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#ifndef __MANIFOLD_H

#define __MANIFOLD_H

#include <vector>

#include <list>

#include <map>

#include "Vertex.h"

#include "HalfEdge.h"

#include "Face.h"

namespace HMesh

{

	class VertexCirculator;

	class FaceCirculator;

	/** \brief A Data structure representing an open or closed manifold.

			Manifold keeps lists of the entities making up a halfedge mesh

			and provides basic functions for creating new faces, halfedges

			and vertices. There are also primitive operations for editing 

			such as edge collapse. */

	struct Manifold

	{

		std::list<Vertex> vertex_db;

		std::list<Face> face_db;

		std::list<HalfEdge> halfedge_db;

		/** Remove a face if it contains only two edges.

				This is an auxiliary function called from collapse_halfedge. */

		void remove_face_if_degenerate(HalfEdgeIter fi);

		/** Empty copy constructor.

				Copying a manifold will not work, since faces, vertices, and

				halfedges contain iterators pointing to other faces, vertices,

				and halfedges. These pointers would need to be changed if the 

				mesh were copied. In other words, we would need to walk the

				entire mesh. This may be required but it should not be an 

				operation that is easily invoked by calling the copy constructor.

				Hence, this operator is made private.		*/

		Manifold(const Manifold& m2) {}

		/** Empty assignment operator.

				The assignment operator is private for the same reason that the

				copy constructor is private. */

		const Manifold& operator=(const Manifold& m2) {}

		public:

		/// Construct an empty manifold.

		Manifold() {}

		/// Return the bounding box of the manifold.

		void get_bbox(CGLA::Vec3f&, CGLA::Vec3f&);

		/// Get a bounding sphere

    void get_bsphere(CGLA::Vec3f& c, float& r);

		/// Clear the manifold - removing all data.

		void clear()

		{

			vertex_db.clear();

			face_db.clear();

			halfedge_db.clear();

		}

		/// Return the number of faces.

		int no_faces() const {return face_db.size();}

		/// Return the number of halfedges.

		int no_halfedges() const {return halfedge_db.size();}

		/// Return the number of vertices

		int no_vertices() const {return vertex_db.size();}

		/// Create a new vertex at a given position.

		VertexIter create_vertex(const CGLA::Vec3f& pos)

		{

			vertex_db.push_back(Vertex(pos));

			return --vertex_db.end();

		}

		/// Create a new face 

		FaceIter create_face()

		{

			face_db.push_back(Face());

			return --face_db.end();

		}

		/// Create a new halfedge.

		HalfEdgeIter create_halfedge()

		{

			halfedge_db.push_back(HalfEdge());

			return --halfedge_db.end();

		}

		/// Erase halfedge. Assumes it is safe to do so. Use with care.

		void erase_halfedge(HalfEdgeIter he)

		{

			halfedge_db.erase(he);

		}

		/// Erase vertex. Assumes it is safe to do so. Use with care.

		void erase_vertex(VertexIter v)

		{

			vertex_db.erase(v);

		}

		/// Erase face. Assumes it is safe to do so. Use with care.

		void erase_face(FaceIter f)

		{

			face_db.erase(f);

		}

		/// Return iterator pointing to the first halfedge.

		HalfEdgeIter halfedges_begin() { return halfedge_db.begin();}

		/// Return iterator pointing to beyond the last halfedge.

		HalfEdgeIter halfedges_end() { return halfedge_db.end(); }

		/// Return iterator pointing to the first vertex.

		VertexIter vertices_begin() { return vertex_db.begin();}

		/// Return iterator pointing to beyond the last vertex.

		VertexIter vertices_end() { return vertex_db.end(); }

		/// Return iterator pointing to the first face.

		FaceIter faces_begin() { return face_db.begin();	}

		/// Return iterator pointing to beyond the last face.

		FaceIter faces_end() { return face_db.end(); }

		/** \brief HalfEdge collapse precondition. 

				If this function does not return true, it is illegal to collapse

				the halfedge given as second arg. The reason is that the collapse

				would violate the manifold property of the mesh.

				The test is as follows.

