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/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
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** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
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****************************************************************************/
/*!
\example multiviewport
\title Qt 3D: Multi Viewport QML Example
\ingroup qt3d-examples-qml
\brief A QML example that demonstrates rendering a Scenegraph from multiple
viewports.
\image multiviewport-qml-example.jpg
\e {Multi Viewport} renders a Scenegraph from the point of view of four
virtual cameras into the four quadrants of a window. This is a common
configuration for 3D CAD or modelling tools or could be adjusted to help
with rendering a rear-view mirror in a car racing game or a CCTV camera
display.
For more information, see \l{A Multi Viewport FrameGraph}.
\include examples-run.qdocinc
\section1 Creating Multiple RenderViews
Using the rules defined in \l {Framegraph Rules}, we construct five
RenderView objects from the FrameGraph:
\quotefromfile multiviewport/QuadViewportFrameGraph.qml
\skipto Viewport {
\printuntil /^\}/
The \e {order is important}. If the ClearBuffers node were to be the last
instead of the first, this would result in a black screen for the simple
reason that everything would be cleared right after having been so carefully
rendered. For a similar reason, it could not be used as the root of the
FrameGraph as that would result in a call to clear the whole screen for each
of our viewports.
Although the declaration order of the FrameGraph is important, Qt 3D is able
to process each RenderView in parallel as each RenderView is independent of
the others for the purposes of generating a set of RenderCommands to be
submitted whilst the RenderView's state is in effect.
Qt 3D uses a task-based approach to parallelism which naturally scales up
with the number of available cores. The RenderCommands for the RenderViews
can be generated in parallel across many cores, and as long as we take care
to submit the RenderViews in the correct order on the dedicated OpenGL
submission thread, the resulting scene will be rendered correctly.
*/
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