True-Shape Nesting
A nesting method that places parts according to their exact geometric outline — including curves, holes, and irregular edges — rather than fitting each part into a rectangular bounding box.
What is true-shape nesting?
True-shape nesting (also called irregular nesting or arbitrary-shape nesting) is a method of placing parts onto a sheet material so that each part occupies only the space its actual geometry requires — not a rectangular box around it.
Rectangular nesting vs. true-shape nesting
In rectangular nesting, each part is enclosed in its bounding box (the smallest rectangle that fits around the part), and those boxes are arranged on the sheet. This is fast to compute but wastes significant material when parts have irregular outlines, concave curves, or cutouts.
In true-shape nesting, the actual part geometry is used. Two L-shaped parts, for example, can be rotated and interlocked so they fit together almost like puzzle pieces — dramatically increasing sheet utilization.
Why it matters
| Scenario | Rectangular nesting | True-shape nesting |
|---|---|---|
| 20 identical L-shapes on a 2500×1250mm sheet | ~52% utilization | ~89% utilization |
| 50 mixed irregular parts | ~60% utilization | ~82% utilization |
| Simple rectangular parts | ~88% utilization | ~91% utilization |
The difference is most pronounced for curved, L-shaped, T-shaped, or complex parts — common in sheet metal fabrication, laser cutting, and composites.
How true-shape nesting works
True-shape nesting algorithms use computational geometry techniques — most commonly the No-Fit Polygon (NFP) method — to determine all valid positions where one part can be placed relative to another without overlap. The optimizer then searches through possible arrangements to find the one that minimizes wasted area.
Modern metaheuristic approaches (genetic algorithms, simulated annealing) explore a large number of possible placements to find near-optimal solutions within reasonable time.
True-shape nesting in Lapas
Lapas performs true-shape nesting by default. It supports all standard DXF geometry types — LWPOLYLINE, ARC, CIRCLE, SPLINE, and ELLIPSE — and handles concave and convex polygons, parts with internal holes, and nested INSERT/BLOCK entities.
The optimizer offers two engines:
- Heuristic engine — fast (seconds), good quality for most jobs
- Metaheuristic engine — deeper search, higher utilization, takes longer for complex jobs
Both engines perform true-shape, not rectangular, placement.
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