summaryrefslogtreecommitdiff
path: root/src/glu/sgi/libtess/mesh.h
blob: 299b1bacb0840016f7d2b2f802464239d0af1864 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
/*
** License Applicability. Except to the extent portions of this file are
** made subject to an alternative license as permitted in the SGI Free
** Software License B, Version 1.1 (the "License"), the contents of this
** file are subject only to the provisions of the License. You may not use
** this file except in compliance with the License. You may obtain a copy
** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
** 
** http://oss.sgi.com/projects/FreeB
** 
** Note that, as provided in the License, the Software is distributed on an
** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
** PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
** 
** Original Code. The Original Code is: OpenGL Sample Implementation,
** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
** Copyright in any portions created by third parties is as indicated
** elsewhere herein. All Rights Reserved.
** 
** Additional Notice Provisions: The application programming interfaces
** established by SGI in conjunction with the Original Code are The
** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
** Window System(R) (Version 1.3), released October 19, 1998. This software
** was created using the OpenGL(R) version 1.2.1 Sample Implementation
** published by SGI, but has not been independently verified as being
** compliant with the OpenGL(R) version 1.2.1 Specification.
**
*/
/*
** 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