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/****************************************************************************
**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtQuick3D module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** GNU Lesser General Public License Usage
** This file may be used under the terms of the GNU Lesser General Public
** License version 2.1 as published by the Free Software Foundation and
** appearing in the file LICENSE.LGPL included in the packaging of this
** file. Please review the following information to ensure the GNU Lesser
** General Public License version 2.1 requirements will be met:
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU General
** Public License version 3.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of this
** file. Please review the following information to ensure the GNU General
** Public License version 3.0 requirements will be met:
** http://www.gnu.org/copyleft/gpl.html.
**
** Other Usage
** Alternatively, this file may be used in accordance with the terms and
** conditions contained in a signed written agreement between you and Nokia.
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "billboarditem3d.h"
#include "qgraphicsbillboardtransform.h"
/*!
\qmlclass BillboardItem3D BillboardItem3D
\brief The BillboardItem3D will always face toward the viewer.
\since 4.8
\ingroup qt3d::qml3d
Sometimes it is desirable to have objects which always face toward the
camera. For example, a quad with text on it may always face the camera
so as to be readable at all times.
While this can be achieved with a QGraphicsLookAtTransform on a normal
Item3D, the BillboardItem3D class provides a more efficient "cheat" which
takes advantage of the underlying 3D mathematics.
To use a BillboardItem3D declare it exactly like a regular Item3D. When
the item is drawn a QGraphicsBillboardTransform will be applied to the item
after all other transforms have been performed.
For example:
\code
Viewport {
BillboardItem3D {
mesh: Mesh { source: "model.obj" }
effect: Effect {
blending: true
texture: "texture.png"
}
}
}
\endcode
For a practical illustration of its use see the forest example.
*/
BillboardItem3D::BillboardItem3D(QObject *parent)
: QDeclarativeItem3D(parent)
{
m_preserveUpVector = false;
}
/*!
\qmlproperty bool BillboardItem3D::preserveUpVector
This property specifies whether the billboard transform should
preserve the "up vector" so that objects stay at right angles
to the ground plane in the scene.
The default value for this property is false, which indicates that
the object being transformed should always face directly to the camera
This is also known as a "spherical billboard".
If the value for this property is true, then the object will have
its up orientation preserved. This is also known as a "cylindrical
billboard".
*/
bool BillboardItem3D::preserveUpVector() const
{
return m_preserveUpVector;
}
void BillboardItem3D::setPreserveUpVector(bool value)
{
m_preserveUpVector = value;
update();
}
/*!
\internal
This replaces the standard draw() as used in Item3D. In this instance all drawing
carried out using \a painter follows the standard sequence. However, after the
transforms for the item have been applied, a QGraphicsBillboardTransform is applied
to the model-view matrix.
After the current item is drawn the model-view matrix from immediately before the
billboard transform being applied will be restored so child items are not affected by it.
*/
void BillboardItem3D::draw(QGLPainter *painter)
{
// Bail out if this item and its children have been disabled.
if (!isEnabled())
return;
if (!isInitialized())
initialize(painter);
//Setup picking
int prevId = painter->objectPickId();
painter->setObjectPickId(objectPickId());
//Setup effect (lighting, culling, effects etc)
const QGLLightParameters *currentLight = 0;
QMatrix4x4 currentLightTransform;
drawLightingSetup(painter, currentLight, currentLightTransform);
bool viewportBlend, effectBlend;
drawEffectSetup(painter, viewportBlend, effectBlend);
drawCullSetup();
//Local and Global transforms
drawTransformSetup(painter);
//After all of the other transforms, apply the billboard transform to
//ensure forward facing.
painter->modelViewMatrix().push();
QGraphicsBillboardTransform bill;
bill.setPreserveUpVector(m_preserveUpVector);
bill.applyTo(const_cast<QMatrix4x4 *>(&painter->modelViewMatrix().top()));
//Drawing
drawItem(painter);
//Pop the billboard transform from the model-view matrix stack so that it
//is not applied to child items.
painter->modelViewMatrix().pop();
//Draw children
drawChildren(painter);
//Cleanup
drawTransformCleanup(painter);
drawLightingCleanup(painter, currentLight, currentLightTransform);
drawEffectCleanup(painter, viewportBlend, effectBlend);
drawCullCleanup();
//Reset pick id.
painter->setObjectPickId(prevId);
}
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