Follow the Tube All the Way

Follow the Tube All the Way

Produce ONE image, 2:3 portrait: a knotted tube on a gradient field. Follow every line. Replace only the FIELDS block; everything after it is fixed.

First — do you have the fields?

If any field below still has braces around it, stop and ask. Put all the questions in one short message, and show the example under each one so they can see the shape of a useful answer. Wait for the replies, then draw. Never fill a brace yourself: a value you invented is a value nobody asked for, and it will look exactly as considered as the ones they did give you.

Ask in whatever language they are writing to you in. Translate the questions and the examples; do not make someone read English to tell you what they want.

The examples are only examples. If someone answers a question, use their answer; never fall back to the example because you prefer it.

If the fields are already filled in, ignore this and carry on.

Fields — replace these five lines only

• The path — how the tube runs: {a named knot or route, and where it enters and leaves}
• The crossings — how many, and which strand is on top at each: {a count, and over or under for each}
• The tube — diameter and surface: {a diameter as a fraction of the frame, and a finish}
• The gradient and the tube's colours: {a ground gradient, and the tube's hues}
• The type: {two or three short lines, and their positions}

The crossing law

A knot is a path with decisions in it. Every place two parts of the tube meet, one is in front and one is behind, and the one behind continues out the other side.

Each crossing named in the fields is drawn as a crossing:

• The near strand passes over, complete and unbroken.
• The far strand is occluded, and reappears on the other side at the correct position and angle to continue its path.
• There is a contact shadow where the near strand passes over the far one.

A reference run of this style produced a beautiful tangle that could not be followed. At some meetings the two strands simply merged, their surfaces flowing into one another with no over and no under. At others the same strand appeared to pass in front at one crossing and behind at the next. The form looked solid and was not.

Trace the tube from where it enters to where it leaves. If you lose it anywhere, that meeting was a merge.

The diameter law

The tube has one diameter along its entire length. It is extruded, not modelled.

The only thing that may change its apparent width is perspective: a loop further away is smaller by exactly as much as its distance requires, and no more. A tube that is fat in the foreground and thin at the back has been drawn by eye.

Compare a front loop with a back loop. Their widths should differ only as much as their depths do.

The surface

• Ribbing runs perpendicular to the axis at every point, and turns with the tube through every bend. Rings, never spirals, unless the fields ask otherwise.
• The ribbing compresses on the inside of a bend and opens on the outside.
• Glossy but not mirrored: a broad soft highlight running along the upper side, following the tube around each curve. No sharp reflections, no chrome, no environment map.

Colour

• The ground is a smooth gradient, as the fields describe, with no banding and no texture.
• The tube cycles through its hues along its length, so colour tells you where you are on the path. The same point on the tube is the same colour wherever it appears in the frame.
• Light comes from within the palette — the tube glows slightly into the ground around it, tightly.
• No fourth hue, no white blowout, no black.

Composition

• The knot occupies the middle two thirds, well clear of the edges, with the ends running out of frame at the positions the fields give.
• A soft contact shadow beneath the whole form.
• Nothing else in the picture: no particles, no rings, no motion streaks, no reflected floor.

Type

• Small, in one light sans, letterspaced, at the positions the fields give.
• Never over the tube.
• Only what the fields supply. No invented studio names, marks, copyright lines or dates.

Never

• ✕ two strands merging instead of crossing
• ✕ a strand that does not reappear correctly on the far side
• ✕ the same strand passing over at one crossing and under at another without the fields saying so
• ✕ a tube whose diameter changes beyond perspective
• ✕ ribbing that runs along the axis, or fails to turn with a bend
• ✕ chrome, mirror reflections or environment maps
• ✕ particles, rings, streaks or a reflected floor
• ✕ type over the form
• ✕ invented studio names or copyright lines

The result

A form you can follow: one tube, one thickness, three crossings each with a clear front and back, and a colour that tells you how far along you have got.