas on sentinel_ctg 8.9 -> 0.2 a match (first batch: 5.0 -> 0.8)
• on skyline 1.1 -> 0.4 (first batch: 1.9 -> 0.3)
• bot time on AVOID areas 183 -> 124 samples a match
• stuck events overall x0.92 [0.76, 1.12] paired, 40 down / 38 up
• kills and fall deaths unchanged

The overall totals of the confirmation batch rise (x1.15) only because of a single match: one sentinel_jgr round in which several bots stuck in the area at the foot of a ladder produced 463 events, 153 of them from one bot. The same spot produces about 105 events over the other matches in either arm.

Risk

Low. Only meshes that mark AVOID are affected, and the cost is finite, so no route is lost.

Toolchain

• Linux GCC Distro Native (Linux Mint 22.3, GCC 13.3.0)

Linked Issues

• related ntre_ridgeline_ctg: navmesh rework and hillside ladder neoAssets#143
• related ntre_tarmac_ctg: navmesh rework neoAssets#149
• related ntre_apparatus_dm: first navmesh neoAssets#157
• related ntre_rise_ctg: navmesh rework neoAssets#160
• related ntre_threadplate_ctg: navmesh rework neoAssets#161
• related ntre_sentinel_ctg: navmesh rework neoAssets#162
• related ntre_sentinel_jgr: navmesh rework neoAssets#165
• related ntre_skyline_ctg: navmesh rework neoAssets#164