Celtic Knot Shapes

Upload an SVG of a shape (a cross, a circle, a shield, a letter) and the knotwork is woven to fill it. Click a dot to add a break, click again to turn it, a third time to remove it. Download the result as an STL for printing or casting. User manual

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Scroll to zoom, drag to move, Ctrl-drag a strand to bend it. Esc to finish.

Loading the 3D view…

Drag to turn, right-drag to move, scroll to zoom.
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Shape

The shape is whatever the SVG draws: filled areas and lines alike. If it's a line drawing of an outline, tick Fill inside closed lines.

Panels

Click inside a panel on the drawing to select it; shift-click to add or remove one; click outside them all to select none, so changes apply to every panel. Linked panels share one pattern, turned so each reads outward from the panel they meet. Shapes of the same colour in the SVG start linked.

Layout

Double-armed spirals: the strand winds in along one arm, turns at the eye and winds out along the other. S joins two turning the same way, C two mirror images, Triple three round the middle (a triskele). The strands take the panel's Strands settings; the cells and breaks below are for knots.

Fill to the outline moves the strands' turns at the edge out until they almost touch the outline (or the rim), closing the gaps the cells leave. The gap at the outline then sets how close they come.

Breaks

One strand adds breaks until the whole knot is a single strand, then sprinkles in more where they keep it that way. Random just sprinkles. Mirrors and turns shape both; with them on, a few strands may remain.

Mirrors copy each break you click across the middle of the shape. Shift-click changes one dot at any time.

Hold Ctrl (⌘ on a Mac) and drag a strand to move it from that point; crossings move both strands through them. Changing the cells puts moved strands back.

Strands

Carved: flat-topped strands with the background cut away in sloping facets, like the carved ring. Width sets the flat tops; about 0.3 mm suits it.

Emblem

Backing plate

3D and export

Woven on the back needs the backing plate off (with panels, it applies to those without one).

For Blender: install make_knot_shape.py as an add-on, then Copy for Blender and choose Add > Mesh > Celtic Knot Shape. It builds the same design at full detail, with a fused print solid and the exact weight.

The STL is in millimetres. Strands overlap where they cross; slicers and casting services merge them, and Blender can join them with a Union.