AudioLink Integration

Learn how VRSL integrates with AudioLink for audio-reactive lighting effects

Overview

VRSL includes full integration with AudioLink by llealloo, allowing fixtures to react dynamically to music without DMX input. This system provides an alternative control method ideal for club environments and music venues.

AudioLink integration uses the shader implementation for minimal overhead, avoiding CPU-side audio analysis entirely.

Architecture

The AudioLink system operates independently from DMX:

┌──────────────┐
│ Audio Source │
└──────┬───────┘
       │
       ▼
┌──────────────┐
│  AudioLink   │ ◄─── FFT Analysis
│  Component   │      4 Frequency Bands
└──────┬───────┘
       │
       ▼
┌──────────────────┐
│ AudioLink Texture│ ◄─── GPU Texture
│  (Float RGBA)    │      History Buffer
└──────┬───────────┘
       │
       ▼
┌──────────────────┐
│  VRSL Shaders    │ ◄─── Sample & React
│  (AudioLink)     │      Per-fixture
└──────────────────┘

Frequency Band Mapping

AudioLink divides audio into four frequency bands:

Band	Frequency Range	Typical Instruments	VRSL Usage
Bass (0)	0-200 Hz	Kick drum, sub-bass	Intensity, strobe
Low Mids (1)	200-500 Hz	Snare, bass guitar	Color modulation
High Mids (2)	500-2000 Hz	Vocals, guitars	Cone width, effects
Treble (3)	2000+ Hz	Hi-hats, cymbals	Fast strobes, highlights

Band Selection

The VRStageLighting_AudioLink_Static component exposes band selection:

// From VRStageLighting_AudioLink_Static.cs:20-26
public enum AudioLinkBandState
{
    Bass,           // Band 0
    Low_Mids,       // Band 1
    High_Mids,      // Band 2
    Treble          // Band 3
}

Shaders access the selected band:

// VRSL-AudioLink-Functions.cginc:155-158
float getBand()
{
    return UNITY_ACCESS_INSTANCED_PROP(Props, _Band);
}

Amplitude Reading

VRSL samples AudioLink’s amplitude data with optional delay:

// VRSL-AudioLink-Functions.cginc:39-42
inline float AudioLinkLerp3_g5(int Band, float Delay)
{
    return AudioLinkLerp(ALPASS_AUDIOLINK + float2(Delay, Band)).r;
}

The main amplitude function:

// VRSL-AudioLink-Functions.cginc:182-192
float GetAudioReactAmplitude()
{
    if(checkIfAudioLink() > 0)
    {
        return AudioLinkLerp3_g5(getBand(), getDelay()) * getBandMultiplier();
    }
    else
    {
        return 1;  // No reaction when disabled
    }
}

Parameters

Band - Which frequency range to react to (0-3)

Delay - Sample history in frames (0-127)

• Higher values = more “lagged” reaction
• Useful for creating delayed lighting effects
• Stored in AudioLink’s history buffer

Band Multiplier - Sensitivity scaling (1.0-15.0)

• Amplifies weak signals
• Prevents over-saturation of loud music

// VRStageLighting_AudioLink_Static.cs:656-659
props.SetFloat("_Delay", delay);
props.SetFloat("_BandMultiplier", bandMultiplier);
int b = (int) band;
props.SetFloat("_Band", (float)b);

Color Chord Integration

ColorChord analyzes audio for dominant notes and generates colors:

// VRSL-AudioLink-Functions.cginc:194-197
float4 GetColorChordLight()
{
    return AudioLinkData(ALPASS_CCLIGHTS).rgba;
}

Used in emission calculation:

// VRSL-AudioLink-Functions.cginc:199-206
float4 getEmissionColor()
{
    float4 emissiveColor = UNITY_ACCESS_INSTANCED_PROP(Props, _Emission);
    float4 col = enableColorTextureSample ? 
        (averageIntensity * GetTextureSampleColor()) : emissiveColor;
    col = enableThemeColorSampling ? 
        (averageIntensity * GetThemeSampleColor()) : col;
    return checkIfColorChord() == 1 ? GetColorChordLight() * 1.5 : col;
}

ColorChord mode overrides manual color settings and texture sampling, providing musically-driven color changes.