				1. For the two vertices adjacent to the edge, we generate

				a list of all their neighbouring vertices. We then generate a 

				list of the vertices that occur in both these lists. That is, 

				we find all vertices connected by edges to both endpoints

				of the edge and store these in a list.

				2. For both faces incident on the edge, check whether they

				are triangular. If this is the case, the face will be removed,

				and it is ok that the the third vertex is connected to both 

				endpoints. Thus the third vertex in such a face is removed

				from the list generated in 1.

				3. If the list is now empty, all is well. Otherwise, there

				would be a vertex in the new mesh with two edges connecting

				it to the same vertex. Return false.

				4. TETRAHEDRON TEST:

				If the valency of both vertices is 

				three, and the incident faces are triangles, we also disallow

				the operation. Reason: It introduces a vertex of valency two

				and if the final two polygons incident on the vertices 

				that are adjacent to the edge being collapsed are triangles, then

				the construction will collapse

				5. VALENCY 4 TEST:

				If a face adjacent to the edge being collapsed is a triangle,

				it will disappear, and the valency of the final vertex beloning to

				this edge will be reduced by one. Hence this valency should be at

				least 4. A valency three vertex will be reduced to a valency two

				vertex which is considered illegal.

				6. PREVENT MERGING HOLES:

				We do not want to collapse an edge if its end points are boundary

				vertices, but its two adjacent faces are not NULL faces, because

				in that case we create a vertex where two holes meet. A non manifold

				situation.	*/

		bool collapse_precond(VertexIter, HalfEdgeIter);

		/** Collapse the halfedge given as second argument. 

				The first argument is the vertex that is being removed. The

				second is a halfedge pointing away from that vertex.

				The final argument is a boolean indicating whether the vertex

				that survives the collapse should have a position which is the

				average of its own position and the vertex that is removed.

				By default false.

				This function is not guaranteed to keep the mesh sane unless,

				collapse_precond has returned true.

		*/

		void collapse_halfedge(VertexIter, HalfEdgeIter, bool=false);

		/** Split a face.

		    The face given as first argument is split by connecting two

				vertices (the next two arguments). */

		FaceIter split_face(FaceIter, VertexIter, VertexIter);

		/** Insert a new vertex on the halfedge given as argument.

				The new halfedge is insterted as the previous edge to the one

				given as argument.

		*/

		VertexIter Manifold::split_edge(HalfEdgeIter h);

		/** Triangulate a polygonal face by repeatedly calling split_face. 

				Triangulate iteratively splits triangles off a polygon. The first 

				triangle split off is the one connecting f->last->vert and

				f->last->next->next->vert.

		*/

		void triangulate(FaceIter);

		/** Triangulate a polygon by inserting a vertex at the barycenter and 

				connecting all vertices to this vertex. 

				The word "safe" means that it is less likely to create flipped

				triangles than the normal triangulate. On the other hand, it 

				introduces more vertices and probably makes the triangles more

				acute.

				This function simply calls face_insert_point.

		*/

		VertexIter safe_triangulate(FaceIter f);

		/** Insert a new vertex (second arg.) in a face (first arg.).

				This operation splits an N-gon into N triangles.

				In the current implementation the original face is erased. 

				This means that the iterator is not valid after the function

				returns. 

		*/

		void face_insert_point(FaceIter f, VertexIter);

		/** Merges two faces into a single polygon. The first face is the first

				argument. The second face is adjacent to the first along the

				halfedge given as second argument. */

		bool merge_faces(FaceIter f, HalfEdgeIter h);

		/** Flip an edge. Returns false if flipping cannot be performed.

				This is either because one of the two adjacent faces is not

				a triangle, or because either end point has valency three or

				because the vertices that will be connected already are. */

		bool flip(HalfEdgeIter);

		/** Performs a series of tests to check that this is a valid manifold.

				This function is not rigorously constructed but seems to catch

				all problems so far. */

		bool is_valid();

		/** Give each vertex a unique id corresponding to its iterator 

				position */

		void enumerate_vertices();

		/** Give each halfedge a unique id corresponding to its iterator 

				position */

		void enumerate_halfedges();

		/** Give each face a unique id corresponding to its iterator 

				position */

		void enumerate_faces();

	};

}

#endif