2D Ray Marching — Sphere Tracing & SDF Explainer

This 2D companion strips ray marching down to the mechanic itself, in a plane instead of a 3D shader. A scene made of two real signed-distance functions — a circle and a rounded box, combinable with union, subtract or intersect — is sphere-traced ray by ray from a draggable eye. The left pane colours the plane by the live SDF value and draws a handful of rays with every intermediate step rendered as the safe-distance circle the algorithm actually computed, the classic ray-marching-explainer picture. The right pane turns the same per-ray hit distances into a 1D raycast wall render, so one identical march drives two different views at once.