setAsEdge method
Set this as a single edge.
Implementation
void setAsEdge(Vector2 v1, Vector2 v2) {
vertices.clear();
vertices.add(v1.clone());
vertices.add(v2.clone());
centroid
..setFrom(v1)
..add(v2)
..scale(0.5);
normals.clear();
normals.add(v2 - v1);
normals[0].scaleOrthogonalInto(-1.0, normals[0]);
normals[0].normalize();
normals.add(-normals[0]);
}