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weld seams
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Merge tiled copies into one continuous shape by marking the boundary edges that should dissolve.
When you replicate a motif into a tiled or arrayed field, each copy keeps its own edges - so where two copies touch, you get a doubled line running down the seam. Weld dissolves those shared boundaries and merges the copies into one continuous region. The trick is telling Weld which edges are copy boundaries (dissolve them) and which are real pattern lines (keep them). That's what seams are for.
A seam is a straight edge you mark to say this is a tile or copy boundary. Marking it explicitly - rather than having Locus guess after the fact - is what makes welding reliable on dense patterns, where guessing used to over-dissolve and punch holes.
Once marked, a seam survives the whole pipeline. It carries through:
- transforms and replication: Rotate, Array, and Array: Directed keep the mark,
- booleans: intersecting a pattern with a seam-marked border marks exactly the border-derived edges, leaving the pattern's own edges alone,
- Polar Warp: a straight radial domain edge stays a seam through the warp,
- realizing node geometry back to the model.
There are a few ways to mark, depending on where your geometry lives.
- On hand-drawn geometry: select a straight segment (or a region, to mark its straight boundary edges) and flip the Seam toggle in the style palette. You can also type Mark as Seam or Remove Seam from the command palette.
- On node-graph geometry: geometry realized from nodes can't be marked by hand, so mark it upstream in the node graph. Select Outer Edges pulls the perimeter of a tiled field (every edge that borders only one tile), and the Mark as Seam node stamps those edges as seams. Feed one into the other and you've marked the whole outline in one move.
To check your work, turn on View > View Seams - every seam-marked edge traces in bright neon green, on both your model and the live node graph preview.
The rule is deliberately strict: Weld dissolves a straight edge only when it's a seam sitting on top of another seam. Everything else survives - unmarked interior pattern lines, arcs and curves (which are never seams), and a seam with no partner, like an outer perimeter. So marking the copy boundaries and only the copy boundaries gives you a clean merge with the perimeter intact and no holes.
The same rule applies to line work. If a tile is drawn as loose segments or open polylines rather than closed regions, a seam segment whose endpoints match exactly one other seam is removed together with its partner - the doubled line down the copy boundary simply goes. There is no region to merge, so nothing else changes: a polyline that contained the seam is left as the runs on either side of it, and unmarked lines, curves, and outer-rim seams with no partner stay exactly as they were.
Tip
The Weld Tol setting is a small slack knob for minor float misalignment between two sides of a seam. Keep it small - it's not a "weld anything" dial. Widening it too far makes unrelated edges collide and breaks the merge.
Note
Groups weld against themselves. A plain group - a tile's fills, a folder of curves - reads as one set of members, so its seams can dissolve against each other and across arrayed copies of it. A group of groups still reads as a list of whole tiles.
For two copies to weld, their shared boundaries have to line up exactly - copy one's right profile has to match copy two's left profile, edge for edge. That only happens when the domain you tile from is axis-aligned and spans a whole number of lattice periods.
A domain drawn even slightly askew is the usual reason a weld does nothing: a tilt of a couple hundredths of a unit can leave the two boundaries a tenth of a unit apart at the outer radius, and nothing that far apart will merge. The fix is to nudge the domain to a true axis-aligned rectangle sized to an exact multiple of the lattice vector. With the domain squared, the copy seams dissolve at the default tolerance and the pattern runs continuously around the ring.
Caution
Confirm against the build Domain squaring matters most for Polar Warp, where copies wrap around a center and small boundary mismatches grow with radius. If a warp weld leaves seams, check the domain rectangle before touching Weld Tol.
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