Render QML as a texture/material inside another QML

RobertB

Hello,

I am using Qt 6.6.0 with OpenGL.

Is it possible to render a QML instance to a texture, and expose that texture to a totally different QML instance that uses Quick3D. Because then I can use the texture as a material on a Model inside View3D.

Something like this:

Create a QQmlApplicationEngine or QQmlEngine or QQmlContext and load some simple .qml
Render this to a framebuffer (how?)
Get a texture from this framebuffer (how?)
Pass this texture to a totally new QML instance that loads some .qml (how?)
Use this texture as a material on a 3D Model

Any tips / links to documentation welcome.

johngod

@RobertB Hi
You can do that with grabToImage, see here https://doc.qt.io/qt-6/qml-qtquick-item.html#grabToImage-method

RobertB

@johngod Thanks. I was thinking about doing something with a framebuffer because I suspect grabToImage() is slow if it is repeatedly called at the monitor's vsync.

Perhaps an easier question is "how to apply a QOffscreenSurface to a Model" (in combination with QQuickRenderControl).

For example, given this QML code:

View3D {
    id: view
    anchors.fill: parent

    Model {
        id: test
        position: Qt.vector3d(0, 0, 0)
        scale: Qt.vector3d(1, 1, 1)
        source: "#Rectangle"

        materials: [
            DefaultMaterial {
                diffuseColor: "red"
            }
        ]
    }

    PerspectiveCamera {
        position: Qt.vector3d(0, 0, 250)
        eulerRotation.x: 0
    }

    DirectionalLight {
        eulerRotation.x: -30
        eulerRotation.y: -70
    }
    
    environment: SceneEnvironment {
        backgroundMode: SceneEnvironment.Color
        clearColor: "skyblue"
    }
}

How to apply a QOffscreenSurface to the materials property of Model test. Is it possible? Or perhaps, how to use a fbo as a material?

KH-219Design

Caveat: I have never done any 3d coding work beyond compiling the Qt3d samples! So I probably won't have much more to say after this post.

My post to you, is:

Does this example do what you want? I think this example might give some clues or point in the right direction: https://doc.qt.io/qt-5/qt3d-scene2d-example.html

KH-219Design

The link to the example also exists for Qt6. https://doc.qt.io/qt-6.2/qt3d-scene2d-example.html

RobertB

@KH-219Design that actually looks like what I want, ill check it out, thanks!