برچسب: API

Sound is vibration, vision is vibration you can see. I’m always chasing the moment those waves overlap. For a recent Webflow & GSAP community challenge focusing on GSAP Draggable and Inertia Plugin, I decided to push the idea further by building a futuristic audio-reactive visualizer. The concept was to create a sci-fi “anomaly detector” interface that reacts to music in real time, blending moody visuals with sound.

The concept began with a simple image in my mind: a glowing orange-to-white sphere sitting alone in a dark void, the core that would later pulse with the music. To solidify the idea, I ran this prompt through Midjourney: “Glowing orange and white gradient sphere, soft blurry layers, smooth distortion, dark black background, subtle film-grain, retro-analog vibe, cinematic lighting.” After a few iterations I picked the frame that felt right, gave it a quick color pass in Photoshop, and used that clean, luminous orb as the visual foundation for the entire audio-reactive build.

The project was originally built as an entry for the Webflow × GSAP Community Challenge (Week 2: “Draggable & Inertia”), which encouraged the use of GSAP’s dragging and inertia capabilities. This context influenced the features: I made the on-screen control panels draggable with momentum, and even gave the 3D orb a subtle inertia-driven movement when “flung”. In this article, I’ll walk you through the entire process – from setting up the Three.js scene and analyzing audio with the Web Audio API, to creating custom shaders and adding GSAP animations and interactivity. By the end, you’ll see how code, visuals, and sound come together to create an immersive audio visualizer.

Setting Up the Three.js Scene

To build the 3D portion, I used Three.js to create a scene containing a dynamic sphere (the “anomaly”) and other visual elements. 

We start with the usual Three.js setup: a scene, a camera, and a renderer. I went with a perspective camera to get a nice 3D view of our orb and placed it a bit back so the object is fully in frame. 

An OrbitControls is used to allow basic click-and-drag orbiting around the object (with some damping for smoothness). Here’s a simplified snippet of the initial setup:

// Initialize Three.js scene, camera, renderer
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(75, window.innerWidth/window.innerHeight, 0.1, 100);
camera.position.set(0, 0, 10);  // camera back a bit from origin

const renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

// Add OrbitControls for camera rotation
const controls = new THREE.OrbitControls(camera, renderer.domElement);
controls.enableDamping = true;
controls.dampingFactor = 0.1;
controls.rotateSpeed = 0.5;
controls.enableZoom = false; // lock zoom for a more fixed view

Next, I created the anomaly object. This is the main feature: a spiky wireframe sphere that reacts to audio. Three.js provides shapes like SphereGeometry or IcosahedronGeometry that we can use for a sphere. I chose an icosahedron geometry because it gives an interesting multi sided look and allows easy control of detail (via a subdivision level). The anomaly is actually composed of two overlapping parts:

• Outer wireframe sphere: An IcosahedronGeometry with a custom ShaderMaterial that draws it as a glowing wireframe. This part will distort based on music (imagine it “vibrating” and morphing with the beat).
• Inner glow sphere: A slightly larger SphereGeometry drawn with a semi-transparent, emissive shader (using the backside of the geometry) to create a halo or aura around the wireframe. This gives the orb a warm glow effect, like an energy field.

I also added in some extra visuals: a field of tiny particles floating in the background (for a depth effect, like dust or sparks) and a subtle grid overlay in the UI (more on the UI later). The scene’s background is set to a dark color, and I layered a background image (the edited Midjourney visual) behind the canvas to create the mysterious-alien landscape horizon. This combination of 3D objects and 2D backdrop creates the illusion of a holographic display over a planetary surface.

Integrating the Web Audio API for Music Analysis

With the 3D scene in place, the next step was making it respond to music. This is where the Web Audio API comes in. I allowed the user to either upload an audio file or pick one of the four provided tracks. When the audio plays, we tap into the audio stream and analyze its frequencies in real-time using an AnalyserNode. The AnalyserNode gives us access to frequency data. This is a snapshot of the audio spectrum (bass, mids, treble levels, etc.) at any given moment, which we can use to drive animations.

