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
|
/**
* @file head.cpp
* @brief Head class implementation
*
* Copyright (c) 2000-2007, Linden Research, Inc.
*
* The source code in this file ("Source Code") is provided by Linden Lab
* to you under the terms of the GNU General Public License, version 2.0
* ("GPL"), unless you have obtained a separate licensing agreement
* ("Other License"), formally executed by you and Linden Lab. Terms of
* the GPL can be found in doc/GPL-license.txt in this distribution, or
* online at http://secondlife.com/developers/opensource/gplv2
*
* There are special exceptions to the terms and conditions of the GPL as
* it is applied to this Source Code. View the full text of the exception
* in the file doc/FLOSS-exception.txt in this software distribution, or
* online at http://secondlife.com/developers/opensource/flossexception
*
* By copying, modifying or distributing this software, you acknowledge
* that you have read and understood your obligations described above,
* and agree to abide by those obligations.
*
* ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
* WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
* COMPLETENESS OR PERFORMANCE.
*/
// implementation of a class that models the motion of a human head.
// The physics aren't quite right, but it will suffice for right now.
#include "llviewerprecompiledheaders.h"
#include "head.h"
#ifndef PI
#define PI ((F32) 3.14159265358979323846264338327)
#endif
// The friction force of the neck is modeled as:
// friction = -E*phi_dot - F*phi_dot (for positive phi_dot)
#define E1 0.75
#define F1 0.0
// TODO -- use the other PI defined in the math libs somewhere.
// --------------------------------------------------
// Misc. function delclarations...
// --------------------------------------------------
F32 phi_spring(F32 phi, F32 theta);
F32 theta_spring(F32 theta, F32 phi);
// --------------------------------------------------
// Class Head member functions...
// --------------------------------------------------
Head::Head() {
mass = 1.0f;
radius = 1.0f;
inertia = 2.0f * mass * radius * radius / 5.0f;
phi = 0.0f;
theta = 0.0f;
//gettimeofday(&t, &tz);
}
Head::Head(F32 m, F32 r) {
mass = m;
radius = r;
inertia = 2.0f * mass * radius * radius / 5.0f;
phi = 0.0f;
theta = 0.0f;
//gettimeofday(&t, &tz);
}
F32 Head::setMass(F32 m) {
mass = m;
inertia = 2.0f * mass * radius * radius / 5.0f;
return mass;
}
F32 Head::setRadius(F32 r) {
radius = r;
inertia = 2.0f * mass * radius * radius / 5.0f;
return radius;
}
F32 Head::getMass() { return mass; }
F32 Head::getRadius() { return radius; }
F32 Head::getInertia() { return inertia; }
void Head::propagate(F32 horizontal_force, F32 vertical_force, F32 dt) {
//struct timeval t1;
//F32 dt, temp;
F32 phi_torque, theta_torque;
F32 phi_dot, theta_dot;
//gettimeofday(&t1, &tz);
//dt = ((t1.tv_sec - t.tv_sec) * 1000000.0 + (t1.tv_usec - t.tv_usec)) / 1000000.0;
//dt = 0.033; // This is a kluge to prevent instabilities when using a stepper
// Calculate the return forces...
// Note: horizontal_force is positive toward right, so it's resultant torque
// is negative, since the phi spin angle is out the top of the head (using
// right-hand rule).
phi_torque = radius * (phi_spring(phi, theta) - horizontal_force);
theta_torque = radius * (theta_spring(phi, theta) + vertical_force);
// Propagate phi...
phi_dot = dt * phi_torque / inertia;
phi += dt * phi_dot;
if (phi >= PI/2.0f) {
phi = PI/2.0f;
}
else if (phi <= -PI/2.0f) {
phi = -PI/2.0f;
}
// Propagate theta...
theta_dot = dt * theta_torque / inertia;
theta += dt * theta_dot;
if (theta >= PI/2.0f) {
theta = PI/2.0f;
}
else if (theta <= -PI/2.0f) {
theta = -PI/2.0f;
}
//t = t1;
return;
}
F32 phi_spring(F32 phi, F32 theta) {
// The srping force is linear with -phi and the magnitude of theta.
F32 phi_force;
phi_force = - 30 * phi;
phi_force = phi_force * (1.0f + (F32)fabs(theta) / PI);
return phi_force;
}
F32 theta_spring(F32 phi, F32 theta) {
return phi_spring(theta, phi);
}
|
