Sea demo

Pirate ships on an open sea. Pick a ship from Synty's POLYGON Pirate Pack, from a rowing boat up to a three-masted man-o'-war, each with its own speed, turning and guns. Set the sails, steer with the wind, hold the aim button to see where a broadside will fall, and fire. Cannonballs fly in a real arc, splash, punch dents and splinters into hulls, snap masts and sink ships; wrecks, masts and splinters float on the same waves you see. An island fort's wooden palisade splinters for real with FEMFX in builds that have it. Up to four people share one screen (split screen), and a friend can sail along online.

It is a showcase, not a whole game: three modes (battle, target practice, free sail), a settings panel for wind, waves, guns and enemies, and everything a naval game needs underneath. Start here for a pirate game, a naval shooter, a sailing game or anything that floats.

Run it

cmake --build build --target sea_demo
cd build/bin
./sea_demo
KKE_SKIP_INTRO=1 ./sea_demo         # skip the logo intro
KKE_MOOD=stormy ./sea_demo          # the same sea under another mood

The ships need the POLYGON Pirate Pack (see Assets); without it they are built from boxes and everything else works the same.

Developer switches (ignored in shipping builds):

Variable	Effect
KKE_SEA_START=1	Sail at once with the start menu's saved choices (headless checks)
KKE_SEA_MODE=0/1/2	Battle, target practice or free sail
KKE_SEA_ENEMIES=n	n enemy ships (0-6)
KKE_SEA_SHIP=0-4	Player 1's ship: rowing boat, longboat, schooner, brig, man-o'-war
KKE_NET=host, KKE_NET=join:ADDRESS	Host or join online at startup
KKE_LOBBY_JOIN=n	n more controllers join the start menu (LOBBY.md)

# A battle with three enemies, headless, with a screenshot:
KKE_SEA_START=1 KKE_SEA_ENEMIES=3 tools/check_game sea_demo --seconds 30 --shot sea.jpg

Controls

All actions are rebindable (Settings, Controls); SeaDemoModule::defineInput in SeaDemoModule.cpp makes them.

Action	Keyboard / mouse	Controller
Steer	A / D or Left / Right	left stick, sideways
Sails: up a step / down a step (oars: row)	W / S or Up / Down	left stick, up / down
Aim the guns (shows the arc and where it lands)	hold right mouse button	hold LT
Fire a broadside	left click or Space	RT
Turn the camera	Q / E, or drag with the right or middle button	right stick
Camera closer / further	mouse wheel	d-pad up / down
Next ship	Tab	Y (north)
Throw something overboard	T	d-pad right
Next thing to throw	G (or keys 1-5)	d-pad left
Pause menu (Change ship, Restart, Settings)	Esc	Start

The guns fire to the side the camera looks at: look left of the bow and the port guns fire, right and the starboard guns fire. Look up to aim further. With Aim help on, the guns also pick up the range to the nearest enemy on that side and lead it.

How it plays

The start menu (kke::LobbyModule) picks each player's ship, the mode, the enemy ship type, how many enemies (the CPU row) and how good they are, and Online (Off, Join, Host). Another controller joins with A for split screen.

Ship	Speed	Turning	Guns	Feel
Rowing boat	3.6 m/s, rowed	45°/s	1 swivel gun a side	darts around, sinks in a few hits
Longboat	4.6 m/s, rowed	32°/s	2 a side	steady, no wind needed
Schooner	9.5 m/s	20°/s	4 a side	quickest under sail, light guns
Brig	8.5 m/s	13°/s	8 a side	the all-rounder (default)
Man-o'-war	7 m/s	8.5°/s	7 a side on two decks, 24-pounders	slow to start and turn, hits hardest

Sailing ships carry way: they speed up and slow down slowly, turn faster at speed, and go fastest with the wind from behind (turn Wind fills the sails off for the same speed in every direction). Rowing boats ignore the wind.

• Battle: enemy ships approach, turn broadside-on and fire back. Sunk enemies come back unless that row is off; a sunk player gets a new ship after a few seconds.
• Target practice: enemies lie at anchor closer in, waiting to be sunk.
• Free sail: no enemies; throw things overboard and watch the sea.

