void CL_EarClipTriangulator_Impl::create_lists(bool create_ear_list)
{
int vert_size = vertices.size();
for( int i=0; i < vert_size; ++i )
{
LinkedVertice *v = vertices[i];
if( i == 0 )
v->previous = vertices.back();
else
v->previous = vertices[i-1];
if( i == (vert_size-1) )
v->next = vertices.front();
else
v->next = vertices[i+1];
}
unsigned int hole_size = hole.size();
for( unsigned int j = 0; j < hole.size(); ++j )
{
if( j == 0 )
hole[j]->previous = hole.back();
else
hole[j]->previous = hole[j-1];
if( j == (hole_size-1) )
hole[j]->next = hole.front();
else
hole[j]->next = hole[j+1];
}
if( create_ear_list )
{
// cl_write_console_line("Ear list:");
for( std::vector<LinkedVertice*>::iterator it = vertices.begin(); it != vertices.end(); ++it )
{
if( is_ear(*(*it)) )
{
ear_list.push_back((*it));
(*it)->is_ear = true;
// cl_write_console_line(cl_format(" (%1,%2)", (*it)->x, (*it)->y ) );
}
}
}
}
CL_EarClipResult CL_EarClipTriangulator_Impl::triangulate()
{
create_lists(true);
int num_triangles = vertices.size()-2;
int tri_count = 0;
CL_EarClipResult result(num_triangles);
while( tri_count < num_triangles )
{
if( ear_list.empty() ) // something went wrong, but lets not crash anyway.
break;
LinkedVertice *v = ear_list.back();
ear_list.pop_back();
CL_EarClipTriangulator_Triangle tri;
tri.x1 = v->x;
tri.y1 = v->y;
tri.x2 = v->previous->x;
tri.y2 = v->previous->y;
tri.x3 = v->next->x;
tri.y3 = v->next->y;
result.get_triangles().push_back(tri);
v->next->previous = v->previous;
v->previous->next = v->next;
if( is_ear(*v->next) )
{
if( v->next->is_ear == false ) // not marked as an ear yet. Mark it, and add to the list.
{
v->next->is_ear = true;
ear_list.push_back(v->next);
}
}
else
{
if( v->next->is_ear == true ) // Not an ear any more. Delete from ear list.
{
v->next->is_ear = false;
std::vector<LinkedVertice*>::iterator it;
for( it = ear_list.begin(); it != ear_list.end(); ++it )
{
if( (*it) == v->next )
{
ear_list.erase(it);
break;
}
}
}
}
if( is_ear(*v->previous) )
{
if( v->previous->is_ear == false ) // not marked as an ear yet. Mark it, and add to the list.
{
v->previous->is_ear = true;
ear_list.push_back(v->previous);
}
}
else
{
if( v->previous->is_ear == true ) // Not an ear any more. Delete from ear list.
{
v->previous->is_ear = false;
std::vector<LinkedVertice*>::iterator it;
for( it = ear_list.begin(); it != ear_list.end(); ++it )
{
if( (*it) == v->previous )
{
ear_list.erase(it);
break;
}
}
}
}
/* cl_write_console_line("Ear list:");
for( std::vector<LinkedVertice*>::iterator it = ear_list.begin(); it != ear_list.end(); ++it )
{
cl_write_console_line(" (%1,%2)", (*it)->x, (*it)->y );
}
cl_write_console_line("");
*/
tri_count++;
}
// cl_write_console_line("num triangles - final: %1", tri_count );
return result;
}
vector<Triangle> Math::triangulate(const vector<Vertex> &polygon)
{
if (polygon.size() < 3)
throw love::Exception("Not a polygon");
else if (polygon.size() == 3)
return vector<Triangle>(1, Triangle(polygon[0], polygon[1], polygon[2]));
// collect list of connections and record leftmost item to check if the polygon
// has the expected winding
vector<size_t> next_idx(polygon.size()), prev_idx(polygon.size());
size_t idx_lm = 0;
for (size_t i = 0; i < polygon.size(); ++i)
{
const Vertex &lm = polygon[idx_lm], &p = polygon[i];
if (p.x < lm.x || (p.x == lm.x && p.y < lm.y))
idx_lm = i;
next_idx[i] = i+1;
prev_idx[i] = i-1;
}
next_idx[next_idx.size()-1] = 0;
prev_idx[0] = prev_idx.size()-1;
// check if the polygon has the expected winding and reverse polygon if needed
if (!is_oriented_ccw(polygon[prev_idx[idx_lm]], polygon[idx_lm], polygon[next_idx[idx_lm]]))
next_idx.swap(prev_idx);
// collect list of concave polygons
list<const Vertex *> concave_vertices;
for (size_t i = 0; i < polygon.size(); ++i)
{
if (!is_oriented_ccw(polygon[prev_idx[i]], polygon[i], polygon[next_idx[i]]))
concave_vertices.push_back(&polygon[i]);
}
// triangulation according to kong
vector<Triangle> triangles;
size_t n_vertices = polygon.size();
size_t current = 1, skipped = 0, next, prev;
while (n_vertices > 3)
{
next = next_idx[current];
prev = prev_idx[current];
const Vertex &a = polygon[prev], &b = polygon[current], &c = polygon[next];
if (is_ear(a,b,c, concave_vertices))
{
triangles.push_back(Triangle(a,b,c));
next_idx[prev] = next;
prev_idx[next] = prev;
concave_vertices.remove(&b);
--n_vertices;
skipped = 0;
}
else if (++skipped > n_vertices)
{
throw love::Exception("Cannot triangulate polygon.");
}
current = next;
}
next = next_idx[current];
prev = prev_idx[current];
triangles.push_back(Triangle(polygon[prev], polygon[current], polygon[next]));
return triangles;
}