AJ Isaacs
1bc635acde
Includes fix for unlimited qty items (Quantity <= 0) that RemnantFiller.FillItems silently skips. Workaround: convert to estimated max capacity before passing in. Also removes caliper angle sections from spec — RotationAnalysis already feeds the caliper angle via FindBestRotation. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
89 lines
4.5 KiB
Markdown
89 lines
4.5 KiB
Markdown
# Iterative Shrink-Fill Design
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## Problem
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`StripNestEngine` currently picks a single "strip" drawing (the highest-area item), shrink-fills it into the tightest sub-region, then fills remnants with remaining drawings. This wastes potential density — every drawing benefits from shrink-filling into its tightest sub-region, not just the first one.
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## Design
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### 1. IterativeShrinkFiller
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New static class in `OpenNest.Engine/Fill/IterativeShrinkFiller.cs`.
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**Responsibility:** Given an ordered list of multi-quantity `NestItem` and a work area, iteratively shrink-fill each item into the tightest sub-region using `RemnantFiller` + `ShrinkFiller`, returning placed parts and leftovers.
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**Algorithm:**
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1. Create a `RemnantFiller` with the work area and spacing.
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2. Build a single fill function (closure) that wraps the caller-provided raw fill function with dual-direction shrink logic:
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- Calls `ShrinkFiller.Shrink` with `ShrinkAxis.Height` (bottom strip direction).
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- Calls `ShrinkFiller.Shrink` with `ShrinkAxis.Width` (left strip direction).
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- Compares results using `FillScore.Compute(parts, box)` where `box` is the remnant box passed by `RemnantFiller`. Since `FillScore` density is derived from placed parts' bounding box (not the work area parameter), the comparison is valid regardless of which box is used.
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- Returns the parts from whichever direction scores better.
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3. Pass this wrapper function and all items to `RemnantFiller.FillItems`, which drives the iteration — discovering free rectangles, iterating over items and boxes, and managing obstacle tracking.
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4. After `RemnantFiller.FillItems` returns, collect any unfilled quantities (including `Quantity <= 0` items which mean "unlimited") into a leftovers list.
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5. Return placed parts and leftovers. Remaining free space for the pack pass is reconstructed from placed parts by the caller (existing pattern), not by returning `RemnantFinder` state.
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**Data flow:** Caller provides a raw single-item fill function (e.g., `DefaultNestEngine.Fill`) → `IterativeShrinkFiller` wraps it in a dual-direction shrink closure → passes the wrapper to `RemnantFiller.FillItems` which drives the loop.
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**Note on quantities:** `Quantity <= 0` means "fill as many as possible" (unlimited). These items are included in the fill bucket (qty != 1), not the pack bucket.
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**Interface:**
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```csharp
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public class IterativeShrinkResult
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{
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public List<Part> Parts { get; set; }
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public List<NestItem> Leftovers { get; set; }
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}
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public static class IterativeShrinkFiller
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{
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public static IterativeShrinkResult Fill(
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List<NestItem> items,
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Box workArea,
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Func<NestItem, Box, List<Part>> fillFunc,
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double spacing,
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CancellationToken token);
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}
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```
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The class composes `RemnantFiller` and `ShrinkFiller` — it does not duplicate their logic.
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### 2. Revised StripNestEngine.Nest
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**Note:** The rotating calipers angle is already included via `RotationAnalysis.FindBestRotation`, which calls `RotatingCalipers.MinimumBoundingRectangle` and feeds the result as `bestRotation` into `AngleCandidateBuilder.Build`. No changes needed to the angle pipeline.
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The `Nest` override becomes a thin orchestrator:
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1. Separate items into multi-quantity (qty != 1) and singles (qty == 1).
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2. Sort multi-quantity items by `Priority` ascending, then `Drawing.Area` descending.
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3. Call `IterativeShrinkFiller.Fill` with the sorted multi-quantity items.
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4. Collect leftovers: unfilled multi-quantity remainders + all singles.
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5. If leftovers exist and free space remains, run `PackArea` into the remaining area.
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6. Deduct placed quantities from the original items. Return all parts.
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**Deleted code:**
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- `SelectStripItemIndex` method
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- `EstimateStripDimension` method
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- `TryOrientation` method
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- `ShrinkFill` method
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**Deleted files:**
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- `StripNestResult.cs`
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- `StripDirection.cs`
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## Files Changed
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| File | Change |
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|------|--------|
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| `OpenNest.Engine/Fill/IterativeShrinkFiller.cs` | New — orchestrates RemnantFiller + ShrinkFiller with dual-direction selection |
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| `OpenNest.Engine/StripNestEngine.cs` | Rewrite Nest to use IterativeShrinkFiller + pack leftovers |
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| `OpenNest.Engine/StripNestResult.cs` | Delete |
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| `OpenNest.Engine/StripDirection.cs` | Delete |
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## Not In Scope
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- Trying multiple item orderings and picking the best overall `FillScore` — future follow-up once we confirm the iterative approach is fast enough.
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- Changes to `NestEngineBase`, `DefaultNestEngine`, `RemnantFiller`, `ShrinkFiller`, `RemnantFinder`, `AngleCandidateBuilder`, `NestItem`, or UI code.
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