OpenNest/OpenNest.Engine/BestFit/PolygonHelper.cs

using OpenNest.Converters;
using OpenNest.Geometry;
using OpenNest.Math;
using System.Linq;

namespace OpenNest.Engine.BestFit
{
    public static class PolygonHelper
    {
        public static PolygonExtractionResult ExtractPerimeterPolygon(Drawing drawing, double halfSpacing)
        {
            var entities = ConvertProgram.ToGeometry(drawing.Program)
                .Where(e => e.Layer != SpecialLayers.Rapid)
                .ToList();

            if (entities.Count == 0)
                return new PolygonExtractionResult(null, Vector.Zero);

            var definedShape = new ShapeProfile(entities);
            var perimeter = definedShape.Perimeter;

            if (perimeter == null)
                return new PolygonExtractionResult(null, Vector.Zero);

            // Inflate by half-spacing if spacing is non-zero.
            // Detect winding direction to choose the correct outward offset side.
            var outwardSide = OffsetSide.Right;
            if (halfSpacing > 0)
            {
                var testPoly = perimeter.ToPolygon();
                if (testPoly.Vertices.Count >= 3 && testPoly.RotationDirection() == RotationType.CW)
                    outwardSide = OffsetSide.Left;
            }

            var inflated = halfSpacing > 0
                ? (perimeter.OffsetEntity(halfSpacing, outwardSide) as Shape ?? perimeter)
                : perimeter;

            // Convert to polygon with circumscribed arcs for tight nesting.
            var polygon = inflated.ToPolygonWithTolerance(0.01, circumscribe: true);

            if (polygon.Vertices.Count < 3)
                return new PolygonExtractionResult(null, Vector.Zero);

            // Normalize: move polygon to origin.
            polygon.UpdateBounds();
            var bb = polygon.BoundingBox;
            polygon.Offset(-bb.Left, -bb.Bottom);

            // No correction needed: BestFitFinder always pairs the same drawing with
            // itself, so the polygon-to-part offset is identical for both parts and
            // cancels out in the NFP displacement.
            return new PolygonExtractionResult(polygon, Vector.Zero);
        }

        public static Polygon RotatePolygon(Polygon polygon, double angle, bool reNormalize = true)
        {
            if (angle.IsEqualTo(0))
                return polygon;

            var result = new Polygon();
            var cos = System.Math.Cos(angle);
            var sin = System.Math.Sin(angle);

            foreach (var v in polygon.Vertices)
            {
                result.Vertices.Add(new Vector(
                    v.X * cos - v.Y * sin,
                    v.X * sin + v.Y * cos));
            }

            if (reNormalize)
            {
                // Re-normalize to origin.
                result.UpdateBounds();
                var bb = result.BoundingBox;
                result.Offset(-bb.Left, -bb.Bottom);
            }

            return result;
        }
    }

    public record PolygonExtractionResult(Polygon Polygon, Vector Correction);
}