New effect for the infolab

Trigonometric sinusoidal strings changing colour across the screen.

web/priv/js_effects/TheStrings.js

@@ -0,0 +1,54 @@
+
+let t = 0;
+
+function make_eq() {
+	const elements = ["Math.sin(i)","Math.cos(i)"];
+	const symbols = [" + ", " - "];
+	let eq = "";
+	for (let i = 0; i < 1+parseInt(Math.random()*3); i++) {
+		let tr = "(i/" + (1+parseInt(Math.random()*3)) + ")";
+		eq += elements[parseInt(Math.random()*elements.length)].replace("(i)",tr);
+		eq += symbols[parseInt(Math.random()*symbols.length)];
+	}
+	return eq.substring(0,eq.length-3);
+}
+
+let eqx = make_eq();
+let eqy = make_eq();
+
+return class TheStrings {
+  constructor(display) {
+    this.display = display;
+
+    this.#clear();
+  }
+
+  #clear() {
+    this.display.flush();
+  }
+
+  dist(a,b) {
+    return (((this.display.width/2)-a)**2 + ((this.display.height/2)-b)**2);
+  }
+
+  update() {
+    t+=0.1;
+    let length = 3;
+    for (let i = t; i < t+length; i+=0.005) {
+      let tx = (this.display.width /2)+(parseInt(eval(eqx)*(this.display.width )/4));
+      let ty = (this.display.height/2)+(parseInt(eval(eqy)*(this.display.height)/4));
+      if (tx > 0 && tx < this.display.width && ty > 0 && ty < this.display.width) {
+        let val = ((i/10)*255)%(255*2);
+		if (val > 255) {
+			val = 255-(val-255);
+		}
+        let val2 = ((i/15)*255)%(255*2);
+		if (val2 > 255) {
+			val2 = 255-(val2-255);
+		}
+        this.display.setPixel(tx, ty, [val,val2,255-val]);
+      }
+    }
+    this.display.flush();
+  }
+}