qquickturbulence.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#undef QT_NO_FOREACH // this file contains unported legacy Q_FOREACH uses
 
#include "qquickturbulence_p.h"
#include "qquickparticlepainter_p.h"                           //TODO: Why was this needed again?
#include <cmath>
#include <cstdlib>
#include <QDebug>
#include <QQmlFile>
QT_BEGIN_NAMESPACE
 
/*!
    \qmltype Turbulence
    \nativetype QQuickTurbulenceAffector
    \inqmlmodule QtQuick.Particles
    \ingroup qtquick-particles
    \inherits ParticleAffector
    \brief Provides fluid-like forces from a noise image.
 
    The Turbulence Element scales the noise source over the area it affects,
    and uses the curl of that source to generate force vectors.
 
    Turbulence requires a fixed size. Unlike other affectors, a 0x0 Turbulence element
    will affect no particles.
 
    The source should be relatively smooth black and white noise, such as perlin noise.
*/
/*!
    \qmlproperty real QtQuick.Particles::Turbulence::strength
 
    The magnitude of the velocity vector at any point varies between zero and
    the square root of two. It will then be multiplied by strength to get the
    velocity per second for the particles affected by the turbulence.
*/
/*!
    \qmlproperty url QtQuick.Particles::Turbulence::noiseSource
 
    The source image to generate the turbulence from. It will be scaled to the size of the element,
    so equal or larger sizes will give better results. Tweaking this image is the only way to tweak
    behavior such as where vortices are or how many exist.
 
    The source should be a relatively smooth black and white noise image, such as perlin noise.
    A default image will be used if none is provided.
*/
 
QQuickTurbulenceAffector::QQuickTurbulenceAffector(QQuickItem *parent) :
    QQuickParticleAffector(parent),
    m_strength(10), m_gridSize(0), m_field(nullptr), m_vectorField(nullptr), m_inited(false)
{
}
 
void QQuickTurbulenceAffector::geometryChange(const QRectF &, const QRectF &)
{
    initializeGrid();
}
 
QQuickTurbulenceAffector::~QQuickTurbulenceAffector()
{
    if (m_field) {
        for (int i=0; i<m_gridSize; i++)
            free(m_field[i]);
        free(m_field);
    }
    if (m_vectorField) {
        for (int i=0; i<m_gridSize; i++)
            free(m_vectorField[i]);
        free(m_vectorField);
    }
}
 
void QQuickTurbulenceAffector::initializeGrid()
{
    if (!m_inited)
        return;
 
    int arg = qMax(width(), height());
    if (m_gridSize != arg) {
        if (m_field){ //deallocate and then reallocate grid
            for (int i=0; i<m_gridSize; i++)
                free(m_field[i]);
            free(m_field);
        }
        if (m_vectorField) {
            for (int i=0; i<m_gridSize; i++)
                free(m_vectorField[i]);
            free(m_vectorField);
        }
        m_gridSize = arg;
    }
 
    m_field = (qreal**)malloc(m_gridSize * sizeof(qreal*));
    for (int i=0; i<m_gridSize; i++)
        m_field[i] = (qreal*)malloc(m_gridSize * sizeof(qreal));
    m_vectorField = (QPointF**)malloc(m_gridSize * sizeof(QPointF*));
    for (int i=0; i<m_gridSize; i++)
        m_vectorField[i] = (QPointF*)malloc(m_gridSize * sizeof(QPointF));
 
    QImage image;
    if (!m_noiseSource.isEmpty())
        image = QImage(QQmlFile::urlToLocalFileOrQrc(m_noiseSource)).scaled(QSize(m_gridSize, m_gridSize));
    if (image.isNull())
        image = QImage(QStringLiteral(":particleresources/noise.png")).scaled(QSize(m_gridSize, m_gridSize));
 
    for (int i=0; i<m_gridSize; i++)
        for (int j=0; j<m_gridSize; j++)
            m_field[i][j] = qGray(image.pixel(QPoint(i,j)));
    for (int i=0; i<m_gridSize; i++){
        for (int j=0; j<m_gridSize; j++){
            m_vectorField[i][j].setX(boundsRespectingField(i-1,j) - boundsRespectingField(i,j));
            m_vectorField[i][j].setY(boundsRespectingField(i,j) - boundsRespectingField(i,j-1));
        }
    }
}
 
qreal QQuickTurbulenceAffector::boundsRespectingField(int x, int y)
{
    if (x < 0)
        x = 0;
    if (x >= m_gridSize)
        x = m_gridSize - 1;
    if (y < 0)
        y = 0;
    if (y >= m_gridSize)
        y = m_gridSize - 1;
    return m_field[x][y];
}
 
void QQuickTurbulenceAffector::ensureInit()
{
    if (m_inited)
        return;
    m_inited = true;
    initializeGrid();
}
 
void QQuickTurbulenceAffector::affectSystem(qreal dt)
{
    if (!m_system || !m_enabled)
        return;
    ensureInit();
    if (!m_gridSize)
        return;
 
    updateOffsets();//### Needed if an ancestor is transformed.
 
    QRect boundsRect(0,0,m_gridSize,m_gridSize);
    for (QQuickParticleGroupData *gd : m_system->groupData) {
        if (!activeGroup(gd->index))
            continue;
        foreach (QQuickParticleData *d, gd->data){
            if (!shouldAffect(d))
                continue;
            QPoint pos = (QPointF(d->curX(m_system), d->curY(m_system)) - m_offset).toPoint();
            if (!boundsRect.contains(pos,true))//Need to redo bounds checking due to quantization.
                continue;
            qreal fx = 0.0;
            qreal fy = 0.0;
            fx += m_vectorField[pos.x()][pos.y()].x() * m_strength;
            fy += m_vectorField[pos.x()][pos.y()].y() * m_strength;
            if (fx || fy){
                d->setInstantaneousVX(d->curVX(m_system)+ fx * dt, m_system);
                d->setInstantaneousVY(d->curVY(m_system)+ fy * dt, m_system);
                postAffect(d);
            }
        }
    }
}
 
QT_END_NAMESPACE
 
#include "moc_qquickturbulence_p.cpp"