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
|
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtQuick module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qquickfriction_p.h"
#include <qmath.h>
QT_BEGIN_NAMESPACE
/*!
\qmltype Friction
\instantiates QQuickFrictionAffector
\inqmlmodule QtQuick.Particles
\ingroup qtquick-particles
\inherits Affector
\brief For applying friction proportional to the particle's current velocity.
*/
/*!
\qmlproperty real QtQuick.Particles::Friction::factor
A drag will be applied to moving objects which is this factor of their current velocity.
*/
/*!
\qmlproperty real QtQuick.Particles::Friction::threshold
The drag will only be applied to objects with a velocity above the threshold velocity. The
drag applied will bring objects down to the threshold velocity, but no further.
The default threshold is 0
*/
static qreal sign(qreal a)
{
return a >= 0 ? 1 : -1;
}
static const qreal epsilon = 0.00001;
QQuickFrictionAffector::QQuickFrictionAffector(QQuickItem *parent) :
QQuickParticleAffector(parent), m_factor(0.0), m_threshold(0.0)
{
}
bool QQuickFrictionAffector::affectParticle(QQuickParticleData *d, qreal dt)
{
if (!m_factor)
return false;
qreal curVX = d->curVX(m_system);
qreal curVY = d->curVY(m_system);
if (!curVX && !curVY)
return false;
qreal newVX = curVX + (curVX * m_factor * -1 * dt);
qreal newVY = curVY + (curVY * m_factor * -1 * dt);
if (!m_threshold) {
if (sign(curVX) != sign(newVX))
newVX = 0;
if (sign(curVY) != sign(newVY))
newVY = 0;
} else {
qreal curMag = qSqrt(curVX*curVX + curVY*curVY);
if (curMag <= m_threshold + epsilon)
return false;
qreal newMag = qSqrt(newVX*newVX + newVY*newVY);
if (newMag <= m_threshold + epsilon || //went past the threshold, stop there instead
sign(curVX) != sign(newVX) || //went so far past maybe it came out the other side!
sign(curVY) != sign(newVY)) {
qreal theta = qAtan2(curVY, curVX);
newVX = m_threshold * qCos(theta);
newVY = m_threshold * qSin(theta);
}
}
d->setInstantaneousVX(newVX, m_system);
d->setInstantaneousVY(newVY, m_system);
return true;
}
QT_END_NAMESPACE
#include "moc_qquickfriction_p.cpp"
|
