/*******************************************************
To cut an ear from polygon to make ears and an updated polygon:
*******************************************************/
public void CutEar()
{
CPolygon polygon=new CPolygon(m_aUpdatedPolygonVertices);
bool bFinish=false;
//if (polygon.GetPolygonType()==PolygonType.Convex) //don't have to cut ear
// bFinish=true;
if (m_aUpdatedPolygonVertices.Length==3) //triangle, don't have to cut ear
bFinish=true;
CPoint2D pt=new CPoint2D();
while (bFinish==false) //UpdatedPolygon
{
int i=0;
bool bNotFound=true;
while (bNotFound
&& (i<m_aUpdatedPolygonVertices.Length)) //loop till find an ear
{
pt=m_aUpdatedPolygonVertices[i];
if (IsEarOfUpdatedPolygon(pt))
bNotFound=false; //got one, pt is an ear
else
i++;
} //bNotFount
//An ear found:}
if (pt !=null)
UpdatePolygonVertices(pt);
polygon=new CPolygon(m_aUpdatedPolygonVertices);
//if ((polygon.GetPolygonType()==PolygonType.Convex)
// && (m_aUpdatedPolygonVertices.Length==3))
if (m_aUpdatedPolygonVertices.Length==3)
bFinish=true;
} //bFinish=false
SetPolygons();
}
/********************************************************
To update m_aUpdatedPolygonVertices:
Take out Vertex from m_aUpdatedPolygonVertices array, add 3 points
to the m_aEars
**********************************************************/
private void UpdatePolygonVertices(CPoint2D 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);
CPoint2D pti = vertex;
CPoint2D ptj = polygon.PreviousPoint(vertex); //previous point
CPoint2D ptk = polygon.NextPoint(vertex); //next point
CPoint2D[] aEar=new CPoint2D[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 CPoint2D[nLength-1];
for (int i=0; i<alTempPts.Count; i++)
m_aUpdatedPolygonVertices[i]=(CPoint2D)alTempPts[i];
}
}
/****************************************************************
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(CPoint2D vertex )
{
CPolygon polygon=new CPolygon(m_aUpdatedPolygonVertices);
if (polygon.PolygonVertex(vertex))
{
bool bEar=true;
if (polygon.PolygonVertexType(vertex)==VertexType.ConvexPoint)
{
CPoint2D pi=vertex;
CPoint2D pj=polygon.PreviousPoint(vertex); //previous vertex
CPoint2D pk=polygon.NextPoint(vertex);//next vertex
for (int i=m_aUpdatedPolygonVertices.GetLowerBound(0);
i<m_aUpdatedPolygonVertices.GetUpperBound(0); i++)
{
CPoint2D pt = m_aUpdatedPolygonVertices[i];
if ( !(pt.EqualsPoint(pi)|| pt.EqualsPoint(pj)||pt.EqualsPoint(pk)))
{
if (TriangleContainsPoint(new CPoint2D[] {pj, pi, pk}, 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;
}
}
