Particles demo

A dark stone floor at dusk with a stone in the middle, and every effect in the engine's particle library playing on it: fire, a campfire, a torch, explosions, smoke, steam, dust, dirt, sparks, welding, a muzzle flash, wood and stone chips, glass, a splash, rain, snow, leaves, confetti, fireworks, magic, healing, a shockwave and coins. Pick one and it plays on the stone (bursts again every few seconds, streams keep going), or turn on "All at once" to see the whole library round a circle.

The demo teaches two engine pieces: kke::ParticleEffects, which simulates and draws a few thousand particles of five kinds (smoke, sparks, glows, flakes and rings), and kke::ParticleLibrary, which plays effects by name from YAML or JSON. Start here for fire, smoke, impacts, weather, magic or celebrations in a game.

Run it

The executable is particles_demo (kke_add_game(particles_demo ...) in CMakeLists.txt). It needs no optional library and no asset pack.

cmake --build build --target particles_demo
cd build/bin
./particles_demo
KKE_PARTICLES_EFFECT=explosion ./particles_demo   # start with one effect
KKE_PARTICLES_ALL=1 ./particles_demo              # start with all at once

Variable	Effect
KKE_PARTICLES_EFFECT=<name>	the effect to start with (a name from the table in docs/PARTICLE_EFFECTS.md)
KKE_PARTICLES_ALL=1	start with every effect at once
KKE_SKIP_INTRO=1	skip the logo intro (engine-wide)

Controls

Action	Keyboard / mouse	Controller
Previous / next effect (particles.previous, particles.next)	Left / Right	LB / RB
Play it again (particles.play)	Space	A (south)
All at once on / off (particles.all)	A	Y (north)
Turn the camera	left-drag	right stick
Zoom	wheel	d-pad
Settings panel	F3, or click	View

Rebindings are saved to particles_demo_input.json. The panel also has "Bursts again by themselves" (and how often), a size slider (x0.25 to x3) and wind (-8 to 8 m/s, which carries smoke, fire and flakes).

How it works

ParticlesDemoModule.cpp:

• init() makes a kke::ParticleEffects (12000 particles at most) and a kke::ParticleLibrary on it, which starts with the built-in effects, then loads every .yaml, .yml or .json in assets/effects/ beside the game: your own effects, or new versions of built-in ones.
• restart() stops everything and plays the chosen effect on the stone (play() for a burst, start() for one with a steady stream, as ParticleLibrary::looping() says), or one per stone round the circle. Weather (rain, snow) falls from 7 m over the whole floor instead; only the leaves fall in "all at once", the rest would bury the gallery.
• update() plays bursts again every few seconds and calls m_library->update(dt, wind), which emits for everything running and moves every particle.
• renderTranslucent() draws them: flakes and smoke sorted back to front, then glows, rings and sparks added as light.

Make a game like this

Copy an effect from ParticleLibrary::builtInYaml() (or the table in docs/PARTICLE_EFFECTS.md) into assets/effects/my_effects.yaml, rename it, change its numbers, and play it where something happens:

m_library->play("wood_chips", { crate.position });                // a crate breaks
m_library->play("sparks", { hit.point, hit.normal, car.velocity }); // metal scrapes
auto fire = m_library->start("campfire", { camp });                 // keeps burning

Files

File	What
main.cpp	the modules: input, UI, audio, orbit camera, the demo, its panel
ParticlesDemoModule.h / .cpp	the gallery
game.json	the marketplace entry
engine/include/kke/ParticleEffects.h, ParticleLibrary.h	the engine pieces
shaders/effect*.vert/frag	how each kind is drawn