qt-everywhere-src-5.15.1/qt3d/examples/qt3d/scene2d/doc/src/scene2d.qdoc

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/*!
    \example scene2d
    \title Qt 3D: Scene2D QML Example
    \ingroup qt3d-examples-qml
    \brief A QML application that demonstrates using Qt Quick 2 within a Qt 3D scene.

    \image scene2d.png

    \e {Scene2D} demonstrates rendering a Qt Quick 2 scene into a texture and utilising
    the texture within a Qt 3D application including handling mouse events. The 3D scene
    contains a single active camera and renders a 3D Qt logo along with some controls
    declared with Qt Quick Controls.

    \include examples-run.qdocinc

    \section1 Setting up the 3D Scene

    We set up the 3D scene in an Entity that acts as the root of the object tree. The
    virtual camera is specified in \e main.qml:

    \quotefromfile scene2d/main.qml
    \skipto Camera {
    \printuntil }

    The RenderSettings specify the rendering algorithm used and also enable triangle
    based picking which is needed to properly handle mouse events when projecting a
    Qt Quick scene onto 3D geometry:

    \skipto RenderSettings {
    \printuntil }
    \printuntil }

    The 3D Qt logo that will be controlled by the controls in the Qt Quick scene is
    declared with:

    \skipto Entity {
    \printuntil }
    \printuntil }
    \printuntil }
    \printuntil }

    It simply consists of a Mesh component to load the geometry; a PhongMaterial component
    to give it a surface appearance, and a Transform component to specify its postion,
    orientation, and scale. The properties of these components are bound to properties
    on the logoControls element which we will discuss next.

    \section1 Rendering Qt Quick into a Texture

    We begin by declaring the Entity that will become our control panel. It consists of
    a CuboidMesh onto which we will place the texture containing a rendering of the Qt Quick
    scene. In this case we are using a simple cube for the geometry, but we could use
    any valid 3D geometry as long as it has texture coordinates. The texture coordinates
    are used for projecting the texture onto the 3D surface, and also for calculating the
    coordinates of mouse events to be passed to the originating Qt Quick scene.

    \skipto Entity {
    \printto Behavior
    \skipto Transform {
    \printuntil }
    \printuntil }

    We also include an ObjectPicker component so that we can interact with the controls
    using the mouse:

    \skipto ObjectPicker {
    \printuntil }
    \printuntil }
    \printuntil }

    For this example we have chosen to use an interaction mechanism whereby you must
    explicitly middle-click the controls to enable them.

    To apply the texture to the mesh, we make use of the built in TextureMaterial:

    \skipto TextureMaterial
    \printuntil }

    The final remaining piece is how to render the above texture from a Qt Quick scene.
    This is done with the Scene2D element:

    \skipto Scene2D
    \printto }
    \printto }
    \printto }

    where we have made use of the Texture2D and RenderTargetOutput types to create a
    destination texture and attach it as the output of the Scene2D renderer.

    Next, we tell the Scene2D object which entities may feed it input events and we
    initially disable the handling of mouse events:

    \printto mouseEnabled: false

    Finally, we can specify the Qt Quick scene to render by adding a custom QML component
    as a child to the Scene2D element:

    \skipto LogoControls
    \printuntil }
    \printuntil }

    When the mouseEnabled property is set to true by the ObjectPicker, then the Scene2D
    object will process mouse events from any ObjectPickers attached to the listed entities.
    In this way, you have the freedom to use the texture generated by the Scene2D object in
    any way you wish, even on more than one Entity.

    The \e LogoControls.qml file is just a regular Qt Quick 2 scene which in this case
    also makes use of the Qt Quick Controls components.
*/