/**************************************************************** * To check whether the Vertex is an ear or not based updated Polygon vertices * * ref. www-cgrl.cs.mcgill.ca/~godfried/teaching/cg-projects/97/Ian * /algorithm1.html * * If it is an ear, return true, * If it is not an ear, return false; *****************************************************************/ private bool IsEarOfUpdatedPolygon(MyVector2 vertex) { CPolygon polygon = new CPolygon(m_aUpdatedPolygonVertices); if (polygon.PolygonVertex(vertex)) { bool bEar = true; if (polygon.PolygonVertexType(vertex) == VertexType.ConvexPoint) { MyVector2 pi = vertex; MyVector2 pj = polygon.PreviousPoint(vertex); //previous vertex MyVector2 pk = polygon.NextPoint(vertex); //next vertex for (int i = m_aUpdatedPolygonVertices.GetLowerBound(0); i < m_aUpdatedPolygonVertices.GetUpperBound(0); i++) { MyVector2 pt = m_aUpdatedPolygonVertices[i]; if (!(pt.EqualsPoint(pi) || pt.EqualsPoint(pj) || pt.EqualsPoint(pk))) { MyVector2[] vecs = new MyVector2[3] { pj, pi, pk }; if (TriangleContainsPoint(vecs, pt)) { bEar = false; } } } } //ThePolygon.getVertexType(Vertex)=ConvexPt else //concave point { bEar = false; //not an ear/ } return(bEar); } else //not a polygon vertex; { System.Diagnostics.Trace.WriteLine("IsEarOfUpdatedPolygon: " + "Not a polygon vertex"); return(false); } }
/********************************************************** * To check the Pt is in the Triangle or not. * If the Pt is in the line or is a vertex, then return true. * If the Pt is out of the Triangle, then return false. * * This method is used for triangle only. ***********************************************************/ private bool TriangleContainsPoint(MyVector2[] trianglePts, MyVector2 pt) { if (trianglePts.Length != 3) { return(false); } for (int i = trianglePts.GetLowerBound(0); i < trianglePts.GetUpperBound(0); i++) { if (pt.EqualsPoint(trianglePts[i])) { return(true); } } bool bIn = false; CLineSegment line0 = new CLineSegment(trianglePts[0], trianglePts[1]); CLineSegment line1 = new CLineSegment(trianglePts[1], trianglePts[2]); CLineSegment line2 = new CLineSegment(trianglePts[2], trianglePts[0]); if (line0.PointInLine(pt) || line1.PointInLine(pt) || line2.PointInLine(pt)) { bIn = true; } else //point is not in the lines { double dblArea0 = CPolygon.PolygonArea(new MyVector2[] { trianglePts[0], trianglePts[1], pt }); double dblArea1 = CPolygon.PolygonArea(new MyVector2[] { trianglePts[1], trianglePts[2], pt }); double dblArea2 = CPolygon.PolygonArea(new MyVector2[] { trianglePts[2], trianglePts[0], pt }); if (dblArea0 > 0) { if ((dblArea1 > 0) && (dblArea2 > 0)) { bIn = true; } } else if (dblArea0 < 0) { if ((dblArea1 < 0) && (dblArea2 < 0)) { bIn = true; } } } return(bIn); }
/******************************************************** * To update m_aUpdatedPolygonVertices: * Take out Vertex from m_aUpdatedPolygonVertices array, add 3 points * to the m_aEars **********************************************************/ private void UpdatePolygonVertices(MyVector2 vertex) { System.Collections.ArrayList alTempPts = new System.Collections.ArrayList(); for (int i = 0; i < m_aUpdatedPolygonVertices.Length; i++) { if (vertex.EqualsPoint( m_aUpdatedPolygonVertices[i])) //add 3 pts to FEars { CPolygon polygon = new CPolygon(m_aUpdatedPolygonVertices); MyVector2 pti = vertex; MyVector2 ptj = polygon.PreviousPoint(vertex); //previous point MyVector2 ptk = polygon.NextPoint(vertex); //next point MyVector2[] aEar = new MyVector2[3]; //3 vertices of each ear aEar[0] = ptj; aEar[1] = pti; aEar[2] = ptk; m_alEars.Add(aEar); } else { alTempPts.Add(m_aUpdatedPolygonVertices[i]); } //not equal points } if (m_aUpdatedPolygonVertices.Length - alTempPts.Count == 1) { int nLength = m_aUpdatedPolygonVertices.Length; m_aUpdatedPolygonVertices = new MyVector2[nLength - 1]; for (int i = 0; i < alTempPts.Count; i++) { m_aUpdatedPolygonVertices[i] = (MyVector2)alTempPts[i]; } } }