1 files changed, 121 insertions, 0 deletions
diff --git a/src/relabi/index.js b/src/relabi/index.js
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+++ b/src/relabi/index.js
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+import * as Tone from "tone";
+import kalimba from "../lib/kalimba";
+import { randrange } from "../lib/util";
+
+const TWO_PI = 2 * Math.PI;
+
+/**
+ * Wave functions
+ */
+const WAVE_FUNCTIONS = {
+  sine: Math.cos,
+  triangle: (time) =>
+    (4 / TWO_PI) *
+      Math.abs(
+        ((((time - TWO_PI / 4) % TWO_PI) + TWO_PI) % TWO_PI) - TWO_PI / 2
+      ) -
+    1,
+  square: (time) => (time % TWO_PI < Math.PI ? 1 : -1),
+  saw: (time) => ((time % TWO_PI) - Math.PI) / Math.PI,
+};
+
+class Relabi {
+  /**
+   * Initialize relabi generator
+   */
+  constructor() {
+    this.updateTime = 1.0;
+    this.steps = 100;
+    this.waves = [
+      { type: "sine", frequency: randrange(0.5, 2) },
+      { type: "sine", frequency: randrange(0.5, 2) },
+      { type: "sine", frequency: randrange(1, 10) },
+      { type: "sine", frequency: randrange(5, 10) },
+    ];
+    this.bounds = [-0.5, 0.5];
+    this.frequencies = [220, (220 * 3) / 2, 440, (440 * 3) / 2];
+  }
+
+  /**
+   * Start the generator
+   */
+  start() {
+    console.log("Start Relabi");
+    this.stop();
+    this.clock = new Tone.Clock((time) => this.step(time), this.updateTime);
+    this.clock.start();
+  }
+
+  /**
+   * Stop the generator and reset it
+   */
+  stop() {
+    if (this.clock) {
+      this.clock.stop();
+      this.clock.dispose();
+    }
+  }
+
+  /**
+   * Generate relabi events
+   */
+  step(time) {
+    const waveCount = this.waves.length;
+    const boundsCount = this.bounds.length;
+    let previousValue = this.previousValue;
+    let index;
+    let step;
+    let value;
+    let noteCount = 0;
+
+    // Generate several events per second
+    for (step = 0; step < this.steps; step += 1) {
+      // Time offset for this event
+      const offset = time + (step * this.updateTime) / this.steps;
+
+      // Initialize value
+      value = 0;
+
+      // Compute the wave functions for this event
+      for (index = 0; index < waveCount; index += 1) {
+        const wave = this.waves[index];
+        value += WAVE_FUNCTIONS[wave.type](offset * wave.frequency);
+      }
+
+      // Scale to [-1, 1]
+      value /= waveCount / Math.PI;
+
+      // Compute whether we crossed a boundary, and which direction
+      for (index = 0; index < boundsCount; index += 1) {
+        const bound = this.bounds[index];
+        if (value < bound && bound < previousValue) {
+          // Going down
+          this.trigger(offset, index * 2);
+          noteCount += 1;
+        } else if (value > bound && bound > previousValue) {
+          // Going up
+          this.trigger(offset, index * 2 + 1);
+          noteCount += 1;
+        }
+      }
+
+      // Update the previous value
+      previousValue = value;
+    }
+
+    // Store the latest value
+    this.previousValue = value;
+
+    console.log(`Tick ${Math.floor(time)}, played ${noteCount} notes`);
+  }
+
+  /**
+   * Trigger an event
+   */
+  trigger(time, index) {
+    // console.log("trigger index", index, time);
+    kalimba.play(this.frequencies[index], time);
+  }
+}
+
+export default Relabi;