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
|
// Quelle: http://reality.sgi.com/employees/atul_asd/code/chapter.html
#include "triangul.h"
#include <string.h>
static int initialise(n)
int n;
{
int i;
for (i = 1; i <= n; i++)
seg[i].is_inserted = FALSE;
generate_random_ordering(n);
return 0;
}
#ifdef STANDALONE
int main(argc, argv)
int argc;
char *argv[];
{
int n, nmonpoly, genus;
int op[SEGSIZE][3], i, ntriangles;
if ((argc < 2) || ((n = read_segments(argv[1], &genus)) < 0))
{
fprintf(stderr, "usage: triangulate <filename>\n");
exit(1);
}
initialise(n);
construct_trapezoids(n);
nmonpoly = monotonate_trapezoids(n);
ntriangles = triangulate_monotone_polygons(n, nmonpoly, op);
for (i = 0; i < ntriangles; i++)
printf("triangle #%d: %d %d %d\n", i,
op[i][0], op[i][1], op[i][2]);
return 0;
}
#else /* Not standalone. Use this as an interface routine */
/* Input specified as contours.
* Outer contour must be anti-clockwise.
* All inner contours must be clockwise.
*
* Every contour is specified by giving all its points in order. No
* point shoud be repeated. i.e. if the outer contour is a square,
* only the four distinct endpoints shopudl be specified in order.
*
* ncontours: #contours
* cntr: An array describing the number of points in each
* contour. Thus, cntr[i] = #points in the i'th contour.
* vertices: Input array of vertices. Vertices for each contour
* immediately follow those for previous one. Array location
* vertices[0] must NOT be used (i.e. i/p starts from
* vertices[1] instead. The output triangles are
* specified w.r.t. the indices of these vertices.
* triangles: Output array to hold triangles.
*
* Enough space must be allocated for all the arrays before calling
* this routine
*/
int triangulate_polygon(ncontours, cntr, vertices, triangles)
int ncontours;
int cntr[];
double (*vertices)[2];
int (*triangles)[3];
{
int i;
int nmonpoly, ccount, npoints, genus;
int n;
memset((void *)seg, 0, sizeof(seg));
ccount = 0;
i = 1;
while (ccount < ncontours)
{
int j;
int first, last;
npoints = cntr[ccount];
first = i;
last = first + npoints - 1;
for (j = 0; j < npoints; j++, i++)
{
seg[i].v0.x = vertices[i][0];
seg[i].v0.y = vertices[i][1];
if (i == last)
{
seg[i].next = first;
seg[i].prev = i-1;
seg[i-1].v1 = seg[i].v0;
}
else if (i == first)
{
seg[i].next = i+1;
seg[i].prev = last;
seg[last].v1 = seg[i].v0;
}
else
{
seg[i].prev = i-1;
seg[i].next = i+1;
seg[i-1].v1 = seg[i].v0;
}
seg[i].is_inserted = FALSE;
}
ccount++;
}
genus = ncontours - 1;
n = i-1;
initialise(n);
construct_trapezoids(n);
nmonpoly = monotonate_trapezoids(n);
triangulate_monotone_polygons(n, nmonpoly, triangles);
return 0;
}
/* This function returns TRUE or FALSE depending upon whether the
* vertex is inside the polygon or not. The polygon must already have
* been triangulated before this routine is called.
* This routine will always detect all the points belonging to the
* set (polygon-area - polygon-boundary). The return value for points
* on the boundary is not consistent!!!
*/
int is_point_inside_polygon(vertex)
double vertex[2];
{
point_t v;
int trnum, rseg;
trap_t *t;
v.x = vertex[0];
v.y = vertex[1];
trnum = locate_endpoint(&v, &v, 1);
t = &tr[trnum];
if (t->state == ST_INVALID)
return FALSE;
if ((t->lseg <= 0) || (t->rseg <= 0))
return FALSE;
rseg = t->rseg;
return _greater_than_equal_to(&seg[rseg].v1, &seg[rseg].v0);
}
#endif /* STANDALONE */
|
