TouchDesigner GLSL Shader Writing

Write GLSL shaders optimized for TouchDesigner's shader operators.

Quick Start

Every TouchDesigner pixel shader needs:

// 1. Uniforms - Only declare what YOU need
uniform float uTime;

// 2. Output - Must be global, before main()
out vec4 fragColor;

// 3. Main function
void main() {
    vec4 color = texture(sTD2DInputs[0], vUV.st);
    fragColor = TDOutputSwizzle(color);
}

Critical Rules

1. Output declaration: out vec4 fragColor; must be global (before main())
2. Never declare: sTD2DInputs[], vUV, vP, vN - TouchDesigner provides these
3. Always use: TDOutputSwizzle() for final output
4. Uniforms workflow: Declare in GLSL + Configure in TD parameter pages

Automatic Variables (DO NOT Declare)

sTD2DInputs[0]     // Input textures - just use them!
vUV.st             // UV coordinates (0-1)
vP, vN, vColor     // Position, normal, vertex color

Must Declare and Configure

TouchDesigner does NOT provide automatic uniforms. You must:

1. Declare in shader: uniform float uTime;
2. Configure in TD UI (Vectors page):
   • Name: uTime
   • Type: float
   • Value: absTime.seconds

Common Patterns

See examples/PATTERNS.md for ready-to-use templates:

• Basic texture sampling
• Time-based animation
• Multi-input blending
• Generative patterns
• Feedback loops
• Displacement effects

TouchDesigner Functions

// Output (required)
TDOutputSwizzle(vec4 color)

// Noise
TDSimplexNoise(vec2 p)
TDPerlinNoise(vec3 p)

// Color conversion
TDHSVToRGB(vec3 hsv)
TDRGBToHSV(vec3 rgb)

Response Format

When providing shaders, always include:

1. GLSL Code with comments
2. TouchDesigner Setup instructions:
   • Which parameter page (Vectors, Colors, CHOP Uniforms)
   • Uniform names and types
   • Values or expressions (e.g., absTime.seconds)

Common Errors

See reference/TROUBLESHOOTING.md for solutions to:

• 'fragColor' : undeclared identifier
• 'sTD2DInputs' : redefinition
• 'uTime' : undeclared identifier
• Uniforms with no effect
• Black/incorrect output

Additional Resources

• reference/FUNCTIONS.md - Complete API reference
• reference/BEST-PRACTICES.md - Optimization & organization
• examples/COMPLETE.md - Full shader examples

Writing Process

1. Start with basic template
2. Add uniforms (declare + configure)
3. Implement shader logic
4. Test incrementally
5. Optimize when working