Hough Circles
cv::HoughCircles is an OpenCV function that detects circles in an image using the Hough Circle Transform (based on the gradient method).
Download TouchDesigner version on my Patreon
It is fast and quite reliable when edge detection is clean, but it is very sensitive to parameter tuning:
- minDist — minimum distance between detected circle centers; too small produces duplicates, too large misses neighbors.
- param1 — upper Canny edge threshold; controls how strong an edge must be to count.
- param2 — accumulator threshold; lower values find more (and more false) circles.
- minRadius / maxRadius — the radius range to search in.
ScriptOP using TOP texture as input and output lines coordinates as CHOP:
A Script OP receives any TOP texture — a camera, video file, or rendered image — converts it to grayscale, runs cv::HoughCircles on each frame, and outputs the center coordinates and radius of every detected circle as CHOP channels. From there the data can drive instancing, geometry, or sound: detected circles in the real world become control signals for a generative system.
Use cases
- Abstract visuals — circles found in everyday footage (eyes, lights, wheels, cups) become the raw material for minimal geometric compositions.
- Interactive installations — physical round objects act as controllers for real-time graphics.
- Machine vision studies — visualizing how detection quality reacts to parameters and lighting.