private void GenerateTerrain(int gx, int gy) { FP ax = gx * CellSize; FP ay = gy * CellSize; List <Vertices> polys = MarchingSquares.DetectSquares(new AABB(new FPVector2(ax, ay), new FPVector2(ax + CellSize, ay + CellSize)), SubCellSize, SubCellSize, _terrainMap, Iterations, true); if (polys.Count == 0) { return; } _bodyMap[gx, gy] = new List <Body>(); // create the scale vector FPVector2 scale = new FPVector2(1f / PointsPerUnit, 1f / -PointsPerUnit); // create physics object for this grid cell foreach (Vertices item in polys) { // does this need to be negative? item.Scale(ref scale); item.Translate(ref _topLeft); Vertices simplified = SimplifyTools.CollinearSimplify(item, FP.Zero); List <Vertices> decompPolys = Triangulate.ConvexPartition(simplified, Decomposer, true, FP.EN3); foreach (Vertices poly in decompPolys) { if (poly.Count > 2) { _bodyMap[gx, gy].Add(BodyFactory.CreatePolygon(World, poly, 1, null)); } } } }
/// <summary> /// Implements "A new algorithm for Boolean operations on general polygons" /// available here: http://liama.ia.ac.cn/wiki/_media/user:dong:dong_cg_05.pdf /// Merges two polygons, a subject and a clip with the specified operation. Polygons may not be /// self-intersecting. /// /// Warning: May yield incorrect results or even crash if polygons contain collinear points. /// </summary> /// <param name="subject">The subject polygon.</param> /// <param name="clip">The clip polygon, which is added, /// substracted or intersected with the subject</param> /// <param name="clipType">The operation to be performed. Either /// Union, Difference or Intersection.</param> /// <param name="error">The error generated (if any)</param> /// <returns>A list of closed polygons, which make up the result of the clipping operation. /// Outer contours are ordered counter clockwise, holes are ordered clockwise.</returns> private static List <Vertices> Execute(Vertices subject, Vertices clip, PolyClipType clipType, out PolyClipError error) { Debug.Assert(subject.IsSimple() && clip.IsSimple(), "Non simple input!", "Input polygons must be simple (cannot intersect themselves)."); // Copy polygons Vertices slicedSubject; Vertices slicedClip; // Calculate the intersection and touch points between // subject and clip and add them to both CalculateIntersections(subject, clip, out slicedSubject, out slicedClip); // Translate polygons into upper right quadrant // as the algorithm depends on it FPVector2 lbSubject = subject.GetAABB().LowerBound; FPVector2 lbClip = clip.GetAABB().LowerBound; FPVector2 translate; FPVector2.Min(ref lbSubject, ref lbClip, out translate); translate = FPVector2.one - translate; if (translate != FPVector2.zero) { slicedSubject.Translate(ref translate); slicedClip.Translate(ref translate); } // Enforce counterclockwise contours slicedSubject.ForceCounterClockWise(); slicedClip.ForceCounterClockWise(); List <Edge> subjectSimplices; List <FP> subjectCoeff; List <Edge> clipSimplices; List <FP> clipCoeff; // Build simplical chains from the polygons and calculate the // the corresponding coefficients CalculateSimplicalChain(slicedSubject, out subjectCoeff, out subjectSimplices); CalculateSimplicalChain(slicedClip, out clipCoeff, out clipSimplices); List <Edge> resultSimplices; // Determine the characteristics function for all non-original edges // in subject and clip simplical chain and combine the edges contributing // to the result, depending on the clipType CalculateResultChain(subjectCoeff, subjectSimplices, clipCoeff, clipSimplices, clipType, out resultSimplices); List <Vertices> result; // Convert result chain back to polygon(s) error = BuildPolygonsFromChain(resultSimplices, out result); // Reverse the polygon translation from the beginning // and remove collinear points from output translate *= -1f; for (int i = 0; i < result.Count; ++i) { result[i].Translate(ref translate); SimplifyTools.CollinearSimplify(result[i], FP.Zero); } return(result); }