Yusuf's Thoughts

Volumetric Audio Nebula

3 min read

A slow, glowing cloud of thousands of points, drifting in 3D space and breathing with the music: bass pushes the cloud outward, highs make it sparkle. It is the perfect ambient loop for a date night, a quiet gallery room, or a screen behind a couch. Built on the GPU POP family so it stays smooth at high point counts.

Before You Start

  • Helpful background: POPs and Audio Reactivity.
  • Any audio source works: a track on disk, system audio, or a microphone.

1. Build the Point Cloud

  1. Add a Noise POP or a Grid/Sphere POP to scatter a few thousand points into a rough sphere.
  2. Add a second Noise POP to offset positions with smooth 3D turbulence so the cloud looks gaseous rather than geometric.
  3. Animate the noise offset slowly over time so the nebula always drifts.

Start modest

Begin with around 50k points. POPs scale to millions, but get the look right first, then crank the count for the final piece.

2. Get the Audio Bands

  1. Add an Audio File In CHOP (or Audio Device In) for your track.
  2. Add an Audio Spectrum CHOP to split it into frequency bins.
  3. Make three averages with Math/Analyze CHOPs: BASS, MID, HIGH. Smooth each with a Lag CHOP (bass slow, highs fast).

3. Make It React

  1. Breathing: Bind BASS to the radius of the cloud (multiply each point’s position outward). Bass hits push the nebula outward, then it eases back.
  2. Sparkle: Bind HIGH to point brightness or size so cymbals and hi-hats glitter across the cloud.
  3. Swirl: Bind MID to the rotation speed or the turbulence amplitude for gentle internal motion.

4. The Glow

  1. Render the points with additive blending so overlapping points build up light.
  2. Colour points by their distance from the centre (a POP position-to-colour map) for an iridescent core-to-edge gradient.
  3. Add a strong Bloom TOP and a faint lens distortion. Slow camera orbit. Done.

Troubleshooting

  • “It reacts too violently / strobes.” - Increase the Lag on the audio channels, especially bass. You want a swell, not a flicker.
  • “The points look flat and digital.” - Add more turbulence, vary point size slightly per point, and lean on additive bloom.
  • “Frame rate drops at high counts.” - Keep everything in POPs (GPU); avoid converting to SOPs. Reduce bloom resolution before reducing point count.

Next Steps

  • FFT colour: Map different frequency bands to different hues so the cloud changes colour with the song’s texture.
  • Beat bursts: Detect onsets to fire occasional shockwaves through the cloud.
  • Inside a splat: Place the nebula inside a Gaussian splat scene for a magical hybrid space.

Parameter Tuning & Behavior

ParameterBehavior
Bass → radiusHigher = dramatic inhale/exhale; Lower = subtle pulse.
Bass lagSlower = smooth swelling; Faster = punchy, percussive.
High → sparkleHigher = glittery and busy; Lower = calm and ambient.
Point countHigher = dense, luminous nebula; Lower = sparse, starry.

Network Architecture

[ AUDIO ]                      [ Audio File In CHOP ]
                                      │
                                      ▼
                               [ Audio Spectrum CHOP ]
                                      │
                          ┌───────────┼───────────┐
                          ▼           ▼           ▼
                       [ BASS ]    [ MID ]    [ HIGH ]   (each + Lag)
                          │           │           │
[ GEOMETRY ]   [ Sphere/Noise POP ] ──┼───────────┤
                          │           │           │
                          ▼           ▼           ▼
                  radius×BASS   swirl×MID   size/bright×HIGH
                          │
                          ▼
[ COLOUR ]            [ position-to-colour POP ]
                          │
                          ▼
[ RENDER ]            [ Render TOP (additive) ] ◀── [ Camera (slow orbit) ]
                          │
                          ▼
[ OUT ]               [ Bloom ] ──▶ [ Lens distortion ] ──▶ [ OUT ]

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