To set this up, I created an AudioContext and an AnalyserNode, and connected an audio source to it. If you’re using an <audio> element for playback, you can create a MediaElementSource from it and pipe that into the analyser. For example:

// Create AudioContext and Analyser
const audioContext = new (window.AudioContext || window.webkitAudioContext)();
const analyser = audioContext.createAnalyser();
analyser.fftSize = 2048;                  // Use an FFT size of 2048 for analysis
analyser.smoothingTimeConstant = 0.8;     // Smooth out the frequencies a bit

// Connect an audio element source to the analyser
const audioElement = document.getElementById('audio-player');  // <audio> element
const source = audioContext.createMediaElementSource(audioElement);
source.connect(analyser);
analyser.connect(audioContext.destination);  // connect to output so sound plays

Here we set fftSize to 2048, which means the analyser will break the audio into 1024 frequency bins (frequencyBinCount is half of fftSize). We also set a smoothingTimeConstant to make the data less jumpy frame-to-frame. Now, as the audio plays, we can repeatedly query the analyser for data. The method analyser.getByteFrequencyData(array) fills an array with the current frequency magnitudes (0–255) across the spectrum. Similarly, getByteTimeDomainData gives waveform amplitude data. In our animation loop, I call analyser.getByteFrequencyData() on each frame to get fresh data:

const frequencyData = new Uint8Array(analyser.frequencyBinCount);

function animate() {
  requestAnimationFrame(animate);

  // ... update Three.js controls, etc.
  if (analyser) {
    analyser.getByteFrequencyData(frequencyData);
    // Compute an average volume level from frequency data
    let sum = 0;
    for (let i = 0; i < frequencyData.length; i++) {
      sum += frequencyData[i];
    }
    const average = sum / frequencyData.length;
    let audioLevel = average / 255;  // normalize to 0.0–1.0
    // Apply a sensitivity scaling (from a UI slider) 
    audioLevel *= (sensitivity / 5.0);
    // Now audioLevel represents the intensity of the music (0 = silence, ~1 = very loud)
  }

  // ... (use audioLevel to update visuals)
  renderer.render(scene, camera);
}

In my case, I also identified a “peak frequency” (the frequency bin with the highest amplitude at a given moment) and some other metrics just for fun, which I display on the UI (e.g. showing the dominant frequency in Hz, amplitude, etc., as “Anomaly Metrics”). But the key takeaway is the audioLevel – a value representing overall music intensity – which we’ll use to drive the 3D visual changes.

Syncing Audio with Visuals: Once we have audioLevel, we can inject it into our Three.js world. I passed this value into the shaders as a uniform every frame, and also used it to tweak some high-level motion (like rotation speed). Additionally, GSAP animations were triggered by play/pause events (for example, a slight camera zoom when music starts, which we’ll cover next). The result is that the visuals move in time with the music: louder or more intense moments in the audio make the anomaly glow brighter and distort more, while quiet moments cause it to settle down.

Creating the Audio-Reactive Shaders

To achieve the dynamic look for the anomaly, I used custom GLSL shaders in the material. Three.js lets us write our own shaders via THREE.ShaderMaterial, which is perfect for this because it gives fine-grained control over vertex positions and fragment colors. This might sound difficult if you’re new to shaders, but conceptually we did two major things in the shader:

1. Vertex Distortion with Noise: We displace the vertices of the sphere mesh over time to make it wobble and spike. I included a 3D noise function (Simplex noise) in the vertex shader – it produces a smooth pseudo-random value for any 3D coordinate. For each vertex, I calculate a noise value based on its position (plus a time factor to animate it). Then I move the vertex along its normal by an amount proportional to that noise. We also multiply this by our audioLevel and a user-controlled distortion factor. Essentially, when the music is intense (high audioLevel), the sphere gets spikier and more chaotic; when the music is soft or paused, the sphere is almost smooth.
2. Fresnel Glow in Fragment Shader: To make the wireframe edges glow and fade realistically, I used a fresnel effect in the fragment shader. This effect makes surfaces more luminous at glancing angles. We calculate it by taking the dot product of the view direction and the vertex normal – it results in a value that’s small on edges (grazing angles) and larger on faces directly facing the camera. By inverting and exponentiating this, we get a nice glow on the outline of the sphere that intensifies at the edges. I modulated the fresnel intensity with the audioLevel as well, so the glow pulsates with the beat.

Let’s look at a simplified version of the shader code for the outer wireframe sphere material:

const outerMaterial = new THREE.ShaderMaterial({
  uniforms: {
    time:      { value: 0 },
    audioLevel:{ value: 0 },            // this will be updated each frame
    distortion:{ value: 1.0 },
    color:     { value: new THREE.Color(0xff4e42) }  // a reddish-orange base color
  },
  wireframe: true,
  transparent: true,
  vertexShader: `
    uniform float time;
    uniform float audioLevel;
    uniform float distortion;
    // (noise function omitted for brevity)

    void main() {
      // Start with the original position
      vec3 pos = position;
      // Calculate procedural noise value for this vertex (using its position and time)
      float noise = snoise(pos * 0.5 + vec3(0.0, 0.0, time * 0.3));
      // Displace vertex along its normal
      pos += normal * noise * distortion * (1.0 + audioLevel);
      // Standard transformation
      gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0);
    }
  `,
  fragmentShader: `
    uniform vec3 color;
    uniform float audioLevel;
    varying vec3 vNormal;
    varying vec3 vPosition;
    
