QQuickFramebufferObject and offscreen rendering



  • I'm working with a project that uses QQuickFramebufferObject and QQuickFrambufferObject::Renderer classes to render to the screen. I'm wondering if there are any examples which show how to do offscreen rendering using QQuickFramebufferObject?

    I've tried a few approaches -- either a manually-created FBO or a QT-abstracted FBO (like creating a separate QQuickFramebufferObject or a QOpenGLFrameBufferObject), and I run into a problem when I unbind that offscreen FBO (so that I can render to the normal frame buffer). Specifically, I get a solid blue framebuffer on-screen that shows nothing else.

    Since I'm not allowed to share this code I was wondering if anyone has done offscreen rendering with QQuickFramebufferObject. The examples I find use the QOpenGLWidget pattern instead.



  • Here's an attempt of me trying to do so (using the fboinsgrenderer example):
    https://github.com/sohailshafii/textureinsgnode_offscreen/blob/master/fboinsgrenderer.cpp

    There is a section of the code where I try to use an offscreen buffer, commented out because it causes the normal frame buffer to render as blue:
    // uncomment this block of code to see an incorrect rendering
    /m_fbo->bind();
    logo.render();
    update();
    m_fbo->release();
    m_fbo->bindDefault();
    /
    logo.render();
    update();

    I don't know why I can't seem to use an offscreen fbo with a QtQuickFramebufferObject renderer.


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