Theme Color Sampling

AudioLink provides four theme colors that can be set by world creators:

// VRSL-AudioLink-Functions.cginc:67-82
float4 GetThemeSampleColor()
{
    switch(UNITY_ACCESS_INSTANCED_PROP(Props, _ThemeColorTarget))
    {
        case 1:
            return AudioLinkData(ALPASS_THEME_COLOR0);
        case 2:
            return AudioLinkData(ALPASS_THEME_COLOR1);
        case 3:
            return AudioLinkData(ALPASS_THEME_COLOR2);
        case 4:
            return AudioLinkData(ALPASS_THEME_COLOR3);
        default:
            return float4(0,0,0,1);
    }
}

Theme colors are set via MaterialPropertyBlock:

// VRStageLighting_AudioLink_Static.cs:648-649
props.SetInt("_EnableThemeColorSampling", enableThemeColorSampling == true ? 1 : 0);
props.SetInt("_ThemeColorTarget", themeColorTarget);

Texture Color Sampling

Fixtures can sample colors from a custom texture:

// VRSL-AudioLink-Functions.cginc:58-65
float4 GetTextureSampleColor()
{
    float4 rawColor = tex2Dlod(_SamplingTexture, 
        float4(UNITY_ACCESS_INSTANCED_PROP(Props,_TextureColorSampleX), 
               UNITY_ACCESS_INSTANCED_PROP(Props,_TextureColorSampleY), 0, 0));
    float4 h = RGBtoHSV(rawColor.rgb);
    h.z = 1.0;  // Full brightness
    return useTraditionalSampling ? rawColor * multiplier : (HSVtoRGB(h) * multiplier);
}

Sampling Modes

Traditional Sampling - Uses raw RGB values from texture

HSV Conversion - Extracts hue only, sets saturation and value to maximum

• Creates pure, vibrant colors
• Consistent brightness regardless of source texture

// VRStageLighting_AudioLink_Static.cs:644-647
props.SetFloat("_TextureColorSampleX", textureSamplingCoordinates.x);
props.SetFloat("_TextureColorSampleY", textureSamplingCoordinates.y);
props.SetInt("_EnableColorTextureSample", enableColorTextureSampling == true ? 1 : 0);
props.SetInt("_UseTraditionalSampling", traditionalColorTextureSampling == true ? 1 : 0);

Component Configuration

The VRStageLighting_AudioLink_Static component manages all AudioLink properties:

AudioLink Settings

// VRStageLighting_AudioLink_Static.cs:37-68
[Header("Audio Link Settings")]

[SerializeField] private bool enableAudioLink;
[SerializeField] private AudioLinkBandState band;
[SerializeField, Range(0, 127)] private int delay;
[SerializeField, Range(1.0f, 15.0f)] private float bandMultiplier = 1.0f;
[SerializeField] private bool enableColorChord;

Property Updates

All changes trigger MaterialPropertyBlock updates:

// VRStageLighting_AudioLink_Static.cs:651-660
//AudioLink Stuff
props.SetFloat("_EnableAudioLink", enableAudioLink == true ? 1.0f : 0.0f);
props.SetInt("_EnableColorChord", enableColorChord == true ? 1 : 0);
props.SetFloat("_Delay", delay);
props.SetFloat("_BandMultiplier", bandMultiplier);
int b = (int) band;
float ba = 1.0f * b;
props.SetFloat("_Band", ba);

AudioLink fixtures can be toggled without DMX, making them ideal for testing or permanent audio-reactive installations.

