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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. |
| */ |