dll/opengl/mesa/src/glu/sgi/libtess/mesh.h

   1 /*
   2  * SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008)
   3  * Copyright (C) 1991-2000 Silicon Graphics, Inc. All Rights Reserved.
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  10  * Software is furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice including the dates of first publication and
  13  * either this permission notice or a reference to
  14  * http://oss.sgi.com/projects/FreeB/
  15  * shall be included in all copies or substantial portions of the Software.
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  30 /*
  31 ** Author: Eric Veach, July 1994.
  32 **
  33 */
  34
  35 #ifndef __mesh_h_
  36 #define __mesh_h_
  37
  38 #include <GL/glu.h>
  39
  40 typedef struct GLUmesh GLUmesh;
  41
  42 typedef struct GLUvertex GLUvertex;
  43 typedef struct GLUface GLUface;
  44 typedef struct GLUhalfEdge GLUhalfEdge;
  45
  46 typedef struct ActiveRegion ActiveRegion;       /* Internal data */
  47
  48 /* The mesh structure is similar in spirit, notation, and operations
  49  * to the "quad-edge" structure (see L. Guibas and J. Stolfi, Primitives
  50  * for the manipulation of general subdivisions and the computation of
  51  * Voronoi diagrams, ACM Transactions on Graphics, 4(2):74-123, April 1985).
  52  * For a simplified description, see the course notes for CS348a,
  53  * "Mathematical Foundations of Computer Graphics", available at the
  54  * Stanford bookstore (and taught during the fall quarter).
  55  * The implementation also borrows a tiny subset of the graph-based approach
  56  * use in Mantyla's Geometric Work Bench (see M. Mantyla, An Introduction
  57  * to Sold Modeling, Computer Science Press, Rockville, Maryland, 1988).
  58  *
  59  * The fundamental data structure is the "half-edge".  Two half-edges
  60  * go together to make an edge, but they point in opposite directions.
  61  * Each half-edge has a pointer to its mate (the "symmetric" half-edge Sym),
  62  * its origin vertex (Org), the face on its left side (Lface), and the
  63  * adjacent half-edges in the CCW direction around the origin vertex
  64  * (Onext) and around the left face (Lnext).  There is also a "next"
  65  * pointer for the global edge list (see below).
  66  *
  67  * The notation used for mesh navigation:
  68  *      Sym   = the mate of a half-edge (same edge, but opposite direction)
  69  *      Onext = edge CCW around origin vertex (keep same origin)
  70  *      Dnext = edge CCW around destination vertex (keep same dest)
  71  *      Lnext = edge CCW around left face (dest becomes new origin)
  72  *      Rnext = edge CCW around right face (origin becomes new dest)
  73  *
  74  * "prev" means to substitute CW for CCW in the definitions above.
  75  *
  76  * The mesh keeps global lists of all vertices, faces, and edges,
  77  * stored as doubly-linked circular lists with a dummy header node.
  78  * The mesh stores pointers to these dummy headers (vHead, fHead, eHead).
  79  *
  80  * The circular edge list is special; since half-edges always occur
  81  * in pairs (e and e->Sym), each half-edge stores a pointer in only
  82  * one direction.  Starting at eHead and following the e->next pointers
  83  * will visit each *edge* once (ie. e or e->Sym, but not both).
  84  * e->Sym stores a pointer in the opposite direction, thus it is
  85  * always true that e->Sym->next->Sym->next == e.
  86  *
  87  * Each vertex has a pointer to next and previous vertices in the
  88  * circular list, and a pointer to a half-edge with this vertex as
  89  * the origin (NULL if this is the dummy header).  There is also a
  90  * field "data" for client data.
  91  *
  92  * Each face has a pointer to the next and previous faces in the
  93  * circular list, and a pointer to a half-edge with this face as
  94  * the left face (NULL if this is the dummy header).  There is also
  95  * a field "data" for client data.
  96  *
  97  * Note that what we call a "face" is really a loop; faces may consist
  98  * of more than one loop (ie. not simply connected), but there is no
  99  * record of this in the data structure.  The mesh may consist of
 100  * several disconnected regions, so it may not be possible to visit
 101  * the entire mesh by starting at a half-edge and traversing the edge
 102  * structure.
