Siege engine presentation

Roman and Carthaginian ballistas and catapults use reinforced timber carriages, open spoked wheels with iron tyres, bronze straps and hubs, and short moving standards. The presentation scale is 1.35x for ballistas and 1.20x for catapults, applied after the troop profile's scale; simulation footprints and combat values are unchanged.

render/entity/siege_renderer_common.cpp owns the shared wheel construction, regalia, carriage motion and travel history. Each registered renderer keeps its own bounded history by entity id, shared when the renderer function is copied. Wheel angles integrate signed rendered displacement and turning, using the actual model scale and wheel radius. Stopped wheels retain their orientation, while carriage sway eases down. World changes, replay rewinds, long gaps and teleports reset the history. Previews use temporary state. No simulation components are written by these animations.

Loading reads CatapultLoadingComponent: the winding stroke eases at both ends and turns the crank and rope drum. Ballista arms flex together with their nocks and string. Firing releases the mechanism quickly, kicks the carriage backwards, and lets the catapult arm rebound against its padded stop. Loaded ammunition vanishes when the simulation enters Firing, when the live projectile is spawned; the ready pose still displays it. Incendiary stones retain their existing flame effect.

Crews

Every catapult carries four builders and every ballista three, drawn as presentation-only humanoids through the civilian actor path (render/entity/siege_crew.{h,cpp}). They use each nation's builder look -- register_nation_crew_rig in each builder_renderer.cpp registers the builder visual spec, idle loadout and builder palette, and civilian_render_scale resolves the builder troop scale for that rig -- so Roman engines are worked by Roman engineers and Carthaginian by Punic ones. No simulation state exists for them: the unit is still one man in the game.

The crew has three jobs, chosen from the carriage motion and CatapultLoadingComponent:

Stations are written in the engine's local frame: an anchor in carriage units scaled by the presentation scale, plus a body offset in metres so hands meet the timber. A crewman walks between stations at 0.95 m/s, turns with an exponential ease rather than snapping, and fades the outgoing clip over 0.32 s. The push stride is phased from the distance the engine has actually rolled (SiegeTravelState::travelled, 0.60 m per stride), so feet do not slide and a stopped engine stops its crew mid-step. The crank phase follows loading_time, and the heave follows loading_progress, so the loader presses the stone or bolt in just before the renderer shows it seated.

crew_push, crew_crank and crew_heave are clips 82-84, baked by bpat_baker from HumanoidConstructionPoseKind::CrewPush/CrewCrank/CrewHeave in animation/attack_pose_manifest.cpp; the push bakes a real walk (bake speed 1.1) and layers the braced arms over it. Review them with humanoid_preview --clip crew_push --view side --report; bone stretch stays at or below the idle clip's.

Crews are skipped beyond 110 m or below 16 px, and draw at Minimal detail below 34 px. SiegeCrewTest.* covers the jobs, push stations, stride locking, load phasing and blending.

Review both nations with real movement and repeated projectile launches:

build-home/bin/arena_app --scenario siege_roman_showcase
build-home/bin/arena_app --scenario siege_carthage_showcase

The SiegeMotion.* tests cover travel, parking, pivot turns, scaled wheel circumference, replay/teleport resets, release timing and recoil settling. The showcase scenarios also check projectile impact synchronization.

Walls, ladders and siege towers

The palisade's wall walk is a timber balcony on the town face; its measurements live in game/core/wall_walk_geometry.h so troops' feet meet the planks. A company reaches it by a stair (every fourth straight segment) or by a ladder a builder raises. A ladder is a wall piece built like a gate: the builder card places it against the town face of one of your own straight wall segments and nowhere else (not outside, not on a stretch with a stair or a ladder already). Climbers go up a ladder hand over hand in the climb_ladder clip, whose phase follows each man's height, two rungs a cycle, so hands and feet stay on the rungs; they come down facing the rungs and queue a body length apart. After the leader steps off, the troop stays in the Leaving phase until the rest of the file is down.

A siege tower carries no troops of its own. Sent at an enemy wall (a move next to it, or an attack order on the wall or gate) it rolls up between two posts, squares up and lowers its bridge. Infantry escorting it within 14 m is then called up; any idle infantry that later walks up behind a docked tower climbs it too, and a docked tower stays a bridge for as long as it stands. Each man walks round to the back, climbs the inner ladder, crosses the bridge onto the enemy balcony and from there can go down the enemy's stairs into the town. Wet hides turn most arrows (ranged damage ×0.3) and rams and towers only ever engage structures.

Defenders on a wall walk shoot from height (×1.35 for archers and spearmen instead of a hill's ×1.8) and the stakes cover them from arrows shot up from the ground (×0.65). A computer-held town with a garrison posture posts its archers onto the stretch of balcony nearest an assault (RampartBehavior, see AI_ARCHITECTURE.md), and once there its commander leaves them as the wall's garrison.