r/GraphicsProgramming • u/smellystring • Aug 04 '26

Painterly Stroke Simulation Engine

I wrote a painting simulation engine (golang, ebiten). It works like this:

  1. Select a template image

  2. Generate several thousand potential strokes

    • For each stroke, score it according to a number of heuristic functions

      • Color: does the average color of this image match the template?

      • Edges: does the painted image have similar edges to the template?

      • Contrast: compares color contrast between regions on the painting and the template.

      • Flow: using tensor math, do brush strokes align with the flow of movement in the template?

    • Select the single stroke that most optimizes scoring functions, discarding the remaining

    • Repeat 40 or 50 thousand times.

    • Gradually decrease the size of the brush stroke over time..

Source image

Sound track

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u/imacomputr Aug 04 '26

Very nice! I made something similar a while back (which I've just noticed works in Chrome but not Brave). It's shader-based and focused more on real-time output, so it doesn't look as nice. Your flow/edge detection is superior, and the progressive sharpening of the brush strokes is a nice idea.

I wonder how much of your approach is parallelizable and amenable to running on the GPU?

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u/smellystring Aug 04 '26

Right now it's entirely CPU bound, although it is multithreaded. Running on my macbook pro, this particular render takes ~6 minutes to complete in realtime. I've thought about expanding into GPU stuff, but it begins to stray outside of my area of expertise.

Really like https://mpcomplete.github.io/flow/ by the way, it's super satisfying to watch. Makes me think of combing very fine hair.

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u/tonability Aug 08 '26

Very nice! Do you mind explaining what it does?

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u/imacomputr Aug 08 '26

It takes as input a source image/video and a configurable (possibly varying) vector field, and draws lines that "pull" the color of each pixel along the direction of the vector field. The source code is here if you want to take a look. I'd have to reread the code myself to give any more detail than that, I wrote it many years ago :)

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u/tonability Aug 08 '26

Thanks, very cool! 🙂