/**********************************************************
* 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(Coordinate[] trianglePts, Coordinate pt)
{
if (trianglePts.Length != 3)
{
return(false);
}
for (int i = trianglePts.GetLowerBound(0);
i < trianglePts.GetUpperBound(0); i++)
{
if (pt.Equals(trianglePts[i]))
{
return(true);
}
}
bool bIn = false;
LineSegmentEquation line0 = new LineSegmentEquation(
trianglePts[0], trianglePts[1]);
LineSegmentEquation line1 = new LineSegmentEquation(
trianglePts[1], trianglePts[2]);
LineSegmentEquation line2 = new LineSegmentEquation(
trianglePts[2], trianglePts[0]);
if (line0.OnLine(pt) || line1.OnLine(pt) || line2.OnLine(pt))
{
bIn = true;
}
else //point is not in the lines
{
double dblArea0 = PolygonHelper.PolygonArea(
new Coordinate[] { trianglePts[0], trianglePts[1], pt });
double dblArea1 = PolygonHelper.PolygonArea(
new Coordinate[] { trianglePts[1], trianglePts[2], pt });
double dblArea2 = PolygonHelper.PolygonArea(
new Coordinate[] { 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 fill m_aUpdatedPolygonVertices array with input array.
*
* m_aUpdatedPolygonVertices is a working array that will
* be updated when an ear is cut till m_aUpdatedPolygonVertices
* makes triangle (a convex polygon).
******************************************************/
private void SetUpdatedPolygonVertices()
{
int nVertices = m_aInputVertices.Length;
m_aUpdatedPolygonVertices = new Coordinate[nVertices];
for (int i = 0; i < nVertices; i++)
{
m_aUpdatedPolygonVertices[i] = m_aInputVertices[i];
}
//m_aUpdatedPolygonVertices should be in count clock wise
if (PolygonHelper.PointsDirection(m_aUpdatedPolygonVertices)
== PolygonDirection.Clockwise)
{
PolygonHelper.ReversePointsDirection(m_aUpdatedPolygonVertices);
}
}
/****************************************************************
* 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(Coordinate vertex)
{
PolygonHelper polygon = new PolygonHelper(m_aUpdatedPolygonVertices);
if (polygon.PolygonVertex(vertex))
{
bool bEar = true;
if (polygon.VertexType(vertex) == PolygonVertexType.ConvexPoint)
{
Coordinate pi = vertex;
Coordinate pj = polygon.PreviousPoint(vertex); //previous vertex
Coordinate pk = polygon.NextPoint(vertex); //next vertex
for (int i = m_aUpdatedPolygonVertices.GetLowerBound(0);
i < m_aUpdatedPolygonVertices.GetUpperBound(0); i++)
{
Coordinate pt = m_aUpdatedPolygonVertices[i];
if (!(pt.Equals(pi) || pt.Equals(pj) || pt.Equals(pk)))
{
if (TriangleContainsPoint(new Coordinate[] { 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;
{
Debug.WriteLine("IsEarOfUpdatedPolygon: " +
"Not a polygon vertex");
return(false);
}
}
/********************************************************
* To update m_aUpdatedPolygonVertices:
* Take out Vertex from m_aUpdatedPolygonVertices array, add 3 points
* to the m_aEars
**********************************************************/
private void UpdatePolygonVertices(Coordinate vertex)
{
ArrayList alTempPts = new ArrayList();
for (int i = 0; i < m_aUpdatedPolygonVertices.Length; i++)
{
//add 3 pts to FEars
if (vertex.Equals(m_aUpdatedPolygonVertices[i]))
{
PolygonHelper polygon = new PolygonHelper(m_aUpdatedPolygonVertices);
Coordinate pti = vertex;
Coordinate ptj = polygon.PreviousPoint(vertex); //previous point
Coordinate ptk = polygon.NextPoint(vertex); //next point
//3 vertices of each ear
Coordinate[] aEar = new Coordinate[3];
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 Coordinate[nLength - 1];
for (int i = 0; i < alTempPts.Count; i++)
{
m_aUpdatedPolygonVertices[i] = (Coordinate)alTempPts[i];
}
}
}