How it works

Ships (Ships.h, Ships.cpp)

ShipClass is one row per ship: the Synty file names of its hull, masts, sails and rigging, its size, handling, guns and health. ShipArtLibrary loads each class's parts once. The parts of one ship share an origin, so they load raw (fixUnitMismatch = false) and the whole set is scaled by 100 when the hull is in centimetres (raw length under 2). Each sail is matched to the nearest mast by position, so a snapped mast takes its sails with it. The hull's vertices are kept for dents.

Sailing (SeaDemoModule::sailShip)

A ship is one kke::FloatingBody box (470 kg/m³, low centre of mass), so buoyancy, pitching and rolling come from the waves. On top: thrust from the sails (scaled by the wind's angle) or the oars against quadratic drag, a keel force that stops it sliding sideways, and a rudder that sets a yaw rate, stronger at speed. Water taken on through damage adds mass, so a holed ship sits lower and slower before it sinks. Ships push each other apart with capsule contacts along the hull (FloatingBodies), so two long hulls can sail side by side.

Guns (Battle.cpp)

A broadside is a rolling volley: each gun fires a few hundredths of a second after the last, from its own muzzle along the side, with a little spread and recoil. Balls are point masses under gravity with no drag, so the predicted arc (predictArc) is exactly the path they fly, and the ring shows where the first ball lands. Muzzle speed (80 m/s default) and elevation set the range; the camera's pitch sets the elevation, or Aim help solves it for the nearest enemy.

Damage

Hits are cheap on purpose (the ships never use FEMFX): a ball that crosses the hull dents the Synty mesh around the impact point (vertices pushed in, uploaded with ModelModule::setDeformedVertices), throws splinters (small floating planks), sparks and smoke, takes health and can start a fire. A ball through a mast snaps it: the mast and its sails fall into the sea as a floating body. At zero health the ship lists, settles and sinks; its masts and splinters keep floating for a while.

Effects (Effects.cpp)

kke::ParticleEffects (smoke and sparks, 9000 at most): wake foam along the sides and spray at the bow (more with speed), muzzle flashes and white powder smoke, water columns and foam rings where balls land, dust on islands, fire and black smoke on burning ships. Flags stream downwind and sails swell with the wind.

The sea and the world (World.cpp)

kke::OceanWaves (Gerstner swell) is drawn by kke::OceanRenderer out to the horizon: a graded grid (fine near the camera, coarse far away) whose waves fade out where the cells get too big to show them, so the far sea never flickers. Islands are Synty background islands and rocks (low mounds without the pack); ships scrape and stop on them. The fort island has a tower, palms and, with FEMFX, a palisade of five wooden panels.

The FEMFX fort

Each palisade panel is a PhysicsModule::spawnPatternedBox with the Splinters fracture pattern: wood that breaks along the planks. A cannonball that reaches the wall is handed to FEMFX as an iron sphere at 30 m/s (made heavier to keep its momentum, because at 80 m/s it would jump through a plank between steps). The panels spawn unbreakable and arm once they have settled, so they never fall apart under their own weight. Rebuild the fort in the panel puts it back. Builds without FEMFX (KKE_ENABLE_FEMFX=OFF, the default) have no palisade; the panel says so.

What it costs (the panel's fort row shows it live): standing, the panel pieces sleep and FEMFX takes about 0.1 ms a step. While a wall breaks, each moving splinter costs about 0.15-0.2 ms (SCALING.md), so the debris budget keeps 60 splinters at most; six balls into the wall peaked at 8-12 ms a step on a 4-core cloud machine and settled back to 0.1 ms within ten seconds.

Online (SeaNet.cpp)

Every ship is a network player: each screen sends its captains' ships, and the host also sends its enemy ships as extra local players. A ship's state carries its position, orientation, class, team, health, sails and which masts stand. Shots go to everyone as events (drawn, not simulated, on the other screens). A hit is applied by the ship's owner: whoever sees their ball hit a ship they don't own sends a hit event, so a friend's damage, sinking and score stay consistent. A client's own enemies make way for the host's. The friend gets the same options as the host.