    void main() {
      // Calculate fresnel (view-angle dependent) term
      vec3 viewDir = normalize(cameraPosition - vPosition);
      float fresnel = 1.0 - max(0.0, dot(viewDir, vNormal));
      fresnel = pow(fresnel, 2.0 + audioLevel * 2.0);
      // Make the fragment color brighter on edges (fresnel) and pulse it slightly with time
      float pulse = 0.8 + 0.2 * sin(time * 2.0);
      vec3 emissiveColor = color * fresnel * pulse * (1.0 + audioLevel * 0.8);
      // Alpha fade out a bit when audio is high (to make spikes more ethereal)
      float alpha = fresnel * (0.7 - audioLevel * 0.3);
      gl_FragColor = vec4(emissiveColor, alpha);
    }
  `
});

In this shader, snoise is a Simplex noise function (not shown above) producing values ~-1 to 1. The vertex shader uses it to offset each vertex (pos += normal * noise * …). We multiply the noise by (1.0 + audioLevel) so that when audioLevel rises, the displacement increases. The distortion uniform is controlled by a slider in the UI, so the user can manually dial the overall spikiness. The fragment shader calculates a fresnel factor to make the wireframe edges glow. Notice how audioLevel factors into the power and into the final color intensity – louder audio makes the fresnel exponent higher (sharper glow) and also increases brightness a bit. We also included a gentle pulsing (sin(time)) independent of audio, just to give a constant breathing motion.

For the inner glow sphere, we used a separate ShaderMaterial: it’s basically a sphere drawn with side: THREE.BackSide (so we see the inner surface) and Additive Blending to give a blooming halo. Its fragment shader also uses a fresnel term, but with a much lower alpha so it appears as a soft haze around the orb. The inner sphere’s size is slightly larger (I used about 1.2× the radius of the outer sphere) so that the glow extends beyond the wireframe. When combined, the outer and inner shaders create the effect of a translucent, energy-filled orb whose surface ripples with music.

To tie it all together, every frame in the render loop I update the shader uniforms with the current time and audio level:

// in the animation loop:
outerMaterial.uniforms.time.value = elapsedTime;
outerMaterial.uniforms.audioLevel.value = audioLevel;
outerMaterial.uniforms.distortion.value = currentDistortion; 
glowMaterial.uniforms.time.value = elapsedTime;
glowMaterial.uniforms.audioLevel.value = audioLevel;

The result is a 3D object that truly feels alive with the music, it oscillates, pulses, and glows in sync with whatever track is playing. Even the one you add.

Animations and Interactions with GSAP

With the visuals reacting to sound, I added GSAP to handle smooth animations and user interactions. GSAP is great for creating timeline sequences and tweening properties with easing, and it also comes with plugins that were perfect for this project: Draggable for click-and-drag UI, and InertiaPlugin for momentum. Best of all, every GSAP plugin is now completely free to use. Below are the key ways I used GSAP in the project:

Intro Animation & Camera Movement: When the user selects a track and hits play, I trigger a brief “activation” sequence. This involves some text appearing in the “terminal” and a slight camera zoom-in toward the orb to signal that the system is online. The camera movement was done with a simple GSAP tween of the camera’s position. For example, I defined a default camera position and a slightly closer “zoomed” position. On play, I use gsap.to() to interpolate the camera position to the zoomed-in coordinates, and on pause/stop I tween it back out. GSAP makes this kind of 3D property animation straightforward:

const defaultCameraPos = { x: 0, y: 0, z: 10 };
const zoomedCameraPos = { x: 0, y: 0, z: 7 }; // move camera closer on zoom

function zoomCameraForAudio(zoomIn) {
  const target = zoomIn ? zoomedCameraPos : defaultCameraPos;
  gsap.to(camera.position, {
    x: target.x,
    y: target.y,
    z: target.z,
    duration: 1.5,
    ease: "power2.inOut"
  });
}

// When audio starts:
zoomCameraForAudio(true);
// When audio ends or is stopped:
zoomCameraForAudio(false);

This smooth zoom adds drama when the music kicks in, drawing the viewer into the scene. The power2.inOut easing gives it a nice gentle start and stop. I also used GSAP timelines for any other scripted sequences (like fading out the “Analyzing…” overlay text after a few seconds, etc.), since GSAP’s timeline control is very handy for orchestrating arranging multiple animations in order.

