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425 lines
16 KiB
C#
425 lines
16 KiB
C#
#nullable enable
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Threading;
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using System.Threading.Tasks;
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using Clipper2Lib;
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using OpenNest.Engine.Jobs;
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using OpenNest.Geometry;
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namespace OpenNest.Engine.NestingEngines.Irregular;
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/// <summary>Direction the packing front sweeps across the sheet (the free strip is left behind it).</summary>
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internal enum PackAxis
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{
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/// <summary>Front moves in +X; parts settle toward low X, then low Y.</summary>
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X,
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/// <summary>Front moves in +Y; parts settle toward low Y, then low X.</summary>
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Y,
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}
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internal sealed record Placed(Orientation Orientation, double X, double Y)
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{
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public double Left => X + Orientation.MinX;
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public double Right => X + Orientation.MaxX;
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public double Bottom => Y + Orientation.MinY;
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public double Top => Y + Orientation.MaxY;
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}
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internal sealed record SheetFill(NestPlateStock Stock, IReadOnlyList<Placed> Parts, double PartArea);
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/// <summary>
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/// Fills one sheet with a frontier-advance rule over incrementally maintained free regions.
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///
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/// For every (part type, orientation) still in play the packer keeps the exact set of legal
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/// reference points: the inner-fit rectangle of the work area minus the no-fit polygons of
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/// everything already placed. Each placement subtracts one translated NFP from each region,
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/// so regions only shrink, and a region that empties is retired for the rest of the sheet.
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///
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/// Choice rule, applied over all types and orientations at once (not in a fixed order):
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/// 1. Gap fill - if any part fits without pushing the packing front forward, place the
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/// largest such part at its lowest such point.
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/// 2. Otherwise advance - place the part whose front advance per unit area^beta is smallest,
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/// i.e. the one that buys the most material coverage for the sheet length it consumes.
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/// Parts are never placed in a sequence given up front; the sheet state decides what comes next.
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/// </summary>
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internal sealed class FrontierPacker
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{
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/// <summary>Slack added around the inner-fit rectangle so zero-width fits survive Clipper;
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/// chosen points are clamped back, which moves them far less than the clearance margin.</summary>
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private const double FitSlack = 2e-4;
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private const double Tie = 1e-6;
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private readonly IReadOnlyList<PartType> types;
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private readonly NoFitCache nfps;
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private readonly IReadOnlyDictionary<int, IReadOnlyList<PairPose>> pairs;
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private readonly NestPlateStock stock;
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private readonly PackAxis axis;
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private readonly double beta;
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private readonly Box work;
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private readonly WorkCounter counter;
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public FrontierPacker(
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IReadOnlyList<PartType> types,
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NoFitCache nfps,
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IReadOnlyDictionary<int, IReadOnlyList<PairPose>> pairs,
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NestPlateStock stock,
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PackAxis axis,
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double beta,
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WorkCounter counter
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)
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{
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this.counter = counter;
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this.types = types;
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this.nfps = nfps;
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this.pairs = pairs;
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this.stock = stock;
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this.axis = axis;
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this.beta = beta;
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work = stock.WorkArea;
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}
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public SheetFill Fill(IReadOnlyList<int> remaining, CancellationToken token)
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{
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var left = remaining.ToArray();
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var states = new List<Region>();
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var byOrientation = new Dictionary<Orientation, Region>(ReferenceEqualityComparer.Instance);
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bool Track(Orientation o, bool single)
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{
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if (byOrientation.ContainsKey(o))
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return true;
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if (!stock.Fits(o.Width, o.Height))
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return false;
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var region = new Region(o, work, single);
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states.Add(region);
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byOrientation[o] = region;
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return true;
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}
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var offered = new List<PairState>();
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foreach (var type in types)
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{
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if (left[type.Index] <= 0)
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continue;
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foreach (var o in type.Orientations)
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Track(o, single: true);
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if (left[type.Index] < 2 || !pairs.TryGetValue(type.Index, out var typePairs))
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continue;
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foreach (var pair in typePairs)
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{
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// Members missing from the catalog get regions too, but only for pair placement.
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if (stock.Fits(pair.Width, pair.Height) && Track(pair.A, single: false) && Track(pair.B, single: false))
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offered.Add(new PairState(pair, byOrientation[pair.A], byOrientation[pair.B]));
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}
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}
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var placed = new List<Placed>();
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var partArea = 0.0;
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var front = axis == PackAxis.X ? work.Left : work.Bottom;
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while (states.Count > 0)
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{
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token.ThrowIfCancellationRequested();
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var choice = Choose(states, offered, front);
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if (choice == null)
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break;
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var typeIndex = choice[0].Orientation.TypeIndex;
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foreach (var part in choice)
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{
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placed.Add(part);
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partArea += types[typeIndex].Area;
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front = System.Math.Max(front, axis == PackAxis.X ? part.Right : part.Top);
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}
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left[typeIndex] -= choice.Count;
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if (left[typeIndex] == 0)
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states.RemoveAll(s => s.Orientation.TypeIndex == typeIndex);
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if (left[typeIndex] < 2)
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{
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offered.RemoveAll(p => p.Pose.TypeIndex == typeIndex);
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states.RemoveAll(s => s.Orientation.TypeIndex == typeIndex && !s.Single);
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}
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// Each surviving region loses the positions the new parts now block. Regions are
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// independent, so they update in parallel without affecting determinism.
