Mastering GLSL in TouchDesigner, Lesson 11: Convolution Kernels

In this lesson of Mastering GLSL in TouchDesigner, we explore convolution kernels, a powerful technique for image filtering that allows for effects like sharpening, edge detection, embossing, and Gaussian blur. You’ll learn how convolution matrices modify pixel neighborhoods and how to implement multi-pass filtering for dynamic effects.

📌 Key Topics Covered:
✅ Understanding convolution kernels and how they alter images
✅ Implementing sharpening, edge detection, and motion blur
✅ Using mipmaps and textureLod() for efficient sampling
✅ Applying multiple shader passes for more complex effects

🎨 Exercises & Challenges:
🛠️ Implement a custom convolution kernel from scratch
🛠️ Build a CRT effect with vignette, scanlines, and chromatic aberration
🛠️ Create a unique effect by combining multiple filtering techniques

Explanation of kernels with some good illustrations: https://medium.com/@timothy_terati/image-convolution-filtering-a54dce7c786b
Interactive convolution kernel explorer: https://setosa.io/ev/image-kernels/

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00:00 – Start
00:04 – Intro: Advanced Image Filters with GLSL
01:08 – Image Convolution Kernel
09:49 – Implementing kernels in GLSL
12:11 – Mipmaps
16:39 – Convolve TOP
17:56 – Begin TouchDesigner Examples
19:08 – TextureLOD
22:36 – Edge Detection (Sobel Filter) in GLSL
27:33 – Sharpen Filter
31:30 – Emboss
32:34 – Barrel Blur GLSL TouchDesigner
34:24 – Exercises