- 
    Bug 
- 
    Resolution: Unresolved
- 
    P2: Important 
- 
    None
- 
    6.6.0
- 
    None
If you use compositingMode and set it to Scene3D.Underlay instead of FBO, Qt3D with RHI backend will draw white
    Scene3D {
        id: sceneId
        anchors.fill: parent
        focus: true
        aspects: ["render", "input", "logic"]
        entity: rootEntity
        compositingMode: Scene3D.Underlay
    }
The result of Scene3D.Underlay

What's expected:

Looking at the Qt3D source code, it doesn't currently support underlay.
const bool usesFBO = scene3DRenderer->m_compositingMode == Scene3DItem::FBO; // Not sure how we could support underlay rendering properly given Qt3D RHI will render into its own // RHI RenderPasses prior to QtQuick and beginning a new RenderPass clears the screen Q_ASSERT(usesFBO);
The application should have asserted here, but it doesn't. Supporting underlay with RHI seems possible given there's a Qt example about it: https://doc.qt.io/qt-6/qtquick-scenegraph-rhiunderqml-example.html
I've attached a demo program that shows the issue.


