| 1 | // Copyright (C) 2016 The Qt Company Ltd. |
|---|---|
| 2 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
| 3 | |
| 4 | #include "qquickfriction_p.h" |
| 5 | #include <qmath.h> |
| 6 | |
| 7 | QT_BEGIN_NAMESPACE |
| 8 | /*! |
| 9 | \qmltype Friction |
| 10 | \nativetype QQuickFrictionAffector |
| 11 | \inqmlmodule QtQuick.Particles |
| 12 | \ingroup qtquick-particles |
| 13 | \inherits ParticleAffector |
| 14 | \brief For applying friction proportional to the particle's current velocity. |
| 15 | |
| 16 | */ |
| 17 | |
| 18 | /*! |
| 19 | \qmlproperty real QtQuick.Particles::Friction::factor |
| 20 | |
| 21 | A drag will be applied to moving objects which is this factor of their current velocity. |
| 22 | */ |
| 23 | /*! |
| 24 | \qmlproperty real QtQuick.Particles::Friction::threshold |
| 25 | |
| 26 | The drag will only be applied to objects with a velocity above the threshold velocity. The |
| 27 | drag applied will bring objects down to the threshold velocity, but no further. |
| 28 | |
| 29 | The default threshold is 0 |
| 30 | */ |
| 31 | static qreal sign(qreal a) |
| 32 | { |
| 33 | return a >= 0 ? 1 : -1; |
| 34 | } |
| 35 | |
| 36 | static const qreal epsilon = 0.00001; |
| 37 | |
| 38 | QQuickFrictionAffector::QQuickFrictionAffector(QQuickItem *parent) : |
| 39 | QQuickParticleAffector(parent), m_factor(0.0), m_threshold(0.0) |
| 40 | { |
| 41 | } |
| 42 | |
| 43 | bool QQuickFrictionAffector::affectParticle(QQuickParticleData *d, qreal dt) |
| 44 | { |
| 45 | if (!m_factor) |
| 46 | return false; |
| 47 | qreal curVX = d->curVX(particleSystem: m_system); |
| 48 | qreal curVY = d->curVY(particleSystem: m_system); |
| 49 | if (!curVX && !curVY) |
| 50 | return false; |
| 51 | qreal newVX = curVX + (curVX * m_factor * -1 * dt); |
| 52 | qreal newVY = curVY + (curVY * m_factor * -1 * dt); |
| 53 | |
| 54 | if (!m_threshold) { |
| 55 | if (sign(a: curVX) != sign(a: newVX)) |
| 56 | newVX = 0; |
| 57 | if (sign(a: curVY) != sign(a: newVY)) |
| 58 | newVY = 0; |
| 59 | } else { |
| 60 | qreal curMag = qSqrt(v: curVX*curVX + curVY*curVY); |
| 61 | if (curMag <= m_threshold + epsilon) |
| 62 | return false; |
| 63 | qreal newMag = qSqrt(v: newVX*newVX + newVY*newVY); |
| 64 | if (newMag <= m_threshold + epsilon || //went past the threshold, stop there instead |
| 65 | sign(a: curVX) != sign(a: newVX) || //went so far past maybe it came out the other side! |
| 66 | sign(a: curVY) != sign(a: newVY)) { |
| 67 | qreal theta = qAtan2(y: curVY, x: curVX); |
| 68 | newVX = m_threshold * qCos(v: theta); |
| 69 | newVY = m_threshold * qSin(v: theta); |
| 70 | } |
| 71 | } |
| 72 | |
| 73 | d->setInstantaneousVX(vx: newVX, particleSystem: m_system); |
| 74 | d->setInstantaneousVY(vy: newVY, particleSystem: m_system); |
| 75 | return true; |
| 76 | } |
| 77 | QT_END_NAMESPACE |
| 78 | |
| 79 | #include "moc_qquickfriction_p.cpp" |
| 80 |