Draggable UI Panels: The interface has a few UI components overlaying the 3D canvas – e.g. an “Anomaly Controls” panel (with sliders for rotation speed, distortion amount, etc.), an “Audio Spectrum Analyzer” panel (showing a bar graph of frequencies and track selection buttons), and a “System Terminal” readout (displaying log messages like a console). To make the experience playful, I made these panels draggable. Using GSAP’s Draggable plugin, I simply turned each .panel element into a draggable object:

Draggable.create(".panel", {
  type: "x,y",
  bounds: "body",         // confine dragging within the viewport
  inertia: true,          // enable momentum after release
  edgeResistance: 0.65,   // a bit of resistance at the edges
  onDragStart: () => { /* bring panel to front, etc. */ },
  onDragEnd: function() {
    // Optionally, log the velocity or other info for fun
    console.log("Panel thrown with velocity:", this.getVelocity());
  }
});

Setting inertia: true means when the user releases a panel, it will continue moving in the direction they tossed it, gradually slowing to a stop (thanks to InertiaPlugin). This little touch makes the UI feel more tactile and real – you can flick the panels around and they slide with some “weight.” According to GSAP’s docs, Draggable will automatically handle the physics when inertia is enabled , so it was plug-and-play. I also constrained dragging within the body bounds so panels don’t get lost off-screen. Each panel has a clickable header (a drag handle area), set via the handle option, to restrict where a user can grab it. Under the hood, InertiaPlugin calculates the velocity of the drag and creates a tween that smoothly decelerates the element after you let go, mimicking friction.

Interactive Orb Drag (Bonus): As a creative experiment, I even made the 3D anomaly orb itself draggable. This was a bit more involved since it’s not a DOM element, but I implemented it by raycasting for clicks on the 3D object and then rotating the object based on mouse movement. I applied a similar inertia effect manually: when you “throw” the orb, it keeps spinning and slowly comes to rest. This wasn’t using GSAP’s Draggable directly (since that works in screen space), but I did use the InertiaPlugin concept by capturing the drag velocity and then using an inertial decay on that velocity each frame. It added a fun way to interact with the visualizer – you can nudge the orb and see it respond physically. For example, if you drag and release quickly, the orb will continue rotating with momentum. This kind of custom 3D dragging is outside the scope of a basic tutorial, but it shows how you can combine your own logic with GSAP’s physics concepts to enrich interactions.

In summary, GSAP handles all the non-audio animations: the camera moves, panel drags, and little transitions in the UI. The combination of sound-reactive shader animations (running every frame based on audio data) and event-based GSAP tweens (triggered on user actions or certain times) gives a layered result where everything feels responsive and alive.

UI and Atmosphere

Finally, a few words about the surrounding UI/atmosphere which glue the experience together. The visualizer’s style was inspired by sci-fi control panels, so I leaned into that:

Control Panels and Readouts: I built the overlay UI with HTML/CSS, keeping it minimalistic (just semi-transparent dark panels with light text and a few sliders/buttons). Key controls include rotation speed (how fast the orb spins), resolution (tessellation level of the icosahedron mesh), distortion amount, audio reactivity (scaling of audio impact), and sensitivity (which adjusts how the audio’s volume is interpreted). Changing these in real-time immediately affects the Three.js scene – for example, dragging the “Resolution” slider rebuilds the icosahedron geometry with more or fewer triangles, which is a cool way to see the orb go from coarse to finely subdivided. The “Audio Spectrum Analyzer” panel displays a classic bar graph of frequencies (drawn on a canvas using the analyser data) so you have a 2D visualization accompanying the 3D one. There’s also a console-style terminal readout that logs events (like “AUDIO ANALYSIS SYSTEM INITIALIZED” or the velocity of drags in a playful GSAP log format) to reinforce the concept of a high-tech system at work.

Design elements: To boost the sci-fi feel, I added a subtle grid overlay across the whole screen. This was done with pure CSS – a pair of repeating linear gradients forming horizontal and vertical lines (1px thin, very transparent) over a transparent background . It’s barely noticeable but gives a technical texture, especially against the glow of the orb. I also added some drifting ambient particles (tiny dots) floating slowly in the background, implemented as simple divs animated with JavaScript. They move in pseudo-random orbits.

Soundtrack: I curated three atmospheric and moody tracks, along with one of my own unreleased tracks, under my music alias LXSTNGHT. The track was produced in Ableton, and it’s unfinished. The end result is an experience where design, code, and music production collide in real time.

Bringing all these elements together, the final result is an interactive art piece: you load a track, the “Audio ARK” system comes online with a flurry of text feedback, the ambient music starts playing, and the orb begins to pulse and mutate in sync with the sound. You can tweak controls or toss around panels (or the orb itself) to explore different visuals.

The combination of Three.js (for rendering and shader effects), Web Audio API (for sound analysis), and GSAP (for polished interactions) showcases how creative coding tools can merge to produce an immersive experience that engages multiple senses.

And that’s a wrap, thanks for following along!