hermes-agent/skills/creative/touchdesigner-mcp/references/postfx.md

# Post-FX Reference

Bloom, CRT scanlines, chromatic aberration, and feedback glow patterns for live visual work.

---

## Bloom

### Built-in Bloom TOP

TD's `bloomTOP` is the fastest path — GPU-accelerated, no shader needed.

```python
bloom = root.create(bloomTOP, 'bloom1')
bloom.par.threshold = 0.6     # Luminance threshold (0-1)
bloom.par.size = 0.03         # Spread radius (0-1)
bloom.par.strength = 1.5      # Bloom intensity
bloom.par.blendmode = 'add'   # 'add' or 'screen'
```

**Audio reactive bloom:**
```python
bloom.par.strength.mode = ParMode.EXPRESSION
bloom.par.strength.expr = "op('audio_env')['envelope'][0] * 3.0 + 0.5"
```

### GLSL Bloom (More Control)

For multi-pass bloom with color tinting:

```glsl
// bloom_pixel.glsl — pass1: threshold + tint
out vec4 fragColor;
uniform float uThreshold;
uniform vec3 uBloomColor;

void main() {
    vec4 col = texture(sTD2DInputs[0], vUV.st);
    float luma = dot(col.rgb, vec3(0.299, 0.587, 0.114));
    float bloom = max(0.0, luma - uThreshold);
    fragColor = TDOutputSwizzle(vec4(col.rgb * bloom * uBloomColor, col.a));
}
```

Then blur with `blurTOP` (size ~0.02-0.05), composite back over source with `addTOP` or `compositeTOP` in Add mode.

---

## CRT / Scanlines

Pure GLSL — create a `glslTOP` and paste into its `_pixel` DAT.

```glsl
// crt_pixel.glsl
out vec4 fragColor;
uniform float uTime;
uniform float uScanlineIntensity;  // 0.0 - 1.0, default 0.4
uniform float uCurvature;          // 0.0 - 0.15, default 0.05
uniform float uVignette;           // 0.0 - 1.0, default 0.8

vec2 curveUV(vec2 uv, float amount) {
    uv = uv * 2.0 - 1.0;
    vec2 offset = abs(uv.yx) / vec2(6.0, 4.0);
    uv = uv + uv * offset * offset * amount;
    return uv * 0.5 + 0.5;
}

void main() {
    vec2 res = uTDOutputInfo.res.zw;
    vec2 uv = vUV.st;

    // CRT barrel distortion
    uv = curveUV(uv, uCurvature * 10.0);

    // Kill pixels outside curved screen
    if (uv.x < 0.0 || uv.x > 1.0 || uv.y < 0.0 || uv.y > 1.0) {
        fragColor = vec4(0.0, 0.0, 0.0, 1.0);
        return;
    }

    vec4 col = texture(sTD2DInputs[0], uv);

    // Scanlines
    float scanline = sin(uv.y * res.y * 3.14159) * 0.5 + 0.5;
    col.rgb *= mix(1.0, scanline, uScanlineIntensity);

    // Horizontal noise flicker
    float flicker = TDSimplexNoise(vec2(uv.y * 100.0, uTime * 8.0)) * 0.03;
    col.rgb += flicker;

    // Vignette
    vec2 vig = uv * (1.0 - uv.yx);
    float v = pow(vig.x * vig.y * 15.0, uVignette);
    col.rgb *= v;

    fragColor = TDOutputSwizzle(col);
}
```

---

## Chromatic Aberration

Splits RGB channels and offsets them along screen axes.

```glsl
out vec4 fragColor;
uniform float uAmount;   // 0.001 - 0.02, default 0.006

void main() {
    vec2 uv = vUV.st;
    vec2 dir = uv - 0.5;

    float r = texture(sTD2DInputs[0], uv + dir * uAmount).r;
    float g = texture(sTD2DInputs[0], uv).g;
    float b = texture(sTD2DInputs[0], uv - dir * uAmount).b;
    float a = texture(sTD2DInputs[0], uv).a;

    fragColor = TDOutputSwizzle(vec4(r, g, b, a));
}
```

**Audio-reactive variant** — spike aberration on beats:
```glsl
uniform float uBeat;
void main() {
    vec2 uv = vUV.st;
    vec2 dir = uv - 0.5;
    float amount = uAmount + uBeat * 0.04;
    float r = texture(sTD2DInputs[0], uv + dir * amount * 1.2).r;
    float g = texture(sTD2DInputs[0], uv).g;
    float b = texture(sTD2DInputs[0], uv - dir * amount * 0.8).b;
    fragColor = TDOutputSwizzle(vec4(r, g, b, 1.0));
}
```

---

## Feedback Glow

Warm persistent trails for glow effects.

```glsl
out vec4 fragColor;
uniform float uDecay;     // 0.92 - 0.98 for slow trails
uniform vec3 uGlowColor;  // tint accumulated feedback

void main() {
    vec2 uv = vUV.st;
    vec4 prev = texture(sTD2DInputs[0], uv);  // feedback input
    vec4 curr = texture(sTD2DInputs[1], uv);  // current frame

    vec3 glow = prev.rgb * uDecay * uGlowColor;
    vec3 result = max(glow, curr.rgb);

    fragColor = TDOutputSwizzle(vec4(result, 1.0));
}
```

**Tips:**
- `uDecay = 0.95` → medium trail
- `uDecay = 0.98` → long comet tail
- Set `glslTOP` format to `rgba16float` for smooth gradients

---

## Full Post-FX Stack

Recommended order:

```
[scene / composite]
        ↓
   bloomTOP          ← luminance threshold bloom
        ↓
   glslTOP (chrom)   ← chromatic aberration
        ↓
   glslTOP (crt)     ← scanlines + barrel distortion + vignette
        ↓
   null_out          ← final output
```

**Performance note:** Each glslTOP is a full GPU pass. For 1920×1080 at 60fps this stack is comfortably real-time. For 4K, consider downsampling bloom input with `resolutionTOP` first.