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IABSD.fr/xenocara/lib/libGLU/src/libtess/mesh.h
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/* * SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008) * Copyright (C) 1991-2000 Silicon Graphics, Inc. All Rights Reserved. * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice including the dates of first publication and * either this permission notice or a reference to * http://oss.sgi.com/projects/FreeB/ * shall be included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * SILICON GRAPHICS, INC. BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF * OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. * * Except as contained in this notice, the name of Silicon Graphics, Inc. * shall not be used in advertising or otherwise to promote the sale, use or * other dealings in this Software without prior written authorization from * Silicon Graphics, Inc. */ /* ** Author: Eric Veach, July 1994. ** */ #ifndef __mesh_h_ #define __mesh_h_ #include <GL/glu.h> typedef struct GLUmesh GLUmesh; typedef struct GLUvertex GLUvertex; typedef struct GLUface GLUface; typedef struct GLUhalfEdge GLUhalfEdge; typedef struct ActiveRegion ActiveRegion; /* Internal data */ /* The mesh structure is similar in spirit, notation, and operations * to the "quad-edge" structure (see L. Guibas and J. Stolfi, Primitives * for the manipulation of general subdivisions and the computation of * Voronoi diagrams, ACM Transactions on Graphics, 4(2):74-123, April 1985). * For a simplified description, see the course notes for CS348a, * "Mathematical Foundations of Computer Graphics", available at the * Stanford bookstore (and taught during the fall quarter). * The implementation also borrows a tiny subset of the graph-based approach * use in Mantyla's Geometric Work Bench (see M. Mantyla, An Introduction * to Sold Modeling, Computer Science Press, Rockville, Maryland, 1988). * * The fundamental data structure is the "half-edge". Two half-edges * go together to make an edge, but they point in opposite directions. * Each half-edge has a pointer to its mate (the "symmetric" half-edge Sym), * its origin vertex (Org), the face on its left side (Lface), and the * adjacent half-edges in the CCW direction around the origin vertex * (Onext) and around the left face (Lnext). There is also a "next" * pointer for the global edge list (see below). * * The notation used for mesh navigation: * Sym = the mate of a half-edge (same edge, but opposite direction) * Onext = edge CCW around origin vertex (keep same origin) * Dnext = edge CCW around destination vertex (keep same dest) * Lnext = edge CCW around left face (dest becomes new origin) * Rnext = edge CCW around right face (origin becomes new dest) * * "prev" means to substitute CW for CCW in the definitions above. * * The mesh keeps global lists of all vertices, faces, and edges, * stored as doubly-linked circular lists with a dummy header node. * The mesh stores pointers to these dummy headers (vHead, fHead, eHead). * * The circular edge list is special; since half-edges always occur * in pairs (e and e->Sym), each half-edge stores a pointer in only * one direction. Starting at eHead and following the e->next pointers * will visit each *edge* once (ie. e or e->Sym, but not both). * e->Sym stores a pointer in the opposite direction, thus it is * always true that e->Sym->next->Sym->next == e. * * Each vertex has a pointer to next and previous vertices in the * circular list, and a pointer to a half-edge with this vertex as * the origin (NULL if this is the dummy header). There is also a * field "data" for client data. * * Each face has a pointer to the next and previous faces in the * circular list, and a pointer to a half-edge with this face as * the left face (NULL if this is the dummy header). There is also * a field "data" for client data. * * Note that what we call a "face" is really a loop; faces may consist * of more than one loop (ie. not simply connected), but there is no * record of this in the data structure. The mesh may consist of * several disconnected regions, so it may not be possible to visit * the entire mesh by starting at a half-edge and traversing the edge * structure. * * The mesh does NOT support isolated vertices; a vertex is deleted along * with its last edge. Similarly when two faces are merged, one of the * faces is deleted (see __gl_meshDelete below). For mesh operations, * all face (loop) and vertex pointers must not be NULL. However, once * mesh manipulation is finished, __gl_MeshZapFace can be used to delete * faces of the mesh, one at a time. All external faces can be "zapped" * before the mesh is returned to the client; then a NULL face indicates * a region which is not part of the output polygon. */ struct GLUvertex { GLUvertex *next; /* next vertex (never NULL) */ GLUvertex *prev; /* previous vertex (never NULL) */ GLUhalfEdge *anEdge; /* a half-edge with this origin */ void *data; /* client's data */ /* Internal data (keep hidden) */ GLdouble coords[3]; /* vertex location in 3D */ GLdouble s, t; /* projection onto the sweep plane */ long pqHandle; /* to allow deletion from priority queue */ }; struct GLUface { GLUface *next; /* next face (never NULL) */ GLUface *prev; /* previous face (never NULL) */ GLUhalfEdge *anEdge; /* a half edge with this left face */ void *data; /* room for client's data */ /* Internal data (keep hidden) */ GLUface *trail; /* "stack" for conversion to strips */ GLboolean marked; /* flag for conversion