/****************************************************************
* 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];
}
}
}