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
|
#include <cmath>
#include <iostream>
#include <fstream>
#include <sys/stat.h>
#include <sys/types.h>
#include <sstream>
#include "vec3.h"
#include "curve.h"
using namespace std;
vec3 integrand(vec3 s, vec3 ds)
{
cout << "point " << s << "ds = " << ds << endl;
return ds;
}
vec3 point;
/* dl x r / (|r| ^ 2) */
vec3 dB(vec3 s, vec3 ds)
{
vec3 r = s - point;
scalar r2 = r.magnitudeSquared();
vec3 rnorm = r / std::sqrt(r2);
return ds.cross(rnorm) / r2;
}
/* dl * r / (|r| ^ 2) */
vec3 dE(vec3 s, vec3 ds)
{
vec3 r = point - s;
scalar r2 = r.magnitudeSquared();
vec3 rnorm = r / std::sqrt(r2);
return rnorm * ds.magnitude() / r2;
}
/* A current or charge distribution */
struct Entity {
enum { CHARGE, CURRENT } type;
};
Arc loop(vec3(0, 0, 0), vec3(0, 1, 0), vec3(1, 0, 0), M_PI * 2);
//Spiral loop(vec3(0, 0, 0), vec3(0, 1, 0), vec3(1, 0, 0), M_PI * 2 * 10, 1);
//LineSegment loop(vec3(-.1, .1, 0), vec3(.1, .1, 0));
//Toroid loop;
ostream *dump_ofs = NULL;
vec3 dump(vec3 s, vec3 ds)
{
*dump_ofs << s << " " << ds << endl;
//cout << "Magn: " << ds.magnitude() << endl;
return 0;
}
void dump_path(ostream &out, const Curve *c)
{
dump_ofs = &out;
c->integrate(dump, 1e-2);
}
/* dump the field (gnuplot format) at z = 0 */
/* requires x0 < x1, y0 < y1 */
const scalar U0 = 4e-7 * M_PI;
const scalar I = 1;
const scalar Q = 1;
const scalar C = 299792458;
const scalar E0 = 1 / ( U0 * C * C );
const scalar K_E = 1 / (4 * M_PI * E0);
void dump_field(scalar x0, scalar y0, scalar z0, scalar x1, scalar y1, scalar z1, scalar delta)
{
for(scalar z = z0; z <= z1; z += delta)
for(scalar y = y0; y <= y1; y += delta)
for(scalar x = x0; x <= x1; x += delta)
{
point = vec3(x, y, z);
vec3 B = loop.integrate(dE, 1e-1) * Q * K_E;
if(B.magnitude() > 1e-8)
{
B=B.normalize() / 10;
cout << point[0] << " " << point[1] << " " << point[2] << " ";
cout << B[0] << " " << B[1] << " " << B[2] << endl;
}
}
}
void dump_fieldline(ostream &out, vec3 x, scalar len)
{
point = x;
scalar delta = .1;
while(len > 0)
{
out << point << endl;
vec3 B = loop.integrate(dB, 1e-1) * U0 * I;
point += delta * B;
len -= delta;
}
}
void dump_values(vec3 start, vec3 del, int times)
{
point = start;
while(times--)
{
point += del;
}
}
int main(int argc, char *argv[])
{
//if(argc != 2)
// return 1;
//loop = Toroid(vec3(0, 0, 0), vec3(1, 0, 0), vec3(0, 0, 1), 1 * M_PI, .1, atof(argv[1]));
//LineSegment wire(vec3(0, -100, 0), vec3(0, 100, 0));
//std::cout << "length = " << loop.integrate(integrand, 1e-2) << endl;
//vec3 dx = .01;
//point = 0;
//scalar I = 1;
//for(int i = 0; i < 1000; i++, point += dx)
//std::cout << point[0] << " " << U0 / ( 4 * M_PI ) * loop.integrate(dB, 1e-2)[0] << endl;
dump_field(-3, -3, 0,
3, 3, 0,
.1);
//dump_field(0,0,0,0,0,0);
stringstream ss;
ss << "curve.fld";
ofstream ofs(ss.str());
dump_path(ofs, (Curve*)&loop);
ofs.close();
#if 0
mkdir("field", 0755);
for(scalar y = -1.5; y <= 1.5; y += .1)
{
stringstream ss;
ss << "field/" << y << ".fld";
ofstream ofs(ss.str());
dump_fieldline(ofs, vec3(0, y, 0), 10);
ofs.close();
}
#endif
}
|
