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  1. Qt
  2. QTBUG-69985

Scene3D (and Studio3D) needs a way to determine if the Qt 3D scene changes

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      The way Scene3D (and all similar solutions like Studio3D or even the upcoming future Studio3DEngine+Layer3D combo) works is highly not ideal for 3D scenes that are not constantly changing.

      Marking the node as dirty and scheduling a Quick re-render by calling QQuickWindow::update() on each and every frame (this is hooked up to QQuickWindow::beforeRendering) is wasteful (performance, power) and is not acceptable to some customers. Qt Quick itself does not have this problem: if nothing changes in the Qt Quick scene (e.g. all animations stop) the render loop will not render anything.

      So Scene3DRenderer::render() (and all similar solutions in Studio3D and elsewhere) would need a way to tell if rendering needs to be done:

      if (renderAspectPrivate->needsRender()) {
    // ... set up fbo, call renderSynchronous, etc.
    node->markDirty(DirtyMaterial);
    m_window->update();
}
// else do nothing, no dirty, no update

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            zakalawe James Turner
            lagocs Laszlo Agocs
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              Created:
              Updated:
              Resolved:

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