Notes from Black Flag

Assassin's Creed IV: Black Flag is the reference for the feel:

• Sails in steps (furled, half, full) instead of a throttle, and a ship that carries way.
• The camera chooses the guns: look to a side and hold aim, and that side's broadside shows where it will land; look up for range.
• A rolling broadside reads better than every gun at once.
• Readable impacts: water columns, splinters, smoke and fire tell you how a fight is going without a health bar.

Here the arc is the real ballistic path (no drag), so a long shot is aimed high and a close one flat, the way a gun crew would.

Tuning

What	Where
Ship speed, turning, guns, health	kClasses in Ships.cpp
Wind, waves, ball speed, damage, aim help	the settings panel (F3, or the pause menu)
How enemies fight	thinkEnemy in Battle.cpp
Fort wood strength, size, debris budget	buildFort in World.cpp
Particle budget	ParticleEffects(..., 9000) in SeaDemoModule::init

Engine features it uses

Feature	Header / module	Doc
Gerstner ocean, CPU and GPU	kke::OceanWaves, kke::OceanRenderer	this page
Buoyant bodies with capsule contacts	kke::FloatingBodies (tests/test_floating_bodies.cpp)	cookbook: physics
Synty models, dents	kke::ModelModule, kke::AssetCatalog	ASSETS.md
Breakable wood	kke::PhysicsModule (FEMFX)	SCALING.md
Particles	kke::ParticleEffects
Start menu, split screen	kke::LobbyModule, kke::splitScreen	LOBBY.md
Title, pause, settings	kke::GameShellModule	GAME_SHELL.md
Online	kke::NetModule	NETWORKING.md
Settings panel	kke::DemoPanelModule	DEMO_PANEL.md
Third-person camera	kke::CameraRig

Nothing of the ocean or ships is exposed to Lua yet, so a game of this kind is C++ for now.

Assets

Synty POLYGON Pirate Pack (POLYGON_Pirate_Pack), found at runtime in assets/synty/ or KKE_ASSETS_DIR; never committed. Used: the hulls, masts, sails and rigging of SM_Veh_Boat_Rowing_01, SM_Veh_Boat_Small_01, SM_Veh_Boat_Medium_01, SM_Veh_Veh_Boat_Large_01 / SM_Veh_Boat_Large_* and SM_Veh_Boat_Warship_01; SM_Flag_Pirate_01, the British and Spanish flags; SM_Env_Background_Island_01/02/03, SM_Env_Rock_Huge_01/03, SM_Env_PalmTree_01/02/03 and SM_Bld_Fort_Tower_01. Things thrown overboard are boxes built in code. The log lists every file it loaded ("pack assets used").

Make a game like this

1. Copy the folder (cp -r games/sea_demo games/my_ships), rename the target in CMakeLists.txt, the namespace kke_sea and add the folder to the root CMakeLists.txt.
2. Add or change ships as rows in kClasses: Synty names, size, handling and guns.
3. Make the rules: a convoy to protect, a treasure to carry home, a fort to take. m_ships, damageShip and startSinking are the hooks.
4. Pitfalls: physics goes in fixedUpdate, drawing interpolates with ctx.alpha; FEMFX objects must never overlap when spawned (they push apart hard enough to break); set NetModule::playerCharacter before hosting or joining, because it is sent once.

Files

File	What is in it
main.cpp	The application and its modules
SeaDemoModule.h	The module and all its state
SeaDemoModule.cpp	Start, sailing, controls, camera, split screen, drawing, the panel
Ships.h / Ships.cpp	Ship classes and their Synty art
Battle.cpp	Aiming, broadsides, cannonballs, damage, masts, sinking, enemy captains
Effects.cpp	Splashes, wakes, smoke, fire, splinters
World.cpp	Islands, the fort, the FEMFX palisade
SeaNet.cpp	Online
game.json	Marketplace manifest