private bool IsPointInTriangle(Point P, Point A, Point B, Point C)
{
float areaOfTriangle = Math.Abs(Matematics.Area(A, B, C));
float area_APB = Math.Abs(Matematics.Area(A, P, B));
float area_APC = Math.Abs(Matematics.Area(A, P, C));
float area_BPC = Math.Abs(Matematics.Area(B, P, C));
return(areaOfTriangle == area_APB + area_APC + area_BPC);
}
private void button_Triangulate_Click(object sender, EventArgs e)
{
double area = 0;
int count = Engine.points.Count;
if (count < 3)
{
return;
}
if (count == 3)
{
area = Matematics.Area(Engine.points[0], Engine.points[1], Engine.points[2]); return;
}
List <Point> points = Engine.points;// lista temporara
List <int> indexList = new List <int>();
for (int i = 0; i < points.Count; i++)
{
indexList.Add(i); //initializarea listei de indecsi de la 0 pana la nr de puncte
}
Point A;
Point B;
Point C;
while (indexList.Count > 3)
{
for (int i = 0; i < indexList.Count; i++)
{
int a = indexList[i]; // the index of current Item
int b = GetItem(indexList, i - 1); // the index of leftside neighbour
int c = GetItem(indexList, i + 1); // the index of righside neighbour
A = points[a];
B = points[b];
C = points[c];
int clockwise = GetTurnType(A, B, C);
if (clockwise != -1)
{
continue; // make a salt to next index
}
bool isEar = true; //presupunem ca este o ureche valida daca este
for (int j = 0; j < points.Count; j++)
{
if (j == a || j == b || j == c)
{
continue; //excluding the current index and the neighbours from test
}
if (IsPointInTriangle(points[j], A, B, C))
{
isEar = false;
break;
}
}
if (isEar)
{
Engine.triangles.Add(new Triangle(A, B, C)); //add the triangle in the list, if is a valid ear.
indexList.RemoveAt(i); //remove the current index from the indexlist
//drawing the line to make a triangle visualy
Pen pen = new Pen(Color.Green);
myGraphics.gfx.DrawLine(pen, C.X, C.Y, B.X, B.Y);
myGraphics.refreshGraph();
break;
}
}
}
//adding last 3 points what makes a triangle
A = points[indexList[0]];
B = points[indexList[1]];
C = points[indexList[2]];
Engine.triangles.Add(new Triangle(A, B, C));
// calculate the polygon area using triangle's area.
foreach (Triangle triangle in Engine.triangles)
{
area += Math.Abs(Matematics.Area(triangle.A, triangle.B, triangle.C));
}
points.Clear();
indexList.Clear();
output.Text = "Area:" + Environment.NewLine + area;
status = "triangulation completed";
}