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/**
* @file head.cpp
* @brief Head class implementation
*
* $LicenseInfo:firstyear=2000&license=viewergpl$
*
* Copyright (c) 2000-2008, Linden Research, Inc.
*
* Second Life Viewer Source Code
* 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://secondlifegrid.net/programs/open_source/licensing/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://secondlifegrid.net/programs/open_source/licensing/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.
* $/LicenseInfo$
*/
// 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);
}
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