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Naval Movement And Water Pathing

Contract

Warcraft III movement comes from UnitData.slk movetp. OpenRealm recognizes the retail/Warsmash values foot, horse, fly, hover, float, and amph; unknown authored values remain movement-disabled. Routing must preserve the movement type instead of treating every non-flyer as a ground unit.

The shared WPM cell already stores nowalk, nofly, and nowater. WC3 routing exposes these policies through M_UnitStaticPathingFlags():

movetp Static route is blocked when
foot, horse, hover nowalk
fly nofly
float nowater
amph nowalk && nowater

The shared router exposes CM_PATHING_UNSWIMMABLE for nowater and the generic CM_PATHING_REQUIRE_ALL query modifier. WC3 represents amph as REQUIRE_ALL | UNWALKABLE | UNSWIMMABLE, so the route is rejected only when both terrain channels are blocked. The shared router does not contain an amphibious gameplay type. This follows Warsmash MovementType.AMPHIBIOUS, whose pathability is !UNWALKABLE || !UNSWIMABLE.

Pathing Textures

WC3 pathing-texture red blocking applies to both land and naval movement. In OpenRealm's decoded color32_t representation the existing red-source blocking channel is COLOR32.b; stamping a blocked pixel sets both nowalk and nowater. The green-source channel remains nofly.

A live walkable bridge is special: a clear authored deck may clear terrain nowalk so ground units can cross, but it must not clear terrain nowater. FLOAT therefore continues to use the river/water route and never gains a naval route across the bridge deck. Blocked bridge pixels still block both land and water.

Dynamic Collision

Warsmash separates moving-unit collision into ground, sea, and air domains. OpenRealm keeps its existing precise BoxEdicts broad phase but applies the same domain semantics in skills/s_move.c:

Movement Collision domain
foot, horse, hover ground
float sea
amph ground + sea
fly air
disabled none

Two ordinary units block one another when their domain masks overlap. Structures remain precise blockers for ground and sea movement in addition to their authored/coarse static footprint; this preserves OpenRealm's existing protection against leaking through coarse 32-unit building pathing cells. Flyers retain their prior separation from structures in this move-time circle test and rely on authored nofly pathing where present.

Command-time dynamic obstacle stamping is requester-aware. The shared router passes the requesting pathing policy back to WC3's M_UnitDynamicPathingFlags(): ground movers see ground/amphibious blockers, sea movers see sea/amphibious blockers, flyers see air blockers, and amphibious movers see either ground or sea blockers. For an amphibious request, any overlapping ground/sea blocker stamps both selected channels so the static REQUIRE_ALL terrain rule cannot incorrectly treat a lone unit as passable. Static terrain semantics stay generic while dynamic collision-domain policy remains game-owned.

Rendering

Rendering height is separate from simulation pathability. Existing M_CheckGround() behavior remains authoritative:

  • float uses the water surface and ignores walkable bridge height;
  • amph uses the water surface only where terrain is swimmable and not walkable;
  • an amphibious unit on a walkable bridge is not presented as swimming.

Do not use render-water detection to authorize movement.

Existing Consumers

Movement/pathing consumers already call M_UnitStaticPathingFlags() rather than hard-coding ground routing. Fixing that policy therefore propagates to normal Move, Patrol, Attack/chase, attack-move waypoints, formation slots, spawn/unstuck placement, Way Gate placement, Blink-style point correction, construction approaches, and cargo transport movement.

Repair's authored naval range bonus is already implemented separately in skills/s_repair.c for movetp=float targets.

Naga Submerge uses the same terrain truth rather than inventing another water classifier. Asb1/Asb2/Asb3/ANsu may enter the submerged form only when CM_TerrainPointIsSwimmable() is true and CM_TerrainPointIsWalkable() is false. That is an ability activation rule, not an amphibious routing rule: ordinary amph units can still traverse walkable land and water exactly as described above.

Cargo passenger placement already asks G_FindUnitUnstuckPosition() using the passenger, so the passenger's movement policy is authoritative. The current last-resort unload fallback still places the passenger at the transport position if no legal unstuck point exists. Retail-exact behavior for the no-legal-unload-position case remains unresolved and is deliberately not changed by the naval routing work.

Verification

Automated coverage belongs in games/warcraft-3/game/tests/t_pathfinding.c and t_movement.c:

  • land rejects float while water accepts it;
  • amph accepts either land or water and rejects cells blocked to both;
  • movement type selects the expected router policy;
  • command-time amphibious destinations reject either a ground or sea unit while ground/sea movers ignore the opposite domain;
  • a float route detours through connected water around unswimmable land;
  • pathing-texture blocked pixels reject both ground and float routing;
  • float move-time collision ignores ground units and collides with sea units;
  • amphibious move-time collision collides with both ground and sea units;
  • existing water-height/bridge tests continue to cover FLOAT presentation.

Per repository policy, build affected targets and run make test before committing code changes.