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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 "qglsphere.h"
#include "qglbuilder.h"
#include <QtCore/qmath.h>
QT_BEGIN_NAMESPACE
/*!
\class QGLSphere
\brief The QGLSphere class represents the geometry of a simple sphere in 3D space.
\since 4.8
\ingroup qt3d
\ingroup qt3d::geometry
The following example creates a sphere of 2 units in diameter and
draws it at (10, 25, 0) in a QGLPainter:
\code
QGLBuilder builder;
builder << QGLSphere(2);
QGLSceneNode *node = builder.finalizedSceneNode();
painter.translate(10, 25, 0);
node->draw(&painter);
\endcode
The QGLSphere class specifies positions, normals and 2D texture
co-ordinates for all of the vertices that make up the sphere.
The texture co-ordinates are fixed at construction time. This
is because constructing the sphere can involve generating additional
vertices which need to interpolate the texture co-ordinates of their
neighboring vertices.
The default mode of QGLSphere is a "UV sphere", which divides the
sphere up into longitudinal and latitudinal sections. The longitudinal
slices meet at the poles, which in a single unit sphere are defined to
be at (0, 0, +0.5) and (0, 0, -0.5). This choice is the simplest to
texture map as the texture will only distort along the x-axis of the
2D texture. However the density of vertices is significantly higher at
the poles than it is elsewhere on the sphere and is a poor choice if a
uniform density of pixels from the texture map is required.
\sa QGLBuilder
*/
/*!
\fn QGLSphere::QGLSphere(qreal diameter, int depth)
Creates a sphere of \a diameter across (default is 1). When the sphere
is recursively subdivided into triangles, it will be subdivided no more
than \a depth times (between 1 and 10, default is 5).
*/
/*!
Destroys this sphere object.
*/
QGLSphere::~QGLSphere()
{
}
/*!
\fn qreal QGLSphere::diameter() const
Returns the diameter of this sphere. The default is 1.
\sa setDiameter()
*/
/*!
\fn void QGLSphere::setDiameter(qreal diameter)
Sets the diameter of this sphere to \a diameter.
\sa diameter()
*/
/*!
\fn int QGLSphere::subdivisionDepth() const
Returns the maximum depth when this sphere is subdivided into triangles.
The default is 5. The following picture shows the effect of depth
values between 1 and 10 for a UV sphere:
\image sphere-detail.png
\table
\header \o Level of Detail \o Number of Triangles
\row \o 1 \o 64
\row \o 2 \o 128
\row \o 3 \o 256
\row \o 4 \o 512
\row \o 5 \o 1024
\row \o 6 \o 2048
\row \o 7 \o 4096
\row \o 8 \o 8192
\row \o 9 \o 16384
\row \o 10 \o 32768
\endtable
\sa setSubdivisionDepth()
*/
/*!
\fn void QGLSphere::setSubdivisionDepth(int depth)
Sets the maximum \a depth when this sphere is subdivided into triangles.
\sa subdivisionDepth()
*/
/*!
\relates QGLSphere
Builds the geometry for \a sphere within the specified
geometry \a builder.
*/
QGLBuilder& operator<<(QGLBuilder& builder, const QGLSphere& sphere)
{
qreal radius = sphere.diameter() / 2.0f;
// Determine the number of slices and stacks to generate.
static int const slicesAndStacks[] = {
8, 4,
8, 8,
16, 8,
16, 16,
32, 16,
32, 32,
64, 32,
64, 64,
128, 64,
128, 128
};
int divisions = sphere.subdivisionDepth();
if (divisions < 1)
divisions = 1;
else if (divisions > 10)
divisions = 10;
int stacks = slicesAndStacks[divisions * 2 - 1];
int slices = slicesAndStacks[divisions * 2 - 2];
// Precompute sin/cos values for the slices and stacks.
const int maxSlices = 128 + 1;
const int maxStacks = 128 + 1;
qreal sliceSin[maxSlices];
qreal sliceCos[maxSlices];
qreal stackSin[maxStacks];
qreal stackCos[maxStacks];
for (int slice = 0; slice < slices; ++slice) {
qreal angle = 2 * M_PI * slice / slices;
sliceSin[slice] = qFastSin(angle);
sliceCos[slice] = qFastCos(angle);
}
sliceSin[slices] = sliceSin[0]; // Join first and last slice.
sliceCos[slices] = sliceCos[0];
for (int stack = 0; stack <= stacks; ++stack) {
qreal angle = M_PI * stack / stacks;
stackSin[stack] = qFastSin(angle);
stackCos[stack] = qFastCos(angle);
}
stackSin[0] = 0.0f; // Come to a point at the poles.
stackSin[stacks] = 0.0f;
// Create the stacks.
for (int stack = 0; stack < stacks; ++stack) {
QGeometryData prim;
qreal z = radius * stackCos[stack];
qreal nextz = radius * stackCos[stack + 1];
qreal s = stackSin[stack];
qreal nexts = stackSin[stack + 1];
qreal c = stackCos[stack];
qreal nextc = stackCos[stack + 1];
qreal r = radius * s;
qreal nextr = radius * nexts;
for (int slice = 0; slice <= slices; ++slice) {
prim.appendVertex
(QVector3D(nextr * sliceSin[slice],
nextr * sliceCos[slice], nextz));
prim.appendNormal
(QVector3D(sliceSin[slice] * nexts,
sliceCos[slice] * nexts, nextc));
prim.appendTexCoord
(QVector2D(1.0f - qreal(slice) / slices,
1.0f - qreal(stack + 1) / stacks));
prim.appendVertex
(QVector3D(r * sliceSin[slice],
r * sliceCos[slice], z));
prim.appendNormal
(QVector3D(sliceSin[slice] * s,
sliceCos[slice] * s, c));
prim.appendTexCoord
(QVector2D(1.0f - qreal(slice) / slices,
1.0f - qreal(stack) / stacks));
}
builder.addQuadStrip(prim);
}
return builder;
}
QT_END_NAMESPACE
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