Interface GridOptions

An "infinite", distance-fading reference grid — the single strongest visual cue that reads as CAD.

Why not GridHelper: it's a fixed-size square of line segments that visibly ends and looks wrong once you pan or zoom past it. Instead we draw one large screen-facing plane and compute the grid in the fragment shader from world coordinates, fading lines out with distance so the edge is never a hard cutoff. The plane is big enough to cover any reasonable view; the fade hides its bounds.

Two line frequencies (minor + major every 10th) give the usual graph-paper depth read. Spacing is in world units (meters — the scene's normalized unit), so a cellSize of 1 = 1m minor cells.