🔘 Poisson-Disk Sampling: Bridson's Algorithm (2D)

This 2D companion runs the real, grid-accelerated Bridson algorithm step by step on a plain canvas instead of a decorative dot field: a background grid sized r/√2 drives O(1) neighbor checks, an active list of growable points is drawn from at random each step, up to k candidates are tried in the annulus between r and 2r around the chosen point, and the minimum-distance constraint is enforced exactly — no accepted point ever sits closer than r to another. Watching the active list shrink and the grid cells fill in shows why the algorithm terminates in O(n) time instead of the O(n²) cost of naive rejection sampling.