 103  *
 104  * The mesh does NOT support isolated vertices; a vertex is deleted along
 105  * with its last edge.  Similarly when two faces are merged, one of the
 106  * faces is deleted (see __gl_meshDelete below).  For mesh operations,
 107  * all face (loop) and vertex pointers must not be NULL.  However, once
 108  * mesh manipulation is finished, __gl_MeshZapFace can be used to delete
 109  * faces of the mesh, one at a time.  All external faces can be "zapped"
 110  * before the mesh is returned to the client; then a NULL face indicates
 111  * a region which is not part of the output polygon.
 112  */
 113
 114 struct GLUvertex {
 115   GLUvertex     *next;          /* next vertex (never NULL) */
 116   GLUvertex     *prev;          /* previous vertex (never NULL) */
 117   GLUhalfEdge   *anEdge;        /* a half-edge with this origin */
 118   void          *data;          /* client's data */
 119
 120   /* Internal data (keep hidden) */
 121   GLdouble      coords[3];      /* vertex location in 3D */
 122   GLdouble      s, t;           /* projection onto the sweep plane */
 123   long          pqHandle;       /* to allow deletion from priority queue */
 124 };
 125
 126 struct GLUface {
 127   GLUface       *next;          /* next face (never NULL) */
 128   GLUface       *prev;          /* previous face (never NULL) */
 129   GLUhalfEdge   *anEdge;        /* a half edge with this left face */
 130   void          *data;          /* room for client's data */
 131
 132   /* Internal data (keep hidden) */
 133   GLUface       *trail;         /* "stack" for conversion to strips */
 134   GLboolean     marked;         /* flag for conversion to strips */
 135   GLboolean     inside;         /* this face is in the polygon interior */
 136 };
 137
 138 struct GLUhalfEdge {
 139   GLUhalfEdge   *next;          /* doubly-linked list (prev==Sym->next) */
 140   GLUhalfEdge   *Sym;           /* same edge, opposite direction */
 141   GLUhalfEdge   *Onext;         /* next edge CCW around origin */
 142   GLUhalfEdge   *Lnext;         /* next edge CCW around left face */
 143   GLUvertex     *Org;           /* origin vertex (Overtex too long) */
 144   GLUface       *Lface;         /* left face */
 145
 146   /* Internal data (keep hidden) */
 147   ActiveRegion  *activeRegion;  /* a region with this upper edge (sweep.c) */
 148   int           winding;        /* change in winding number when crossing
 149                                    from the right face to the left face */
 150 };
 151
 152 #define Rface   Sym->Lface
 153 #define Dst     Sym->Org
 154
 155 #define Oprev   Sym->Lnext
 156 #define Lprev   Onext->Sym
 157 #define Dprev   Lnext->Sym
 158 #define Rprev   Sym->Onext
 159 #define Dnext   Rprev->Sym      /* 3 pointers */
 160 #define Rnext   Oprev->Sym      /* 3 pointers */
 161
 162
 163 struct GLUmesh {
 164   GLUvertex     vHead;          /* dummy header for vertex list */
 165   GLUface       fHead;          /* dummy header for face list */
 166   GLUhalfEdge   eHead;          /* dummy header for edge list */
 167   GLUhalfEdge   eHeadSym;       /* and its symmetric counterpart */
 168 };
 169
 170 /* The mesh operations below have three motivations: completeness,
 171  * convenience, and efficiency.  The basic mesh operations are MakeEdge,
 172  * Splice, and Delete.  All the other edge operations can be implemented
 173  * in terms of these.  The other operations are provided for convenience
 174  * and/or efficiency.
 175  *
 176  * When a face is split or a vertex is added, they are inserted into the
 177  * global list *before* the existing vertex or face (ie. e->Org or e->Lface).
 178  * This makes it easier to process all vertices or faces in the global lists
 179  * without worrying about processing the same data twice.  As a convenience,
 180  * when a face is split, the "inside" flag is copied from the old face.
 181  * Other internal data (v->data, v->activeRegion, f->data, f->marked,
 182  * f->trail, e->winding) is set to zero.
 183  *
 184  * ********************** Basic Edge Operations **************************
 185  *
 186  * __gl_meshMakeEdge( mesh ) creates one edge, two vertices, and a loop.
 187  * The loop (face) consists of the two new half-edges.
 188  *
 189  * __gl_meshSplice( eOrg, eDst ) is the basic operation for changing the
 190  * mesh connectivity and topology.  It changes the mesh so that
 191  *      eOrg->Onext <- OLD( eDst->Onext )
 192  *      eDst->Onext <- OLD( eOrg->Onext )
 193  * where OLD(...) means the value before the meshSplice operation.
