Tying-vector build bible

A still is ready when it answers

1. Which strand goes over?
2. Which strand goes under?
3. Which end is moving?
4. Which part stays still?
5. Where does the tag enter, and where does it emerge?
6. What opening is the aim?
7. What changed in this move?
8. What should the structure look like when the move is complete?

How a move is drawn

Authored 3D sequence, then compile, then blend along material coordinate u, then project, then crossing cuts, then SVG. The path is never morphed. Over and under at time t is whatever the 3D pose says.

• wrap — turns form from the standing side of the active range toward the tag.
• pass / tuck / feed — the free end leads.
• tighten — the working range cinches together. Hardware that has not moved stays frozen.

Shot list

1. Hold pose A until standing versus tag is obvious.
2. Mark the opening on a pass or tuck while t is below 0.75.
3. Move only the working range.
4. Keep crossings valid mid-travel. The under-strand disappears and re-emerges.
5. Settle on pose B and drop temporary cues.
6. Hold until “You should now see” matches the picture.

Do not use path-reveal as the only motion, a whole-knot morph, zoom as tighten, arrows painted on the rope, or photoreal gloss.

Sizes

• Thumb — silhouette and crossings. No labels.
• Card — structural reading, callouts, halo. The live tie-player size.
• Plate — full instructional stills with tag and standing labels.

Timing at 1×: 1400 ms travel, 1800 ms hold. Speeds 0.5 / 1 / 1.5. The camera holds the union of the start and end frames. Mirror flips geometry, never labels. Reduced motion snaps to the resolved pose.