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  1. Qt
  2. QTBUG-91031

Opaque Items missing from QQuickView render target FBO

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: P2: Important
    • Resolution: Out of scope
    • Affects Version/s: 5.12.10
    • Fix Version/s: None
    • Component/s: Quick: SceneGraph
    • Labels:
      None
    • Environment:
      Qualcomm S820, AGL linux.

      Description

      Our application handles QQuickView::afterRendering signal to add post processing for frames .

      Observations:

      QML Items having opacity=1.0 aren't displayed if the post processing is enabled.
      QML Items which have opacity<1.0 (for e.g 0.99) are drawn successfully.

       


      Post processor creates a new FBO with color and depth components attached.

      We are providing this FBO to QML using QQuickView::setRenderTarget.

      Our expectations is “QML will render everything in this buffer and will able to apply our shader to this color texture”.

      It works for simple scene graphs and for the Qt 3D Studio presentations but doesn’t work for the complex scene in QML.

      We assume something may happen for loader component which we actively using.

      For example opaque parts was drawn in separate step and QML render draws it in some cases outside of FBO bind into color buffer glBindFramebuffer(GL_FRAMEBUFFER, 0)

      After this renderTarget FBO binds and transparent parts comes into it.

      In regular case transparent parts will be blended with opaque data from the previous step.

      Simple scheme:

      Expected

      (FBO bind) > (Opaque step) -> (Transparent step) -> (PostProcessor)>(swapBuffers)

      Actual for complex cases

      (Opaque step) > (FBO bind) -> (Transparent step) -> (PostProcessor)>(swapBuffers)

       

       

        Attachments

        1. Elina.jpeg
          Elina.jpeg
          545 kB
        2. Log_QSG_INFO.txt
          41 kB
        3. Rectangles.zip
          582 kB
        4. Windows.png
          Windows.png
          12 kB
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          Activity

            People

            Assignee:
            qt.team.graphics.and.multimedia Qt Graphics Team
            Reporter:
            e0150566 Janne Koskinen
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            0 Vote for this issue
            Watchers:
            6 Start watching this issue

              Dates

              Created:
              Updated:
              Resolved:

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