Entropie – architecture

How the code is put together. Read before adding a feature; update it in the same version when the structure changes (rules for working on it: RULES.md).

Modules

• render knows nothing of the world: it gets meshes, matrices and plain numbers.
• world and people are one layer: an Object owns its Body, Ai and Hands.
• *_internal.h: shared inside one module only.

One frame

Game_update → input, actions, talk, player → World_update: physics for every object (near ones from the Grid) → grid rebuilt → felling and cutting → hands (pushing, carrying) → hose → AI → bodies animated → props (gates, chairs, ashtray, pullovers put down). Then the camera follows (game.c), and Game_render: shadow pass, scene pass (terrain, objects, figures, grass), the sky, Game_renderAir (rain, smoke, chips: after the sky, so they show against it), ink pass, UI. Sound_update (main.c) after the update: the world's noises of the frame and the steady sounds.

Budget: the update takes about 1 ms for ~950 objects. Drawing skips what's out of view (objects, 8×8 terrain tiles).

Objects

• One struct for every thing (world/object.h): type, variant, size,

position, rotation (yaw rotation.y), up to 3 oriented box colliders.

• Fields only some kinds use are commented with the kind ("characters:",

"gates:", "chairs:"). Objects start zeroed: zero must be a safe default.

• is_static: never moved by physics. Only their own code moves them

(Object_swingGate, Object_slideChair), then Object_syncColliders.

• Meshes come from Shapes_* and are rebuilt only when what they show changes

(shown pattern in world.c showProps).

Space and turning

• y up, meters, seconds. Yaw: local +X turns to (cos, 0, sin), +Z to (-sin, 0, cos).
• yaw_along(dir): lengths along +X (logs, gates, wall pieces).

yaw_facing(dir): fronts along +Z (furniture, doors, windows, chairs). yaw_front(yaw): where a front points.

• The courtyard: court(a, b) in site.c. The main building: local x along

it, +z towards the yard (manor.c).

Building the map

Scene_load (start things) → Site_build (static things, buildings, roads) → World_buildTerrain (levels the ground under static things) → Site_finish / Scene_finish (things that sit on the ground).

• Buildings you walk into (manor.c): a Plan of boxes (box, wallX,

wallZ with gaps, opening). The look is one OBJ_STRUCTURE mesh, the solid parts invisible OBJ_WALLs.

• Below the ground: Terrain_addPit (a turned rectangle). The ground's height

there is the pit floor, the ground isn't drawn there (holes in scene.frag).

Physics

• Per object, against near objects and the terrain. Characters: walk up stairs

(up to SNAP_UP_MOST), higher edges and things to step over or onto are a set move (over_t, beginStepOver); sitting down is a set move too (sit_moving).

• Rays: Collider_ray / Object_rayToCollider (one box), World_rayCast

(the first thing along a ray, with a skip filter). Down to the ground: World_groundHeight.

Rendering

• One scene shader for everything not a figure: uniforms switch it to terrain

(terrainSize), decals, grass, glow. Figures have their own shader. The ink pass draws the outlines over it all.

• New GL calls: add them to the list in core/gl.h.

Sound

• core/audio.c: SDL3 audio stream, mixed on the audio thread. Short voices

(noise, sine, saw or crackle; filters; attack and decay; pan; delay) and steady beds (wind, rain, fire, chainsaw, engine, crickets, hose) turned up and down. No device: silent, nothing else changes.

• The world queues what makes a sound this frame: World_noise (steps with

what's underfoot, chops, clinks, glass, thuds, a tree coming down, twigs). game/sound.c empties the list each frame and plays them by distance and side from the camera; the beds follow the weather, the fires, a chainsaw, the car.

• M mutes; menus pause the beds.

Crates

• Each slot is known (Object.crate_slot: kind and sips, CRATE_SLOT):

stored, crate_empties and the weight follow from it (Crate_recount). Bottles of another kind put into a crate stay there as such until somebody sorts them (Crate_takeWrong, the tidy: ai_help.c sortCrates).

Saves

• src/game/save.c: <name>.sav (text: key value lines, [game], then [o id] per object) and <name>.ground (binary: the wear map, the wet chunks). In the user's data folder (Platform_saveDir).
• Loading builds the world as at the start (Game_initWorld(game, false): no drive in), finds the scene's things by scene_id / spawn / spawn_type (set when the scene is built), makes the rest anew (Object_create with the saved type, palette, size and make_arg), then sets the fields and rebuilds what looks different (trees, tents, gear, crates, bags, bottles, ladders, pullovers, the car).
• What's saved: the tables THING and PERSON in save.c (plus skills, likes, keys, hands, the car's boot, asleep). Buildings, walls, roads, bushes: only found again.
• Keeping old saves working:
• A new field: add it to a table. Old saves don't have it: it keeps what the fresh world gives it.
• A key renamed or its meaning changed: raise SAVE_FORMAT (save.h) and add a step to migrate() that rewrites the old lines.
• A save from a newer format is refused, never guessed at.
• A thing the scene no longer makes is dropped; one it newly makes keeps its fresh state.
• Not kept (comes back fresh): what anybody was in the middle of (AI plans, paths, poses), sparks and smoke. Kept specially: the hose's rope (rope line: every point, melted, taped), who sits where (sit line: sat down again, staying a while), who's up a ladder (ladder line: you back on it as high, Ladder_mountAt; the others at its foot), what's in each crate slot (slots line; older saves: their own bottles, so many full and empty), holding on to something together (grab, help lines).

Versions

Makefile VERSION; the build id is an md5 of sources and assets (make version). STATE.md ends with the version it describes.