/// <summary>
/// Constructs a new polygon.
/// </summary>
/// <remarks>A plane is created using first three vertices.</remarks>
/// <param name="vertices">A list of vertices that define the outline of the polygon.</param>
/// <param name="shared"> An identifier of shared properties.</param>
public Polygon(IList<Vertex> vertices, int shared)
{
if (vertices == null || vertices.Count < 3)
{
throw new ArgumentException("Not enough vertices.");
}
#if DEBUG
if (vertices.Count == 3) // No need to check triangles.
{
// Check if all vertices are on the same plane.
List<Vector3> edgeVectors = new List<Vector3>(vertices.Count);
for (int i = 1; i < vertices.Count; i++)
{
edgeVectors.Insert(i - 1, vertices[i].Position - vertices[i - 1].Position);
}
// Insert last edge.
edgeVectors.Add(vertices[0].Position - vertices[vertices.Count - 1].Position);
// Check if all edges are coplanar.
for (int i = 2; i < edgeVectors.Count; i++)
{
if (Vector3.Mixed(edgeVectors[i], edgeVectors[i - 1], edgeVectors[i - 2]) > MathHelpers.ZeroTolerance)
{
throw new ArgumentException("Vertices are not coplanar.");
}
}
}
#endif
this.Plane = new Plane(vertices[0].Position, vertices[1].Position, vertices[2].Position);
#if DEBUG
Plane.PlaneRelativePositionClass position = Plane.PlaneRelativePositionClass.Coplanar;
// Check if the polygon is convex.
for (int i = 0; i < vertices.Count; i++)
{
Vector3 previousVertex = vertices[(i == 0) ? vertices.Count - 1 : i - 1].Position;
Vector3 currentVertex = vertices[i].Position;
Vector3 nextVertex = vertices[(i + 1) % vertices.Count].Position;
// Plane formed by edge between previous vertex and current one and a vector
// that is parallel to polygon's normal and originates from current vertex.
ConstructiveSolidGeometry.Plane planeBefore =
new Plane(currentVertex, previousVertex, this.Plane.Normal + currentVertex);
position |= planeBefore.RelativePosition(nextVertex);
if (position == Plane.PlaneRelativePositionClass.Spanning)
{
throw new ArgumentException("Given list of vertices does not form a convex polygon.");
}
}
#endif
this.Vertices = vertices.ToList();
this.Shared = shared;
}
