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import { ctx } from "./main.ts";
import { V2 } from "./util.ts";
const particles = new Set<Particle>()
let particles_to_remove = new Set<Particle>()
export function tick_particles(dt: number) {
particles.forEach(p => p.tick(dt) ? {} : particles_to_remove.add(p))
particles_to_remove.forEach(p => particles.delete(p))
particles_to_remove = new Set()
}
export function draw_particles() {
particles.forEach(p => p.draw())
}
export function particle_count() { return particles.size }
export function particle_splash(pos: V2) {
for (let i = 0; i < 64; i++) {
const p = new Particle()
p.px = pos.x + 0.5
p.py = pos.y + 0.5
const a = Math.random() * Math.PI * 2
const r = Math.sqrt(Math.random()) * 5.
p.vx = Math.sin(a) * r
p.vy = Math.cos(a) * r
p.decay = 4.
p.tr = Math.sqrt(Math.random()) * 1.
p.c = `hsl(${Math.random() * 0.2 + 0.7}turn, 100%, 50%)`
p.r = Math.random() * 0.1 + 0.03
particles.add(p)
}
}
class Particle {
c = "red"
r = 0.05
tr = 0
px = 0
py = 0
vx = 0
vy = 0
decay = 1
tick(dt: number) {
this.tr -= dt
this.px += this.vx * dt;
this.py += this.vy * dt;
this.vx *= Math.exp(-dt * this.decay)
this.vy *= Math.exp(-dt * this.decay)
return this.tr > 0.
}
draw() {
ctx.fillStyle = this.c
ctx.globalAlpha = Math.min(1, this.tr * 5.)
ctx.beginPath()
ctx.arc(this.px, this.py, this.r, 0, Math.PI * 2)
ctx.fill()
}
}
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