feat(examples): update ramp-synth oscillator (6x unison)

thi-ng · Dec 15, 2019 · e4e8b98 · e4e8b98
1 parent d25584e
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Showing 3 changed files with 20 additions and 10 deletions.
diff --git a/examples/ramp-synth/README.md b/examples/ramp-synth/README.md
@@ -13,8 +13,8 @@ visualization to move their position. Markers cannot be moved past their
 neighbors.
 
 Audio must be explicitly enabled by pressing `a`. Sonification uses the
-current ramp as wave table for a 2-voice oscillator w/ 30 Hz base
-frequency.
+current ramp as wave table for a 6-voice unison stereo oscillator w/ 60
+Hz base frequency (configurable via `BASE_FREQ` in `api.ts`).
 
 ### Hotkeys
 

diff --git a/examples/ramp-synth/src/api.ts b/examples/ramp-synth/src/api.ts
@@ -7,7 +7,7 @@ export const PAD = 20;
 export const CWIDTH = WIDTH - 2 * PAD;
 export const CHEIGHT = HEIGHT - 2 * PAD;
 export const SNAP = 5 / WIDTH;
-export const BASE_FREQ = 30;
+export const BASE_FREQ = 60;
 
 export const PRESETS: Vec[][] = [
     [

diff --git a/examples/ramp-synth/src/audio.ts b/examples/ramp-synth/src/audio.ts
@@ -1,3 +1,4 @@
+import { fract } from "@thi.ng/math";
 import { IRamp } from "@thi.ng/ramp";
 
 let actx: AudioContext | undefined;
@@ -9,7 +10,7 @@ export const isAudioActive = () => !!actx;
 export const initAudio = (freq: number) => {
     if (actx) return;
     actx = new AudioContext();
-    buf = actx.createBuffer(1, actx.sampleRate / freq, actx.sampleRate);
+    buf = actx.createBuffer(2, actx.sampleRate / freq, actx.sampleRate);
     src = actx.createBufferSource();
     src.buffer = buf;
     src.loop = true;
@@ -23,13 +24,22 @@ export const stopAudio = () => {
     actx = undefined;
 };
 
-export const updateAudio = (ramp: IRamp, osc2freq = 2) => {
+export const updateAudio = (ramp: IRamp, detune = 0.01) => {
     if (!actx) return;
-    const bufData = buf.getChannelData(0);
-    for (let i = 0, n = bufData.length; i < n; i++) {
-        const t = i / n;
+    const left = buf.getChannelData(0);
+    const right = buf.getChannelData(1);
+    const f4 = 1 + detune;
+    const f5 = 2 + detune;
+    const f6 = 4 + detune;
+    for (let i = 0, n = left.length; i < n; i++) {
+        let t = i / n;
         const y1 = ramp.at(t);
-        const y2 = ramp.at(t * osc2freq);
-        bufData[i] = y1 + y2 - 1;
+        const y2 = ramp.at(t * 2);
+        const y3 = ramp.at(t * 4);
+        const y4 = ramp.at(fract(t * f4));
+        const y5 = ramp.at(fract(t * f5));
+        const y6 = ramp.at(fract(t * f6));
+        left[i] = y1 * 0.5 + y5 * 0.2 + y3 * 0.3 - 1;
+        right[i] = y4 * 0.5 + y2 * 0.3 + y6 * 0.2 - 1;
     }
 };