Qt3D: Antialising in deferred rendering

  • Hello all,

    I am writing an application in which I want to use deferred rendering.

    When using forward rendering, we can see that multisample antialiasing (MSAA) is enabled.
    However, I am trying to have MSAA in my deferred rendering application and I am not able to do this.

    As my framegraph is pretty complex (see below), I just show important parts of my code where I have tried to enable MSAA.

    • First of all, I have followed the answer of this topic before creating the Qt3DWindow.
    • Then, in my framegraph I have enabled MSAA by adding a QMultiSampleAntiAliasing in the QRenderStateSet
        auto globalRenderStateSet = new Qt3DRender::QRenderStateSet(viewport);
        auto depthTestState = new Qt3DRender::QDepthTest();
        depthTestState -> setDepthFunction(Qt3DRender::QDepthTest::LessOrEqual);
        auto msaaState = new Qt3DRender::QMultiSampleAntiAliasing();
        globalRenderStateSet -> addRenderState(depthTestState);
        globalRenderStateSet -> addRenderState(msaaState);
    • I have a GBuffer (QRenderTarget) in which I use only QTexture2DMultisample objects, all with the same amount of samples (the same as in the QSurfaceFormat of the first point as well).
        _textures = new Qt3DRender::QTexture2DMultisample*[attachmentsCount];
        _attachments = new Qt3DRender::QRenderTargetOutput*[attachmentsCount];
        for (int attachmentIndex = 0 ; attachmentIndex < attachmentsCount ; attachmentIndex++)
            const TargetOutputParameters& parameter = parameters[attachmentIndex];
            _attachments[attachmentIndex] = new Qt3DRender::QRenderTargetOutput(this);
            _textures[attachmentIndex] = new Qt3DRender::QTexture2DMultisample();
            _textures[attachmentIndex] -> setFormat(parameter.format());
            _textures[attachmentIndex] -> setWidth(TextureWidth);
            _textures[attachmentIndex] -> setHeight(TextureHeight);
            _textures[attachmentIndex] -> setGenerateMipMaps(false);
            _textures[attachmentIndex] -> setWrapMode(Qt3DRender::QTextureWrapMode(Qt3DRender::QTextureWrapMode::ClampToEdge));
            _textures[attachmentIndex] -> setMinificationFilter(Qt3DRender::QAbstractTexture::Linear);
            _textures[attachmentIndex] -> setMagnificationFilter(Qt3DRender::QAbstractTexture::Linear);
            _textures[attachmentIndex] -> setSamples(8);
            _attachments[attachmentIndex] -> setTexture(_textures[attachmentIndex]);
            _attachments[attachmentIndex] -> setAttachmentPoint(parameter.attachmentPoint());
            _attachments[attachmentIndex] -> setObjectName(parameter.name());
    • I have another QRenderTarget (MSAADestinationRenderTarget) in which I only have QTexture2D objects. I perform a QBlitFramebuffer to copy the MSAA color texture into the single-sample render target.
                auto noDraw = new Qt3DRender::QNoDraw(cameraSelector);
                auto sceneBlitColorFBOs = new Qt3DRender::QBlitFramebuffer(noDraw);
                _gBuffer = new GBuffer();
                _msaaRenderTarget = new MSAADestinationRenderTarget();
                auto msaaRenderTargetSelector = new Qt3DRender::QRenderTargetSelector(cameraSelector);
                msaaRenderTargetSelector -> setTarget(_msaaRenderTarget);
                sceneBlitColorFBOs -> setSource(_gBuffer);
                sceneBlitColorFBOs -> setSourceAttachmentPoint(Qt3DRender::QRenderTargetOutput::Color0);
                sceneBlitColorFBOs -> setSourceRect(QRect(0, 0, _view -> width(), _view->height()));
                sceneBlitColorFBOs -> setDestination(_msaaRenderTarget);
                sceneBlitColorFBOs -> setDestinationAttachmentPoint(Qt3DRender::QRenderTargetOutput::Color0);
                sceneBlitColorFBOs -> setDestinationRect(QRect(0, 0, _view -> width(), _view->height()));

    All of this seems to be working well as I can display this texture on a quad and see the scene, move the camera, etc. But, it is not antialiased.

    Am I missing something?
    Thank you for any help.



  • Hi,

    I have not found any solution from C++ code itself.
    So I have implemented FXAA into my fragment shader to get an antialiased picture.


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