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var snapshot = states.ToArray();
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foreach (var part in choice)
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{
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counter.Add(snapshot.Length);
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Parallel.For(
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0,
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snapshot.Length,
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new ParallelOptions { CancellationToken = token },
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i => snapshot[i].Subtract(nfps.Get(part.Orientation, snapshot[i].Orientation), part.X, part.Y)
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);
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}
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states.RemoveAll(s => s.IsEmpty);
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offered.RemoveAll(p => p.A.IsEmpty || p.B.IsEmpty);
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if (offered.Count == 0)
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states.RemoveAll(s => !s.Single);
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}
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return new SheetFill(stock, placed, partArea);
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}
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/// <summary>
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/// The next placement: one part, or both members of a pair. Singles and pairs compete
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/// under the same rule; a pair counts as one piece of twice the part area, and on a tie
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/// the single (considered first) is kept.
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/// </summary>
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private IReadOnlyList<Placed>? Choose(List<Region> states, List<PairState> offered, double front)
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{
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IReadOnlyList<Placed>? bestParts = null;
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var bestFills = false;
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var bestValue = double.PositiveInfinity;
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var bestSide = double.PositiveInfinity;
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var bestLead = double.PositiveInfinity;
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var bestPriority = int.MaxValue;
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void Consider(Func<IReadOnlyList<Placed>> build, int typeIndex, double area, double advance, double side, double lead)
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{
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var priority = types[typeIndex].Part.Priority;
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if (priority > bestPriority)
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return;
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var fills = advance <= Tie;
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// Gap fill prefers bigger parts (negated area); advance prefers least advance per area.
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var value = fills ? -area : advance / System.Math.Pow(System.Math.Max(area, 1e-12), beta);
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var better = bestParts == null
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|| priority < bestPriority
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|| (fills && !bestFills)
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|| (
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fills == bestFills
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&& (
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value < bestValue - Tie * System.Math.Max(1, System.Math.Abs(bestValue))
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|| (
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value <= bestValue + Tie * System.Math.Max(1, System.Math.Abs(bestValue))
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&& (side < bestSide - Tie || (side <= bestSide + Tie && lead < bestLead - Tie))
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)
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)
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);
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if (!better)
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return;
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bestParts = build();
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bestPriority = priority;
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bestFills = fills;
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bestValue = value;
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bestSide = side;
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bestLead = lead;
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}
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foreach (var region in states)
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{
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if (!region.Single)
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continue;
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if (!region.TryLowest(axis, front, out var point, out var advance, out var side, out var lead))
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continue;
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var o = region.Orientation;
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Consider(() => new[] { new Placed(o, point.x, point.y) }, o.TypeIndex, types[o.TypeIndex].Area, advance, side, lead);
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}
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foreach (var state in offered)
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{
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var pair = state.Pose;
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if (!state.TryLowest(axis, front, counter, out var point, out var advance, out var side, out var lead))
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continue;
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Consider(
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() => new[] { new Placed(pair.A, point.x, point.y), new Placed(pair.B, point.x + pair.Dx, point.y + pair.Dy) },
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pair.TypeIndex,
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2 * types[pair.TypeIndex].Area,
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advance,
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side,
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lead
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);
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}
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return bestParts;
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}
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/// <summary>Legal reference points for one orientation on this sheet.</summary>
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private sealed class Region
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{
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private readonly double minX, minY, maxX, maxY;
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private PathsD free;
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private RectD bounds;
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public Region(Orientation orientation, Box work, bool single)
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{
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Orientation = orientation;
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Single = single;
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minX = work.Left - orientation.MinX;
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maxX = work.Right - orientation.MaxX;
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minY = work.Bottom - orientation.MinY;
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maxY = work.Top - orientation.MaxY;
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// Guard against fits that are infeasible by less than the bounds tolerance.
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if (maxX < minX)
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maxX = minX;
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if (maxY < minY)
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maxY = minY;
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free = new PathsD
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{
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new PathD
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{
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new(minX - FitSlack, minY - FitSlack),
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new(maxX + FitSlack, minY - FitSlack),
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new(maxX + FitSlack, maxY + FitSlack),
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new(minX - FitSlack, maxY + FitSlack),
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},
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};
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bounds = Clipper.GetBounds(free);
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}
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public Orientation Orientation { get; }
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/// <summary>False for a pair-only orientation: it is never placed on its own.</summary>
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public bool Single { get; }
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public bool IsEmpty => free.Count == 0;
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public void Subtract(Nfp nfp, double dx, double dy)
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{
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if (
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nfp.Bounds.right + dx < bounds.left
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|| nfp.Bounds.left + dx > bounds.right
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|| nfp.Bounds.bottom + dy < bounds.top
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|| nfp.Bounds.top + dy > bounds.bottom
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)
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return;
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var clip = Clipper.TranslatePaths(nfp.Region, dx, dy);
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free = Clipper.Difference(free, clip, FillRule.NonZero, NoFitCache.Precision);
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// Drop numerical dust; a sliver thinner than the precision grid is no real room.
