Yusuf's Thoughts

Waveform Oscilloscope

4 min read

Turn live microphone or system audio into a glowing 3D waveform that pulses in real time with every beat, pluck, and breath. This is the visual equivalent of a hardware oscilloscope, and it takes about ten minutes to build.

Operator Families in this Recipe

  • CHOPs (Channel Operators): Capturing audio and generating X positions.
  • SOPs (Surface Operators): Converting CHOP data into 3D geometry.
  • MATs (Materials): Rendering the waveform as a glowing line.

Part 1: Capture the Audio

  1. Press Tab and add an Audio Device In CHOP.
  2. In the parameters, set Device to your microphone or system output.
  3. Click the Viewer flag (eye icon) on the node and speak or play music. You should see the waveform jumping live in the preview.

Part 2: Generate X Positions

CHOP to SOP needs a separate channel to spread points horizontally. We create one with a ramp.

  1. Add a Pattern CHOP.
    • Type → Ramp.
    • From → -0.5, To → 0.5. This spreads points from left to right.
    • Channels → type tx.
    • Samples → 1024.
  2. Add a Resample CHOP after your Audio Device In CHOP.
    • Connect the Resample CHOP to the Audio Device In.
    • Right-click End → Expression → op('pattern1').end. This syncs the audio length to the Pattern CHOP automatically.

Part 3: Merge and Convert to Geometry

  1. Add a Merge CHOP and connect:
    • Input 0: the Resample CHOP (audio, channel named chan1).
    • Input 1: the Pattern CHOP (ramp, channel named tx).
  2. Add a CHOP to SOP after the Merge CHOP.
    • TX → tx (the ramp provides horizontal positions).
    • TY → chan1 (audio amplitude provides vertical positions).
    • TZ → leave blank.

You now have a live polyline tracing the waveform shape.

Part 4: Render It

  1. Create a Geo COMP. Set its SOP path to your CHOP to SOP node (e.g., ../choptoSOP1).
  2. Create a Line MAT and drag it onto the Geo COMP.
    • Line Width → 0.003 for a thin elegant line, or 0.01 for a thick neon stroke.
    • Color → a bright saturated color (e.g., cyan 0, 1, 1).
    • Lighting → Off.
  3. Add a Camera COMP (Translate Z = 2).
  4. Add a Render TOP.

Part 5: Polish

  • Add a Bloom TOP (Threshold: 0.4, Intensity: 0.8) for a glow effect.
  • Add an HSV Adjust TOP and animate Hue → absTime.seconds * 10 for a slow color shift.

Troubleshooting

  • “Flat line - nothing moves.” - Check microphone permissions and ensure Device is set correctly on the Audio Device In CHOP.
  • “Points are stacked vertically, not spread horizontally.” - Check that the Pattern CHOP’s channel name is tx and that CHOP to SOP’s TX field is set to tx.
  • “Waveform disappears when quiet.” - Add a Lag CHOP between the Resample CHOP and the Merge CHOP to add a decaying trail after sound stops.
  • “Geometry is too tall/clips off screen.” - Add a Math CHOP before the Merge (multiply the audio by 0.3) to scale the amplitude down.

Next Steps

  • Spectrum Mode: Replace the raw audio with an Audio Spectrum CHOP to show the frequency spectrum (like a 3D EQ bar chart) instead of the waveform.
  • Reactive Color: Bind an Analyze CHOP (RMS Power) to the Line MAT color so the line brightens on loud hits.
  • 3D Depth: Add a second waveform at a different Z position and composite them together for a stereo display.

Parameter Tuning & Behavior

ParameterBehavior
Pattern From/ToWider range (e.g., -2 to 2) = waveform spans more screen; Narrower = compact, centered display.
Line WidthHigher = thick neon stroke; Lower = delicate hairline.
Bloom IntensityHigher = waveform glows like a laser; Lower = clean, flat line.
Math Multiply (before merge)Higher = more reactive to quiet audio; Lower = prevents clipping on loud signals.
Lag (Smoothing)Higher = smooth, liquid waveform with trails; Lower = raw, every vibration visible.

Network Architecture

[ AUDIO ]                        [ POSITIONS ]
Audio Device In                  Pattern CHOP (tx, 1024 pts)
       │                                 │
       ▼                                 │
Resample CHOP (1024 pts) ──────────────▶ │
                                         ▼
                               Merge CHOP (chan1 + tx)
                                         │
                                         ▼
                               CHOP to SOP (TX=tx, TY=chan1)
                                         │
                                         ▼
                   Geo COMP (Line MAT) ──▶ Render TOP ──▶ Bloom ──▶ OUT

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