I wonder if it would help if you looked at gradient of the SDF as well – maybe you could walk further safely if you're not moving in the same direction as the gradient?
AFAIK (I have a similar soft shadows system based on SDFs) the reason the noise issues occur in small gaps is that the distance values become small there so the steps become small and you start ending up in artifact land. The workaround for this is to enforce a minimum step size of perhaps 0.5 - 2.0 pixels (depending on the quality of your SDF) so you don't get trapped like that - the author probably knows but it's not done by their sample code.
Small step sizes are doubly bad because low-spec shader models like WebGL and D3D9 have a limitation on the number of loop iterations, so no matter how powerful your GPU is the step loop will terminate somewhat early and produce results that don't resemble the ground truth.
Same goes for a few of the other images too, but not all of them.
The article would probably benefit from having figure captions below each image stating whether the image is interactive or not.
Or alternatively to figure captions about interactivity, showing some kind of symbol in one of the corners of each of the ones that are interactive. In that case, the intro should also mention that symbol and what it means before any images that have that symbol on it.
This is truly a very clever series of calculations, a really cool effect, and a great explanation of what went into it. I'll admit that I skimmed over some of the technical details because I want to try it myself from scratch... but the distance map is a great clue.
While the methods are similar in that they both ray-march through the scene to compute per-pixel fluence, the algorithm presented in the blog post scales linearly with the number of light sources, whereas Radiance Cascades can handle an arbitrary distribution of light sources with constant time by benefiting from geometric properties of lighting. Radiance Cascades are also not limited to SDFs for smooth shadows.
The demo at the end has bad banding issues (which the article does acknowledge).
It seems like a cheat-ish improvement to both of these would be a blur applied at the end.
Small step sizes are doubly bad because low-spec shader models like WebGL and D3D9 have a limitation on the number of loop iterations, so no matter how powerful your GPU is the step loop will terminate somewhat early and produce results that don't resemble the ground truth.
The article would probably benefit from having figure captions below each image stating whether the image is interactive or not.
Or alternatively to figure captions about interactivity, showing some kind of symbol in one of the corners of each of the ones that are interactive. In that case, the intro should also mention that symbol and what it means before any images that have that symbol on it.
https://mini.gmshaders.com/p/radiance-cascades
https://youtube.com/watch?v=3so7xdZHKxw