ReactOS  0.4.13-dev-249-gcba1a2f
mesh.h
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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 
248 int __gl_meshSplice( GLUhalfEdge *eOrg, GLUhalfEdge *eDst );
249 int __gl_meshDelete( GLUhalfEdge *eDel );
250 
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
double GLdouble
Definition: gl.h:163
GLUface * prev
Definition: mesh.h:128
int __gl_meshSplice(GLUhalfEdge *eOrg, GLUhalfEdge *eDst)
Definition: mesh.c:328
ActiveRegion * activeRegion
Definition: mesh.h:147
Definition: mesh.h:163
void __gl_meshDeleteMesh(GLUmesh *mesh)
Definition: mesh.c:711
GLUhalfEdge * Lnext
Definition: mesh.h:142
GLUvertex * prev
Definition: mesh.h:116
long pqHandle
Definition: mesh.h:123
GLUmesh * __gl_meshNewMesh(void)
Definition: mesh.c:603
GLUvertex * Org
Definition: mesh.h:143
GLUmesh * __gl_meshUnion(GLUmesh *mesh1, GLUmesh *mesh2)
Definition: mesh.c:655
GLUface * next
Definition: mesh.h:127
GLUhalfEdge * __gl_meshSplitEdge(GLUhalfEdge *eOrg)
Definition: mesh.c:475
GLUvertex vHead
Definition: mesh.h:164
void * data
Definition: mesh.h:118
GLuint coords
Definition: glext.h:7368
Definition: mesh.h:126
GLUhalfEdge eHeadSym
Definition: mesh.h:167
GLUhalfEdge * anEdge
Definition: mesh.h:129
unsigned char GLboolean
Definition: gl.h:151
GLUface * trail
Definition: mesh.h:133
void __gl_meshCheckMesh(GLUmesh *mesh)
Definition: mesh.c:742
GLUface fHead
Definition: mesh.h:165
GLUhalfEdge eHead
Definition: mesh.h:166
GLdouble t
Definition: mesh.h:122
GLUhalfEdge * Onext
Definition: mesh.h:141
void * data
Definition: mesh.h:130
GLUhalfEdge * __gl_meshAddEdgeVertex(GLUhalfEdge *eOrg)
Definition: mesh.c:446
GLUface * Lface
Definition: mesh.h:144
int winding
Definition: mesh.h:148
GLboolean marked
Definition: mesh.h:134
GLdouble s
Definition: mesh.h:122
GLUhalfEdge * Sym
Definition: mesh.h:140
GLUhalfEdge * __gl_meshConnect(GLUhalfEdge *eOrg, GLUhalfEdge *eDst)
Definition: mesh.c:508
GLUhalfEdge * next
Definition: mesh.h:139
void __gl_meshZapFace(GLUface *fZap)
Definition: mesh.c:555
GLUvertex * next
Definition: mesh.h:115
GLUhalfEdge * __gl_meshMakeEdge(GLUmesh *mesh)
Definition: mesh.c:275
GLboolean inside
Definition: mesh.h:135
int __gl_meshDelete(GLUhalfEdge *eDel)
Definition: mesh.c:384
GLUhalfEdge * anEdge
Definition: mesh.h:117