feat: add OpenNest.Gpu project with PartBitmap rasterizer

Introduces the OpenNest.Gpu class library with ILGPU dependencies and a
PartBitmap class that rasterizes Drawing closed shapes into integer grids
for GPU-based overlap testing. Supports rotation and spacing dilation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest.Gpu/OpenNest.Gpu.csproj

@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0-windows</TargetFramework>
+    <RootNamespace>OpenNest.Gpu</RootNamespace>
+    <AssemblyName>OpenNest.Gpu</AssemblyName>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\OpenNest.Core\OpenNest.Core.csproj" />
+    <ProjectReference Include="..\OpenNest.Engine\OpenNest.Engine.csproj" />
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="ILGPU" Version="1.5.1" />
+    <PackageReference Include="ILGPU.Algorithms" Version="1.5.1" />
+  </ItemGroup>
+</Project>

OpenNest.Gpu/PartBitmap.cs

@@ -0,0 +1,155 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using OpenNest.Converters;
+using OpenNest.Geometry;
+using OpenNest.Math;
+
+namespace OpenNest.Gpu
+{
+    public class PartBitmap
+    {
+        public int[] Cells { get; set; }
+        public int Width { get; set; }
+        public int Height { get; set; }
+        public double CellSize { get; set; }
+        public double OriginX { get; set; }
+        public double OriginY { get; set; }
+
+        public const double DefaultCellSize = 0.05;
+
+        public static PartBitmap FromDrawing(Drawing drawing, double cellSize = DefaultCellSize, double spacingDilation = 0)
+        {
+            var polygons = GetClosedPolygons(drawing);
+            return Rasterize(polygons, cellSize, spacingDilation);
+        }
+
+        public static PartBitmap FromDrawingRotated(Drawing drawing, double rotation, double cellSize = DefaultCellSize, double spacingDilation = 0)
+        {
+            var polygons = GetClosedPolygons(drawing);
+
+            if (!rotation.IsEqualTo(0))
+            {
+                foreach (var poly in polygons)
+                    poly.Rotate(rotation);
+            }
+
+            return Rasterize(polygons, cellSize, spacingDilation);
+        }
+
+        private static PartBitmap Rasterize(List<Polygon> polygons, double cellSize, double spacingDilation)
+        {
+            if (polygons.Count == 0)
+                return new PartBitmap { Cells = Array.Empty<int>(), Width = 0, Height = 0, CellSize = cellSize };
+
+            var minX = double.MaxValue;
+            var minY = double.MaxValue;
+            var maxX = double.MinValue;
+            var maxY = double.MinValue;
+
+            foreach (var poly in polygons)
+            {
+                poly.UpdateBounds();
+                var bb = poly.BoundingBox;
+                if (bb.Left < minX) minX = bb.Left;
+                if (bb.Bottom < minY) minY = bb.Bottom;
+                if (bb.Right > maxX) maxX = bb.Right;
+                if (bb.Top > maxY) maxY = bb.Top;
+            }
+
+            minX -= spacingDilation;
+            minY -= spacingDilation;
+            maxX += spacingDilation;
+            maxY += spacingDilation;
+
+            var width = (int)System.Math.Ceiling((maxX - minX) / cellSize);
+            var height = (int)System.Math.Ceiling((maxY - minY) / cellSize);
+
+            if (width <= 0 || height <= 0)
+                return new PartBitmap { Cells = Array.Empty<int>(), Width = 0, Height = 0, CellSize = cellSize };
+
+            var cells = new int[width * height];
+
+            for (var y = 0; y < height; y++)
+            {
+                for (var x = 0; x < width; x++)
+                {
+                    var px = minX + (x + 0.5) * cellSize;
+                    var py = minY + (y + 0.5) * cellSize;
+                    var pt = new Vector(px, py);
+
+                    foreach (var poly in polygons)
+                    {
+                        if (poly.ContainsPoint(pt))
+                        {
+                            cells[y * width + x] = 1;
+                            break;
+                        }
+                    }
+                }
+            }
+
+            var dilationCells = (int)System.Math.Ceiling(spacingDilation / cellSize);
+
+            if (dilationCells > 0)
+                Dilate(cells, width, height, dilationCells);
+
+            return new PartBitmap
+            {
+                Cells = cells,
+                Width = width,
+                Height = height,
+                CellSize = cellSize,
+                OriginX = minX,
+                OriginY = minY
+            };
+        }
+
+        private static List<Polygon> GetClosedPolygons(Drawing drawing)
+        {
+            var entities = ConvertProgram.ToGeometry(drawing.Program)
+                .Where(e => e.Layer != SpecialLayers.Rapid);
+            var shapes = Helper.GetShapes(entities);
+
+            var polygons = new List<Polygon>();
+
+            foreach (var shape in shapes)
+            {
+                if (!shape.IsClosed())
+                    continue;
+
+                var polygon = shape.ToPolygonWithTolerance(0.05);
+                polygon.Close();
+                polygons.Add(polygon);
+            }
+
+            return polygons;
+        }
+
+        private static void Dilate(int[] cells, int width, int height, int radius)
+        {
+            var source = (int[])cells.Clone();
+
+            for (var y = 0; y < height; y++)
+            {
+                for (var x = 0; x < width; x++)
+                {
+                    if (source[y * width + x] != 1)
+                        continue;
+
+                    for (var dy = -radius; dy <= radius; dy++)
+                    {
+                        for (var dx = -radius; dx <= radius; dx++)
+                        {
+                            var nx = x + dx;
+                            var ny = y + dy;
+
+                            if (nx >= 0 && nx < width && ny >= 0 && ny < height)
+                                cells[ny * width + nx] = 1;
+                        }
+                    }
+                }
+            }
+        }
+    }
+}

OpenNest.sln

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 EndProject
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 EndProject
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