OpenNest/docs/geometry/expand-spacing.md

Expand Spacing

Plate > Expand Spacing moves selected parts by translation only. The first selected part is the anchor for selected pairs; the later selected member moves, and nonselected parts remain fixed. The plate retains its own EdgeSpacing floor; the command does not change PartSpacing or EdgeSpacing.

Repeating patterns

A selection that repeats on a lattice, such as a fill, is stretched as one pattern instead of going through the pair search below. Parts of one drawing at one rotation form a motif group, and every group must sit on the same two lattice translations (one for a single row) to within 2% of a pitch. Each group needs at least two parts, and one group needs at least three for a row or four for a grid, because any two or three points fit some lattice. A single-drawing selection that fits no one lattice also counts when it forms rows along X (or Y): at least two rows of at least two parts, one of at least three, whose steps along the row are whole multiples of one shared pitch. Such rows may stack at any spacing and offset, as when staggered rows are topped by straight ones, and each part then stretches on its own. Cut-offs, overlapping selections and selections that start outside the work area always use the pair search.

The lattice is scaled along X, then along Y, about its center, and each part moves by the displacement of its motif copy's lattice point, so interlocked pairs and other multi-part motifs stay rigid. Along each axis the largest scale is used whose stretched selection fits the work area and keeps every floor: no selected gap closes below the smallest selected gap at entry, a gap to a nonselected part closes no further than that, and cut-offs and clamps keep their entry gaps. A part may not pass through a nonselected part, cut-off or clamp on its straight way from the entry layout. The stretched selection is tried centered on where it was, then held at its low edge, then at its high edge. An axis with no room keeps its pitch, so a fill whose rows run edge to edge along X only opens its rows along Y: the row gap stays and the diagonal gap grows. The status bar reads "Spread the repeating pattern" with the smallest gap, or says the pattern has no room to spread.

Every selected/selected and selected/nonselected pair has a clearance floor, measured against material with cutouts subtracted. A pair of parts may close to the spacing being tried but never below its own starting gap when that gap is already smaller, so a wide gap can be spent evenly across a layout and a tight one cannot shrink. A cut-off or clamp always keeps its full starting gap. A later move may reuse slack opened by an earlier move. Existing overlaps are accepted for attempted separation; a remaining overlap is reported as a violation, not a successful positive gap. Geometry whose material side is unresolved at sub-scale is conservatively reported as a violation when native extents intersect; that negative marker is not a measured penetration depth. An unchanged selected part already outside the work area also yields an edge violation and zero credited spacing. Temporarily blocked pairs are retried after another part moves, while a pass without positive movement stops the relaxation. An individual violation's BlockedByEdge flag is true only when the work-area edge is the first limiting cause; the desktop status currently displays a blocked-pair count, not those individual causes.

Probes run on scratch poses. Each trial translation is clipped against blocking material along its entire straight path, including cutout walls and regenerated open cut-off paths; a remote cut-off does not pin an unrelated move. Entry floors for open cut-offs use nearest points on every native segment, not a program endpoint or a fictional closing chord. Open paths that strictly enter part material stay as violations even at zero target; boundary contact and paths wholly inside holes remain legal. An open path's broad box is not a blocker when its real segments miss the part. Initially overlapping convex line profiles and complete native disks can take a certified direct separating path, including a safe partial move when the plate edge prevents a full exit; unsupported or ambiguous overlap paths stay put and remain reported. Complete native disks use analytic clearance rather than interpreting a shallow arc overlap as a positive polygon gap. For other curved pairs, a polygon gap inside the combined 0.002-unit chord band is uncertain and conservatively reported as a violation rather than proof of clear material. When a part touches a cutout wall and the usual nearest-boundary direction makes no safe progress, the tool tries the opposite direction through the same checks. Tiny clamp keep-outs use tolerance-free material occupancy and a conservative native-bound motion limit when tolerant geometry cannot certify them. Cancellation before application leaves the live layout unchanged; Separate never changes it. A bounded search reports the spacing it found, not an optimum. See directional slides for directional contact behavior.

Canceling a long search

On a complex layout the search can run for minutes. The desktop command runs it on a worker thread; if it is still running after about 0.3 seconds, a small Expand Spacing window opens with an elapsed time and a Cancel button, and the rest of the application waits behind it. Cancel, Escape and the window's close box all request cancellation. The window then shows "Canceling..." and stays open until the search stops at its next pair check, which took under 0.3 seconds on the real jobs measured. A canceled search moves no part, and the status bar reads "Expand Spacing canceled - no parts were moved". A search that finishes before the cancellation takes effect applies its result normally. While Auto Nest or a fill is still running on the nest, the command refuses with "Finish or cancel the current nesting or fill before Expand Spacing." because those operations can still add parts to the plate the search reads. The command does not save automatically.