Intensity Modulation

AudioLink amplitude modulates the final intensity:

// In vertex shader (VRSL-StandardMover-Vertex.cginc:600-603)
o.audioGlobalFinalConeIntensity.x = GetAudioReactAmplitude();
o.audioGlobalFinalConeIntensity.y = getGlobalIntensity();
o.audioGlobalFinalConeIntensity.z = getFinalIntensity();
o.audioGlobalFinalConeIntensity.w = getConeWidth();

Applied in fragment shader:

finalIntensity *= o.audioGlobalFinalConeIntensity.x;  // AudioLink amplitude
finalIntensity *= o.audioGlobalFinalConeIntensity.y;  // Global intensity
finalIntensity *= o.audioGlobalFinalConeIntensity.z;  // Final intensity

Laser Integration

The VRStageLighting_AudioLink_Laser component provides similar functionality for laser effects:

// VRStageLighting_AudioLink_Laser.cs:32-79
[Header("Audio Link Settings")]
private bool enableAudioLink;
private AudioLinkBandState band;
[Range(0, 31)] private int delay;           // Note: Shorter range for lasers
[Range(1.0f, 15.0f)] private float bandMultiplier = 1.0f;
private bool enableColorChord;

Laser-Specific Properties

// VRStageLighting_AudioLink_Laser.cs:150-220
[Range(-3.75f, 20.0f)] private float coneWidth = 2.5f;
[Range(-0.5f, 5.0f)] private float coneLength = 8.5f;
[Range(0.0f, 1.999f)] private float coneFlatness = 0.0f;
[Range(-90.0f, 90.0f)] private float coneXRotation = 0.0f;
[Range(-90.0f, 90.0f)] private float coneYRotation = 0.0f;
[Range(-90.0f, 90.0f)] private float coneZRotation = 0.0f;
[Range(4.0f, 68f)] private int laserCount = 14;
[Range(0.003f, 0.25f)] private float laserThickness = 0.125f;
[Range(-1.0f, 1.0f)] private float laserScroll = 0.0f;

Disabling for DMX Mode

When DMX is enabled, AudioLink can be automatically disabled:

// VRStageLighting_AudioLink_Static.cs:748-756
public void _UpdateInstancedPropertiesSansAudioLink()
{
    // ... other properties ...
    
    //AudioLink Stuff
    props.SetFloat("_EnableAudioLink", 0.0f);
    props.SetInt("_EnableColorChord", 0);
    
    // ... rest of properties ...
}

HSV Color Conversion

For pure hue extraction from textures:

// VRSL-AudioLink-Functions.cginc:5-26
float4 RGBtoHSV(in float3 RGB)
{
    float3 HSV = 0;
    HSV.z = max(RGB.r, max(RGB.g, RGB.b));  // Value
    float M = min(RGB.r, min(RGB.g, RGB.b));
    float C = HSV.z - M;                     // Chroma
    if (C != 0)
    {
        HSV.y = C / HSV.z;                   // Saturation
        float3 Delta = (HSV.z - RGB) / C;
        Delta.rgb -= Delta.brg;
        Delta.rg += float2(2,4);
        if (RGB.r >= HSV.z)
            HSV.x = Delta.b;
        else if (RGB.g >= HSV.z)
            HSV.x = Delta.r;
        else
            HSV.x = Delta.g;
        HSV.x = frac(HSV.x / 6);             // Hue
    }
    return float4(HSV, 1);
}

Performance Considerations

GPU Efficiency

• AudioLink texture is sampled once per fixture per frame
• Minimal ALU cost (single multiply for amplitude)
• No branching in amplitude calculation
• Compatible with GPU instancing

Recommended Settings

For Bass-heavy Music:

• Band: Bass (0)
• Delay: 0-10
• Multiplier: 2.0-5.0

For Melodic Content:

• Band: High Mids (2)
• Delay: 10-30
• Multiplier: 3.0-8.0

For Strobe Effects:

• Band: Treble (3)
• Delay: 0
• Multiplier: 8.0-15.0

High band multipliers with loud music can cause epileptic-triggering strobing. Always test in context and provide user controls.

Example Setup

Configuring an audio-reactive fixture:

1. Add VRStageLighting_AudioLink_Static component
2. Assign mesh renderers to objRenderers array
3. Configure AudioLink settings:
   • Enable AudioLink: ✓
   • Band: Low Mids
   • Delay: 15
   • Band Multiplier: 4.0
4. Set color mode:
   • Enable Color Chord: ✓ (for automatic colors)
   • OR
   • Set Light Color Tint manually
5. Adjust intensity ranges for desired effect

Related Topics

DMX System

Compare with DMX-based control

Shader Architecture

How shaders process AudioLink data