1/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2010 Robert Osfield
2 *
3 * This library is open source and may be redistributed and/or modified under
4 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
5 * (at your option) any later version.  The full license is in LICENSE file
6 * included with this distribution, and on the openscenegraph.org website.
7 *
8 * This library is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11 * OpenSceneGraph Public License for more details.
12*/
13// Written by Wang Rui, (C) 2010
14
15#ifndef OSGPARTICLE_ANGULARDAMPINGOPERATOR
16#define OSGPARTICLE_ANGULARDAMPINGOPERATOR
17
18#include <osgParticle/Operator>
19#include <osgParticle/Particle>
20
21namespace osgParticle
22{
23
24
25/** A angular damping operator applies damping constant to particle's angular velocity.
26    Refer to David McAllister's Particle System API (http://www.particlesystems.org)
27*/
28class AngularDampingOperator : public Operator
29{
30public:
31    AngularDampingOperator() : Operator(), _cutoffLow(0.0f), _cutoffHigh(FLT_MAX)
32    {}
33
34    AngularDampingOperator( const AngularDampingOperator& copy, const osg::CopyOp& copyop = osg::CopyOp::SHALLOW_COPY )
35    :   Operator(copy, copyop), _damping(copy._damping),
36        _cutoffLow(copy._cutoffLow), _cutoffHigh(copy._cutoffHigh)
37    {}
38
39    META_Object( osgParticle, AngularDampingOperator );
40
41    /// Set the damping factors
42    void setDamping( float x, float y, float z ) { _damping.set(x, y, z); }
43    void setDamping( const osg::Vec3& damping ) { _damping = damping; }
44
45    /// Set the damping factors to one value
46    void setDamping( float x ) { _damping.set(x, x, x); }
47
48    /// Get the damping factors
49    void getDamping( float& x, float& y, float& z ) const
50    { x = _damping.x(); y = _damping.y(); z = _damping.z(); }
51
52    const osg::Vec3& getDamping() const { return _damping; }
53
54    /// Set the velocity cutoff factors
55    void setCutoff( float low, float high ) { _cutoffLow = low; _cutoffHigh = high; }
56    void setCutoffLow( float low ) { _cutoffLow = low; }
57    void setCutoffHigh( float low ) { _cutoffHigh = low; }
58
59    /// Get the velocity cutoff factors
60    void getCutoff( float& low, float& high ) const { low = _cutoffLow; high = _cutoffHigh; }
61    float getCutoffLow() const { return _cutoffLow; }
62    float getCutoffHigh() const { return _cutoffHigh; }
63
64    /// Apply the acceleration to a particle. Do not call this method manually.
65    inline void operate( Particle* P, double dt );
66
67protected:
68    virtual ~AngularDampingOperator() {}
69    AngularDampingOperator& operator=( const AngularDampingOperator& ) { return *this; }
70
71    osg::Vec3 _damping;
72    float _cutoffLow;
73    float _cutoffHigh;
74};
75
76// INLINE METHODS
77
78inline void AngularDampingOperator::operate( Particle* P, double dt )
79{
80    const osg::Vec3& vel = P->getAngularVelocity();
81    float length2 = vel.length2();
82    if ( length2>=_cutoffLow && length2<=_cutoffHigh )
83    {
84        osg::Vec3 newvel( vel.x() * (1.0f - (1.0f - _damping.x()) * dt),
85                          vel.y() * (1.0f - (1.0f - _damping.y()) * dt),
86                          vel.z() * (1.0f - (1.0f - _damping.z()) * dt) );
87        P->setAngularVelocity( newvel );
88    }
89}
90
91
92}
93
94#endif
95