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
|
#include <Alib.h>
#include <stdio.h>
/*
* makeET : build an edge table based on edge coherence as described by
* Salmon and Slater, 1987.
*/
int
MakeET(AWindow * w, Point * pts, int npts, ZInfo * zinfo)
{
int i, t, addedEdge = 0;
long x1, y1, x2, y2;
long ymin, ymax;
Edge *e;
ymin = 0x7FFFFFFF;
ymax = 0x80000000;
zinfo->next = NotAnElement;
/*
* Process each edge in this polygon
*/
for (i = 1; i <= npts; ++i) {
/*
* Determine the end-points of this edge (x1, y1), (x2, y2).
*/
if (i == npts) {
x2 = pts[0].x;
y2 = pts[0].y;
}
else {
x2 = pts[i].x;
y2 = pts[i].y;
}
x1 = pts[i - 1].x;
y1 = pts[i - 1].y;
if (y1 > y2) {
t = x1;
x1 = x2;
x2 = t;
t = y1;
y1 = y2;
y2 = t;
}
/*
* This hack allows 3d polygon clipping to function ...
*/
if (y1 == -1) {
y1 = 0;
}
if (y1 < 0 || y2 >= w->height) {
fprintf(stderr, "polygon edge y out %d %d\n", y1, y2);
continue;
}
#ifdef DEBUG
fprintf(stderr, "edge (%d, %d) to (%d, %d)\n", x1, y1, x2, y2);
#endif
if (y1 != y2) {
if (w->EPTop == w->EPSize) {
fprintf(stderr, "Edge Pool Overflow\n");
return -1;
}
e = &(w->edgePool[(w->EPTop)++]);
e->y2 = (short) y2;
#ifdef FLOAT_SLOPE
e->x1 = x1;
e->Dx = (x2 - x1) / (y2 - y1);
#else
e->x1 = x1 << 16;
e->Dx = ((x2 - x1) << 16) / (y2 - y1);
#endif
e->p = zinfo;
e->nexte = w->edges[y1].head;
w->edges[y1].head = e;
addedEdge = 1;
if (y1 < ymin)
ymin = y1;
if (y2 > ymax)
ymax = y2;
}
}
if (addedEdge == 1) {
if (w->ymin > ymin)
w->ymin = (short) ymin;
if (w->ymax < ymax)
w->ymax = (short) ymax;
#ifdef DEBUG
fprintf(stderr, "ymin = %d, ymax = %d\n", ymin, ymax);
for (i = ymin; i <= ymax; ++i) {
if (w->edges[i].head == NULL)
fprintf(stderr, "[%d] (null)\n", i);
else {
fprintf(stderr, "[%d]\n", i);
for (e = w->edges[i].head; e != NULL; e = e->nexte)
fprintf(stderr, " x = %d, y2 = %d, Dx = 0x%x\n",
e->x1 >> 16, e->y2, e->Dx);
}
}
#endif
}
return 0;
}
|
