Knot Designer Manual

Getting started

The designer draws knotwork the way the old scribes did: it starts from a plain plait (strands crossing on a grid of dots) and you add breaks that turn the strands back. The drawing is a flat strip of the ring band; its left and right ends join up round the finger.

Pick a starting pattern under Breaks (Chain is a good first try).
Click dots on the drawing to add, turn or remove breaks.
Choose a strand style and width under Strands.
Set the ring size, rims and metal under Export, and press 3D ring to see it on the finger.
Press Blender code, copy it, and build the ring in Blender (see Making it in Blender).

Your design is kept in this browser as you work, so it is still there next time you open the page. Ctrl+Z undoes and Ctrl+Y redoes.

The screen

At the top is the drawing, with the 3D ring below it when it is open. Under them, a row of readings:

Strands: How many separate strands the knot has. One strand is the classic unbroken knot.
Crossings: How many places strands cross, and any that can't follow the chosen over/under rhythm.
Gap: The closest that two strands come without crossing. If it says they touch, make the strands narrower or the turn gap larger.
Ring size: How many repeats go round the ring and how wide the band will be.
Metal: An estimate of the weight (and cost, if you set a price). Blender measures it exactly.

The buttons beside them open the 3D ring (drag to turn, scroll or pinch to zoom, tick Spin to let it turn by itself) and give Undo and Redo.

The controls below are in panels: Layout, Breaks (or Fret), Strands and Export.

Sliders

Every slider has a − button at its left end and a + button at its right. Each press moves the slider one step, which is easier than dragging when you want a small change. A button greys out when the slider is at its end. The value is shown above the slider on the right.

Layout

Knot / Fret: Knotwork with crossing strands, or a fret (key pattern) of straight lines with no crossings. Each keeps its own design while you switch.
Ring band / Closed panel: A ring band wraps: the strands run off one end and back in at the other. A closed panel turns the strands back at all four edges, like a framed knot. On the ring a panel still wraps round.
Length: How many cells long the strip is. With a repeat set it moves in whole repeats.
Rows: How many cells across the band. More rows make a wider band.
Horizontal stretch: Lengthens the diagonals into long sweeps.
Vertical stretch: Below 1 packs the rows closer: a narrower band with less open space.
Corners: Curved rounds the turns. Straight draws every run as a straight line with a sharp point at each turn.
Roundness: Turns straight runs into continuous curves; with Straight corners it cuts the points off instead.

Breaks

Click a dot to add a break, click again to turn it the other way, and a third time to remove it. A horizontal break turns the strands back up or down; a vertical one turns them back left or right. The diamonds on the borders are edge points: the strands run out past the border and back, giving a pointed edge.

Presets: Plait (no breaks), Chain, Links, Steps, Points, Random, Maze and Clear. Changing the length or rows rebuilds a preset to fit.
Maze: Carves a maze through the cells, so the whole repeat is one connected knot. Straight passes and Corridor length change its character; Seed picks a different maze (the arrows step through them, New maze picks one at random). Set the repeat and mirrors first, as they shape the maze.
Repeat every: Each break you click is copied along the band at this spacing.
Mirror: Copies the half you choose over the other half, left/right or top/bottom. With a repeat set, each repeat is mirrored about its own centre.
Change only the dot I click: Ignores repeat and mirrors. Shift-click does the same at any time.
Flip: Turns the whole design over, horizontally or vertically.

Fret patterns

A fret is straight lines on a grid, turning at right angles, with no crossings. Click between two dots to add or remove a line; every repeat changes with it. Presets: Greek key, Double key, Battlement, Random (the outline of a random maze, always one unbroken line with even spacing; Repeat width, Height, Corridor length and Seed control it) and Clear. Tick Border lines for a line above and below. A width of about 50% makes the lines and the spaces between them equal.

Strands

Style: Ribbon: flat-topped bands. Rounded: half-round. Double: two ridges with a groove between. Sharp: a tall knife-edge ridge. Carved: flat-topped strands in a V-carved background (see below).
Width: As a share of a cell. Wider strands leave less background; watch the gap reading, as tight turns close up first.
Turn gap: How far a strand turns back short of a break.
Weave: Over one, under one; or over two, under two, which braids the same strands with a different rhythm. Crossings that can't follow it are counted under the drawing.
Metal, Colour each strand: Only change how the drawing looks.
Show dots and breaks: Untick for a clean picture of the knot.

Carved style

Carved cuts the background away in sloping facets between flat-topped strands, the chip-carved look of a hand-engraved ring. Width sets the flat tops; about 0.3 mm suits it (18% of a 1.7 mm cell). Three more sliders appear:

Flank angle: How steeply the background falls away from each strand, in degrees from flat. Steeper gives narrower, deeper-looking cuts. 31° matches the reference ring.
Carve depth: From the strand tops down to the deepest pockets, in mm. The rims are measured from the strand tops, so they follow it.
Dip under crossings: How far a strand sinks where it passes under another, in mm. 0 leaves the weave flat; 0.2 is subtle. (Not used for frets, which have no crossings.)

A shallow flank angle with a deep carve makes wide pockets that can run into the rims; if the drawing looks crowded, raise the angle or lower the depth.

Ring, rims and metal

Ring size (US): In half sizes, with the inside diameter in mm.
Cell size on the ring: The grid spacing in mm. It is nudged slightly so a whole number of repeats goes round.
Rim width: Each edge's width across the band.
Rim height: Measured from the strand tops: below them, level, or standing proud. Default rims for this style puts both back.
Weigh in, Gold colour: The alloy for the weight, and the colour of the 3D ring.
Price per gram: Your supplier's price for the alloy; the cost appears beside the weight.

Saving and sharing

Save design to a file: Keeps everything, including your price, in a small file you can open again later, on this or another computer, with Open a saved design.
Share link: A link that opens the ring in 3D only (not the designer, weight or price). It holds the design as it is now. Make it on the live site to send it to someone.
Picture: Untick Show dots and breaks, then right-click the drawing and choose Save image as.

Making it in Blender

The exact, printable ring is built by the Blender add-on make_celtic_band.py (Celtic Band Generator).

Install the add-on once: in Blender, Edit > Preferences > Add-ons > Install from Disk, and pick make_celtic_band.py.
In the designer press Blender code, then Copy.
In Blender choose Add > Mesh > Celtic Band. It reads the design from the clipboard and builds the ring.
When it finishes it shows the exact weight in your alloy (and cost, with a price).

Units are millimetres. Each run replaces the ring from the run before. A carved ring takes about half a minute; its surface is simplified to about a twentieth of the triangles, which keeps the file small without any visible change.

Troubleshooting

Strands touch: Narrow the strands, raise the turn gap, or use a larger cell size.
Clashing crossings: The design can't carry Over two, under two everywhere; switch to Over, under or change the breaks.
Blender builds the default ring: The clipboard didn't hold the designer's code. Press Copy again, then run Add > Mesh > Celtic Band.
The 3D ring doesn't appear: It needs an internet connection the first time, to load its 3D library.
Weight differs from Blender's: The designer's figure is an estimate, usually within about 2%.