 194  *
 195  * This can have two effects on the vertex structure:
 196  *  - if eOrg->Org != eDst->Org, the two vertices are merged together
 197  *  - if eOrg->Org == eDst->Org, the origin is split into two vertices
 198  * In both cases, eDst->Org is changed and eOrg->Org is untouched.
 199  *
 200  * Similarly (and independently) for the face structure,
 201  *  - if eOrg->Lface == eDst->Lface, one loop is split into two
 202  *  - if eOrg->Lface != eDst->Lface, two distinct loops are joined into one
 203  * In both cases, eDst->Lface is changed and eOrg->Lface is unaffected.
 204  *
 205  * __gl_meshDelete( eDel ) removes the edge eDel.  There are several cases:
 206  * if (eDel->Lface != eDel->Rface), we join two loops into one; the loop
 207  * eDel->Lface is deleted.  Otherwise, we are splitting one loop into two;
 208  * the newly created loop will contain eDel->Dst.  If the deletion of eDel
 209  * would create isolated vertices, those are deleted as well.
 210  *
 211  * ********************** Other Edge Operations **************************
 212  *
 213  * __gl_meshAddEdgeVertex( eOrg ) creates a new edge eNew such that
 214  * eNew == eOrg->Lnext, and eNew->Dst is a newly created vertex.
 215  * eOrg and eNew will have the same left face.
 216  *
 217  * __gl_meshSplitEdge( eOrg ) splits eOrg into two edges eOrg and eNew,
 218  * such that eNew == eOrg->Lnext.  The new vertex is eOrg->Dst == eNew->Org.
 219  * eOrg and eNew will have the same left face.
 220  *
 221  * __gl_meshConnect( eOrg, eDst ) creates a new edge from eOrg->Dst
 222  * to eDst->Org, and returns the corresponding half-edge eNew.
 223  * If eOrg->Lface == eDst->Lface, this splits one loop into two,
 224  * and the newly created loop is eNew->Lface.  Otherwise, two disjoint
 225  * loops are merged into one, and the loop eDst->Lface is destroyed.
 226  *
 227  * ************************ Other Operations *****************************
 228  *
 229  * __gl_meshNewMesh() creates a new mesh with no edges, no vertices,
 230  * and no loops (what we usually call a "face").
 231  *
 232  * __gl_meshUnion( mesh1, mesh2 ) forms the union of all structures in
 233  * both meshes, and returns the new mesh (the old meshes are destroyed).
 234  *
 235  * __gl_meshDeleteMesh( mesh ) will free all storage for any valid mesh.
 236  *
 237  * __gl_meshZapFace( fZap ) destroys a face and removes it from the
 238  * global face list.  All edges of fZap will have a NULL pointer as their
 239  * left face.  Any edges which also have a NULL pointer as their right face
 240  * are deleted entirely (along with any isolated vertices this produces).
 241  * An entire mesh can be deleted by zapping its faces, one at a time,
 242  * in any order.  Zapped faces cannot be used in further mesh operations!
 243  *
 244  * __gl_meshCheckMesh( mesh ) checks a mesh for self-consistency.
 245  */
 246
 247 GLUhalfEdge     *__gl_meshMakeEdge( GLUmesh *mesh );
 248 int             __gl_meshSplice( GLUhalfEdge *eOrg, GLUhalfEdge *eDst );
 249 int             __gl_meshDelete( GLUhalfEdge *eDel );
 250
 251 GLUhalfEdge     *__gl_meshAddEdgeVertex( GLUhalfEdge *eOrg );
 252 GLUhalfEdge     *__gl_meshSplitEdge( GLUhalfEdge *eOrg );
 253 GLUhalfEdge     *__gl_meshConnect( GLUhalfEdge *eOrg, GLUhalfEdge *eDst );
 254
 255 GLUmesh         *__gl_meshNewMesh( void );
 256 GLUmesh         *__gl_meshUnion( GLUmesh *mesh1, GLUmesh *mesh2 );
 257 void            __gl_meshDeleteMesh( GLUmesh *mesh );
 258 void            __gl_meshZapFace( GLUface *fZap );
 259
 260 #ifdef NDEBUG
 261 #define         __gl_meshCheckMesh( mesh )
 262 #else
 263 void            __gl_meshCheckMesh( GLUmesh *mesh );
 264 #endif
 265
 266 #endif