particle fun

1 files changed, 60 insertions, 0 deletions

diff --git a/test-client/particles.ts b/test-client/particles.ts
new file mode 100644
index 00000000..ba695cc0
--- /dev/null
+++ b/test-client/particles.ts
@@ -0,0 +1,60 @@
+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()
+    }
+}
+