/*---------------------------------------------------------------------
* Prints out n-3 diagonals (as pairs of integer indices)
* which form a triangulation of P. This algorithm is O(n^2).
* See Chapter 1 for a full explanation.
* Triangulate operates on listcopy rather than list, so that
* the original polygon is not destroyed.
*/
public void Triangulate()
{
cVertex v0, v1, v2, v3, v4; // five consecutive vertices
cDiagonal diag;
int n = listcopy.n; //number of vertices; shrinks to 3
bool earfound = false; //to prevent infinite loop on improper input
EarInit();
/* Each step of outer loop removes one ear. */
while (n > 3)
{
/* Inner loop searches for an ear. */
v2 = listcopy.head;
do
{
if (v2.IsEar)
{
/* Ear found. Fill variables. */
v3 = v2.NextVertex; v4 = v3.NextVertex;
v1 = v2.PrevVertex; v0 = v1.PrevVertex;
/* (v1,v3) is a diagonal */
earfound = true;
diag = new cDiagonal(v1, v3);
diag.PrintDiagonal(listcopy.n - n);
diaglist.InsertBeforeHead(diag);
/* Update earity of diagonal endpoints */
v1.IsEar = Diagonal(v0, v3);
v3.IsEar = Diagonal(v1, v4);
/* Cut off the ear v2 */
v1.NextVertex = v3;
v3.PrevVertex = v1;
listcopy.head = v3; /* In case the head was v2. */
n--;
break; /* out of inner loop; resume outer loop */
} /* end if ear found */
v2 = v2.NextVertex;
} while (v2 != listcopy.head);
if (!earfound)
{
System.Diagnostics.Debug.WriteLine("Polygon is nonsimple: cannot triangulate");
break;
}
else
{
earfound = false;
}
diagdrawn = false;
} /* end outer while loop */
}
public void PrintDiagonals()
{
cDiagonal temp = head;
int i = 0;
do
{
temp.PrintDiagonal(i);
temp = temp.next;
i++;
} while (temp != head);
}
