Interlacing

Drawing a frame in two passes of alternating lines, a trick from broadcast. Efficient once, an artefact now.

Interlacing was broadcast's clever poverty: draw every other line, then the rest, and let the eye fuse two half-pictures into one. It doubled apparent motion within starved bandwidth, and an era of television was built on the flicker of alternating fields.

Efficient once, an artefact now: modern screens draw complete frames, and interlaced material shows its seams as combing on motion, teeth along every moving edge. The term survives in the small p of 1080p, progressive, meaning whole frames, and in archival work, where deinterlacing old footage respectfully is its own quiet craft.