to strips */ GLboolean inside; /* this face is in the polygon interior */ }; struct GLUhalfEdge { GLUhalfEdge *next; /* doubly-linked list (prev==Sym->next) */ GLUhalfEdge *Sym; /* same edge, opposite direction */ GLUhalfEdge *Onext; /* next edge CCW around origin */ GLUhalfEdge *Lnext; /* next edge CCW around left face */ GLUvertex *Org; /* origin vertex (Overtex too long) */ GLUface *Lface; /* left face */ /* Internal data (keep hidden) */ ActiveRegion *activeRegion; /* a region with this upper edge (sweep.c) */ int winding; /* change in winding number when crossing from the right face to the left face */ }; #define Rface Sym->Lface #define Dst Sym->Org #define Oprev Sym->Lnext #define Lprev Onext->Sym #define Dprev Lnext->Sym #define Rprev Sym->Onext #define Dnext Rprev->Sym /* 3 pointers */ #define Rnext Oprev->Sym /* 3 pointers */ struct GLUmesh { GLUvertex vHead; /* dummy header for vertex list */ GLUface fHead; /* dummy header for face list */ GLUhalfEdge eHead; /* dummy header for edge list */ GLUhalfEdge eHeadSym; /* and its symmetric counterpart */ }; /* The mesh operations below have three motivations: completeness, * convenience, and efficiency. The basic mesh operations are MakeEdge, * Splice, and Delete. All the other edge operations can be implemented * in terms of these. The other operations are provided for convenience * and/or efficiency. * * When a face is split or a vertex is added, they are inserted into the * global list *before* the existing vertex or face (ie. e->Org or e->Lface). * This makes it easier to process all vertices or faces in the global lists * without worrying about processing the same data twice. As a convenience, * when a face is split, the "inside" flag is copied from the old face. * Other internal data (v->data, v->activeRegion, f->data, f->marked, * f->trail, e->winding) is set to zero. * * ********************** Basic Edge Operations ************************** * * __gl_meshMakeEdge( mesh ) creates one edge, two vertices, and a loop. * The loop (face) consists of the two new half-edges. * * __gl_meshSplice( eOrg, eDst ) is the basic operation for changing the * mesh connectivity and topology. It changes the mesh so that * eOrg->Onext <- OLD( eDst->Onext ) * eDst->Onext <- OLD( eOrg->Onext ) * where OLD(...) means the value before the meshSplice operation. * * This can have two effects on the vertex structure: * - if eOrg->Org != eDst->Org, the two vertices are merged together * - if eOrg->Org == eDst->Org, the origin is split into two vertices * In both cases, eDst->Org is changed and eOrg->Org is untouched. * * Similarly (and independently) for the face structure, * - if eOrg->Lface == eDst->Lface, one loop is split into two * - if eOrg->Lface != eDst->Lface, two distinct loops are joined into one * In both cases, eDst->Lface is changed and eOrg->Lface is unaffected. * * __gl_meshDelete( eDel ) removes the edge eDel. There are several cases: * if (eDel->Lface != eDel->Rface), we join two loops into one; the loop * eDel->Lface is deleted. Otherwise, we are splitting one loop into two; * the newly created loop will contain eDel->Dst. If the deletion of eDel * would create isolated vertices, those are deleted as well. * * ********************** Other Edge Operations ************************** * * __gl_meshAddEdgeVertex( eOrg ) creates a new edge eNew such that * eNew == eOrg->Lnext, and eNew->Dst is a newly created vertex. * eOrg and eNew will have the same left face. * * __gl_meshSplitEdge( eOrg ) splits eOrg into two edges eOrg and eNew, * such that eNew == eOrg->Lnext. The new vertex is eOrg->Dst == eNew->Org. * eOrg and eNew will have the same left face. * * __gl_meshConnect( eOrg, eDst ) creates a new edge from eOrg->Dst * to eDst->Org, and returns the corresponding half-edge eNew. * If eOrg->Lface == eDst->Lface, this splits one loop into two, * and the newly created loop is eNew->Lface. Otherwise, two disjoint * loops are merged into one, and the loop eDst->Lface is destroyed. * * ************************ Other Operations ***************************** * * __gl_meshNewMesh() creates a new mesh with no edges, no vertices, * and no loops (what we usually call a "face"). * * __gl_meshUnion( mesh1, mesh2 ) forms the union of all structures in * both meshes, and returns the new mesh (the old meshes are destroyed). * * __gl_meshDeleteMesh( mesh ) will free all storage for any valid mesh. * * __gl_meshZapFace( fZap ) destroys a face and removes it from the * global face list. All edges of fZap will have a NULL pointer as their * left face. Any edges which also have a NULL pointer as their right face * are deleted entirely (along with any isolated vertices this produces). * An entire mesh can be deleted by zapping its faces, one at a time, * in any order. Zapped faces cannot be used in further mesh operations! * * __gl_meshCheckMesh( mesh ) checks a mesh for self-consistency. */ GLUhalfEdge *__gl_meshMakeEdge( GLUmesh *mesh ); int __gl_meshSplice( GLUhalfEdge *eOrg, GLUhalfEdge *eDst ); int __gl_meshDelete( GLUhalfEdge *eDel ); GLUhalfEdge *__gl_meshAddEdgeVertex( GLUhalfEdge *eOrg ); GLUhalfEdge *__gl_meshSplitEdge( GLUhalfEdge *eOrg ); GLUhalfEdge *__gl_meshConnect( GLUhalfEdge *eOrg, GLUhalfEdge *eDst ); GLUmesh *__gl_meshNewMesh( void ); GLUmesh *__gl_meshUnion( GLUmesh *mesh1, GLUmesh *mesh2 ); void __gl_meshDeleteMesh( GLUmesh *mesh ); void __gl_meshZapFace( GLUface *fZap ); #ifdef NDEBUG #define __gl_meshCheckMesh( mesh ) #else void __gl_meshCheckMesh( GLUmesh *mesh ); #endif #endif