Yusuf's Thoughts

Audio Terrain Generator

5 min read

Build a 3D landscape whose mountains rise and fall with the volume of the music while the terrain scrolls forward. The look shows up a lot in concert backdrops and music videos.

Operator Families in this Recipe

  • SOPs (Surface Operators): Building the 3D terrain mesh.
  • CHOPs (Channel Operators): Extracting audio amplitude.
  • TOPs (Texture Operators): Post-processing the render.

Part 1: Build the Grid

  1. Add a Grid SOP.
    • Rows → 50, Columns → 50.
    • Size X → 4, Size Y → 4.
  2. Add a Noise SOP directly after the Grid SOP.
    • Amplitude → 0 for now. We will drive this from audio.
    • Period → 0.8.
    • Right-click the Offset Z parameter → Expression → type absTime.seconds * 0.5. This scrolls the noise field over time, making the terrain appear to move forward.
  3. Connect to a Null SOP named OUT_TERRAIN.

Part 2: Extract Audio Amplitude

  1. Add an Audio Device In CHOP (microphone or system audio).
  2. Add an Analyze CHOP right after it.
    • Function → RMS Power. This converts the audio stream into one number representing loudness per frame (typically 0 to 0.3 for normal speaking).
  3. Add a Math CHOP:
    • Multiply → 5.0. Amplifies the small RMS value into a range that visibly moves the terrain.
  4. Connect to a Null CHOP named AUDIO_AMP.
  1. Select the Noise SOP. Look at its Amplitude parameter.
  2. Make AUDIO_AMP active (click the + icon on it).
  3. Drag the chan1 channel from the AUDIO_AMP viewer onto the Amplitude parameter.
  4. Select CHOP Reference.

The terrain’s height is now driven by volume. Loud bass = tall peaks, silence = flat ground.

Part 4: Render the Scene

  1. Create a Geo COMP. Inside it, connect the SOP chain ending with OUT_TERRAIN to the out1 node.
    • Optional: add a Wire Frame SOP before out1 to show the mesh as clean wireframe lines.
  2. Back in the root network, add a Camera COMP:
    • Translate Z → 3, Rotate X → -30. This looks down at the terrain from a front-low angle.
  3. Add a Light COMP and a Render TOP.
  4. Assign a Constant MAT (bright cyan or green) to the Geo COMP for a classic terrain wireframe look.

Part 5: Post-Processing

  1. Connect the Render TOP to an HSV Adjust TOP.
    • Animate Hue → right-click → Expression → absTime.seconds * 5. Slowly cycles color.
  2. Add a Bloom TOP (Threshold: 0.3, Intensity: 0.7) for glowing grid edges.
  3. Finish with a Null TOP named OUT.

Bonus: Frequency-Specific Terrain (Equalizer Effect)

Instead of overall volume driving uniform height, make each column of terrain respond to a different audio frequency:

  1. Replace the Analyze CHOP chain with: Audio Spectrum CHOP → Resample CHOP (set to 50 samples, matching the Grid’s column count).
  2. Connect the Resample CHOP to a CHOP to TOP. This creates a 50x1-pixel texture where each pixel’s brightness = one frequency band’s amplitude.
  3. Remove the Noise SOP. Replace it with a Displace SOP:
    • SOP input → Grid SOP.
    • Texture input → CHOP to TOP output.
    • Direction → Normal, Scale → 0.5.
  4. Each of the 50 grid columns now rises to the height of its frequency band, so the terrain works as a 3D equalizer.

Troubleshooting

  • “The terrain doesn’t react to music.” Check that AUDIO_AMP is active and the CHOP Reference is properly set on the Noise SOP’s Amplitude parameter. Open the Noise SOP parameters and confirm the Amplitude field shows an expression rather than a plain number.
  • “Terrain moves but barely.” Increase the Multiply on the Math CHOP (try 10 or 20).
  • “Wireframe renders as a solid blob.” Make sure the Wire Frame SOP is inside the Geo COMP and is the last SOP connected to out1.
  • “Noise pattern does not scroll.” Confirm the absTime.seconds * 0.5 expression is on Offset Z of the Noise SOP (not on the Grid SOP).

Next Steps

  • Camera fly-through: Animate Translate Z on the Camera COMP with absTime.seconds * -0.3 to slowly fly through the terrain.
  • Multiple layers: Duplicate the Grid+Noise chain at different Noise Seeds and blend them in a Composite TOP for multi-depth terrain.
  • Color by height: Use a GLSL TOP to colorize the render: low elevations in blue (water), high elevations in white (snow).

Parameter Tuning & Behavior

ParameterBehavior
Grid Rows/ColumnsHigher = finer terrain detail (heavier); Lower = chunky, angular hills.
Noise PeriodHigher = wide, rolling hills; Lower = tight, jagged spikes.
Noise Scroll Speed (expression)Higher multiplier (e.g., * 2.0) = fast-moving terrain; Lower = slow, hypnotic drift.
Math Multiply (audio)Higher = dramatic mountains on loud audio; Lower = subtle, gentle undulation.
Bloom IntensityHigher = neon grid edges; Lower = clean wireframe.

Network Architecture

[ AUDIO ]                            [ TERRAIN ]
Audio Device In                      Grid SOP (50x50)
       │                                    │
       ▼                                    ▼
Analyze CHOP (RMS)                   Noise SOP ◀── Animate Offset Z
       │                             (Amplitude bound to AUDIO_AMP)
       ▼                                    │
Math CHOP (x5)                       Wire Frame SOP
       │                                    │
       ▼                                    ▼
Null (AUDIO_AMP) ──────────────▶  Geo COMP ──▶ Render TOP
                                              │
                                              ▼
                               HSV Adjust ──▶ Bloom TOP ──▶ OUT

(y) Return to Recipes & Projects | (y) Return to TouchDesigner | (y) Return to Home

Graph View

Backlinks