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free.RemoveAll(p => p.Count < 3);
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bounds = free.Count == 0 ? default : Clipper.GetBounds(free);
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Version++;
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}
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/// <summary>Changes whenever the free region does.</summary>
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public int Version { get; private set; }
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public PathsD Free => free;
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public RectD Bounds => bounds;
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public double MinX => minX;
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public double MinY => minY;
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public double MaxX => maxX;
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public double MaxY => maxY;
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/// <summary>
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/// Best vertex of the free region: least front advance, then lowest cross-axis position,
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/// then lowest leading edge. Vertices suffice because every score is linear in position.
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/// </summary>
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public bool TryLowest(PackAxis axis, double front, out PointD point, out double advance, out double side, out double lead)
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{
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var o = Orientation;
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return BestVertex(free, minX, minY, maxX, maxY, (o.MinX, o.MinY, o.MaxX, o.MaxY),
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axis, front, out point, out advance, out side, out lead);
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}
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}
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/// <summary>
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/// Scores the vertices of <paramref name="free"/>, each clamped to the inner-fit box
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/// [minX, maxX] x [minY, maxY], for a piece occupying <paramref name="box"/> around its
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/// reference point.
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/// </summary>
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private static bool BestVertex(
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PathsD free,
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double minX,
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double minY,
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double maxX,
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double maxY,
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(double MinX, double MinY, double MaxX, double MaxY) box,
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PackAxis axis,
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double front,
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out PointD point,
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out double advance,
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out double side,
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out double lead
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)
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{
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point = default;
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advance = side = lead = double.PositiveInfinity;
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var found = false;
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foreach (var path in free)
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foreach (var raw in path)
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{
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var x = System.Math.Clamp(raw.x, minX, maxX);
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var y = System.Math.Clamp(raw.y, minY, maxY);
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double reach, across, start;
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if (axis == PackAxis.X)
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{
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reach = x + box.MaxX;
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across = y + box.MinY;
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start = x + box.MinX;
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}
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else
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{
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reach = y + box.MaxY;
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across = x + box.MinX;
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start = y + box.MinY;
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}
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var adv = System.Math.Max(0, reach - front);
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var better = !found
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|| adv < advance - Tie
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|| (adv <= advance + Tie && (across < side - Tie || (across <= side + Tie && start < lead - Tie)));
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if (!better)
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continue;
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found = true;
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point = new PointD(x, y);
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advance = adv;
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side = across;
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lead = start;
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}
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return found;
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}
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/// <summary>
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/// Legal reference points for a pair: member A's free region intersected with member B's
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/// moved back by the pair offset. Recomputed only after either member's region changes.
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/// </summary>
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private sealed class PairState(PairPose pose, Region a, Region b)
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{
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private int versionA = -1, versionB = -1;
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private PathsD free = new();
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public PairPose Pose { get; } = pose;
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public Region A { get; } = a;
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public Region B { get; } = b;
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public bool TryLowest(PackAxis axis, double front, WorkCounter counter,
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out PointD point, out double advance, out double side, out double lead)
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{
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if (versionA != A.Version || versionB != B.Version)
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{
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versionA = A.Version;
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versionB = B.Version;
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counter.Add(1);
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free = Intersect();
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}
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// Clamp into both members' inner-fit boxes; they overlap whenever the pair fits.
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var minX = System.Math.Max(A.MinX, B.MinX - Pose.Dx);
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var maxX = System.Math.Max(minX, System.Math.Min(A.MaxX, B.MaxX - Pose.Dx));
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var minY = System.Math.Max(A.MinY, B.MinY - Pose.Dy);
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var maxY = System.Math.Max(minY, System.Math.Min(A.MaxY, B.MaxY - Pose.Dy));
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return BestVertex(free, minX, minY, maxX, maxY, (Pose.MinX, Pose.MinY, Pose.MaxX, Pose.MaxY),
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axis, front, out point, out advance, out side, out lead);
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}
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private PathsD Intersect()
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{
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if (A.IsEmpty || B.IsEmpty)
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return new PathsD();
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var a = A.Bounds;
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var b = B.Bounds;
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if (b.right - Pose.Dx < a.left || b.left - Pose.Dx > a.right
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|| b.bottom - Pose.Dy < a.top || b.top - Pose.Dy > a.bottom)
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return new PathsD();
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var shifted = Clipper.TranslatePaths(B.Free, -Pose.Dx, -Pose.Dy);
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var result = Clipper.Intersect(A.Free, shifted, FillRule.NonZero, NoFitCache.Precision);
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result.RemoveAll(p => p.Count < 3);
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return result;
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}
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}
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}
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