OpenNest/docs/plans/2026-03-08-remnant-fill-investigation.md

Remnant Fill Optimization — Try More Rotations

Problem

NestEngine.Fill(NestItem, Box) gets 7 parts in a narrow remnant strip where manual nesting gets 9 — all at the same rotation. The engine simply isn't trying the rotation angle that fits best.

Test Case

Load C:/Users/AJ/Desktop/N0308-008.zip — 75 parts on a 36x36 plate. Remnant strip is at (31.0, 0.8) 4.7x35.0.

load_nest("C:/Users/AJ/Desktop/N0308-008.zip")
fill_remnants(0, "Converto 3 YRD DUMPERSTER HINGE PLATE #2")  → gets 7, should get 9

Root Cause

In NestEngine.Fill(NestItem, Box) (OpenNest.Engine/NestEngine.cs:32-105), the rotation candidates are:

1. bestRotation from RotationAnalysis.FindBestRotation(item)
2. bestRotation + 90°
3. If the strip is narrow relative to the part, a sweep every 5° from 0° to 175°

The narrow-strip sweep triggers when workAreaShortSide < partLongestSide. For this strip (4.7" wide, part is 5.89x3.39), the short side is 4.7 and the part's longest side is 5.89, so the sweep should trigger. But the winning rotation may still not be found because:

• The sweep only runs on the bestRotation-normalized part dimensions
• FillLinear may not be optimal for all angles — check if FillRectangleBestFit and FillWithPairs are also tried at each sweep angle

Fix

Ensure all three fill strategies (FillLinear, FillRectangleBestFit, FillWithPairs) are tried across the full set of rotation candidates, not just FillLinear.

Files

• OpenNest.Engine/NestEngine.cs:32-105 — Fill(NestItem, Box) rotation logic
• OpenNest.Engine/BestFit/RotationAnalysis.cs — FindBestRotation
• OpenNest.Engine/FillLinear.cs — linear tiling