private Boolean is_ear(Point p) // checks if given vertice is in a ear
{
mPolygon m = new mPolygon(updated_vertices); // init. a polygon from the current vertices
if (m.is_vertex(p) == true) // if given point is a vertex
{
if (m.vertex_type(p) == VertexType.ConvexPoint) // and it's a convex point
{
Point curr_point = p;
Point prev_point = m.get_prev_point(p); // find previous adjacent point
Point next_point = m.get_next_point(p); // find next adjacent point
for (int i = updated_vertices.GetLowerBound(0); i < updated_vertices.GetUpperBound(0); i++) // loop through all other vertices
{
Point pt = updated_vertices[i];
if (!(is_points_equal(pt, curr_point) || is_points_equal(pt, prev_point) || is_points_equal(pt, next_point)))
{ // if pt is not equal to checked vertice or its's next and prev adjacent vertices
if (is_point_in_triangle(new Point[] { prev_point, curr_point, next_point }, pt)) // check pt lies in triangle
{
return(false); // if another vertice lies in this triangle, then this is not an ear
}
}
}
}
else // concave
{
return(false); // we cannot make ears from concave points
}
return(true); // if CS:IP reaches here, this means vertice passed the test and is an ear
}
return(false); // if the given vertex is not an vertex, it's not related to an ear also!
}
private void update_vertices(Point p) // called after finding a ear from a vertice
{ // removes the vertice from updates_vertices list
ArrayList temp_points = new ArrayList(); // temp. location while updating the list
for (int i = 0; i < updated_vertices.Length; i++) // loop through the list
{
if (p == updated_vertices[i]) // if we found the vertice we'r lookig for
{
mPolygon poly = new mPolygon(updated_vertices);
Point curr_point = p;
Point next_point = poly.get_next_point(p); // find the vertices next neighboor
Point prev_point = poly.get_prev_point(p); // find the vertices previous neighboor
Point[] ear = new Point[3]; // create a 3 point triangle-polygon from these 3 points
ear[0] = prev_point; // previos vertice
ear[1] = curr_point; // current vertice
ear[2] = next_point; // next vertice
ears.Add(ear); // add this ear to ears list
}
else // this is not the vertice we'r looking for
{
temp_points.Add(updated_vertices[i]); // so add it to temp. vertice list
}
}
if ((updated_vertices.Length - temp_points.Count) == 1) // we removed 1 vertice from the list, check the counts
{
updated_vertices = new Point[updated_vertices.Length - 1]; // redimension the list to -1 size, cause we removed 1 vertice
for (int i = 0; i < temp_points.Count; i++)
{
updated_vertices[i] = (Point)temp_points[i]; // update the newest updated_vertices from temp location
}
}
}
public void triangulate() // triangulate the bigger polygon-shape
{
mPolygon poly = new mPolygon(updated_vertices); // create a polygon from the current vertices
Boolean finished = false; // triangulation-finished?
if (updated_vertices.Length == 3) // if there's only 3 points, no need to run algorithm
{
finished = true;
}
Point p = new Point();
while (finished == false) // loop while triangulation not finished yet
{
int i = 0;
Boolean not_found = true; // did we found an ear? no, not yet
while (not_found && (i < updated_vertices.Length)) // while we did not found any ear and not yet processed all vertices
{
p = updated_vertices[i]; // get current point
if (is_ear(p)) // check if we can get an ear from that vertice
{
not_found = false; // good we found one
}
else
{
i++; // continue to search
}
}
update_vertices(p); // remove the vertice we found the ear from the updated_vertices list
poly = new mPolygon(updated_vertices); // reupdate the polygon from the rest of vertices
if (updated_vertices.Length == 3) // if there's only 3 vertice left
{
finished = true; // this means we finished the triangulation
}
}
// when the CS:IP reaches here, this means triangulation finished
polygons = new Point[ears.Count + 1][]; // init polygons structure to ears.count + 1(for last 3 points left)
for (int i = 0; i < ears.Count; i++)
{
Point[] points = (Point[])ears[i]; // move ears to final triangulated polygons list
polygons[i] = new Point[3];
polygons[i][0] = points[0];
polygons[i][1] = points[1];
polygons[i][2] = points[2];
}
// we have 3 left vertices on updated_vertices list, - the last triangulated polygon -
polygons[ears.Count] = new Point[updated_vertices.Length]; // add it to triangulated polygons list also
for (int i = 0; i < updated_vertices.Length; i++)
{
polygons[ears.Count][i] = updated_vertices[i];
}
}
