[Interest] Qt3D Rendering offscreen

[Andy]

Does anybody have any hints? I've tried all kinds of node configurations
and can't get this to work.

Thanks.

---
Andy Maloney  //  https://asmaloney.com
twitter ~ @asmaloney <https://twitter.com/asmaloney>


On Sat, Aug 12, 2017 at 2:03 PM, Andy <asmaloney at gmail.com> wrote:

> Based on your outline, here is the hierarchy I have set up (but I still
> get images of size (1,1)):
>
> Qt3DRender::QRenderCapture::
>     Qt3DExtras::QForwardRenderer::
>         Qt3DRender::QRenderSurfaceSelector::
>             Qt3DRender::QViewport::
>                 Qt3DRender::QCameraSelector::
>                     Qt3DRender::QClearBuffers::
>                         Qt3DRender::QFrustumCulling::
>         Qt3DRender::QFilterKey::
>         Qt3DRender::QRenderTargetSelector::
>             Qt3DRender::QRenderTarget::
>                 Qt3DRender::QRenderTargetOutput::
>                     Qt3DRender::QTexture2D::
>                 Qt3DRender::QRenderTargetOutput::
>                     Qt3DRender::QTexture2D::
>
> Am I attaching things in the right place?
>
> This is how I'm creating it:
>
>    const QSize cTargetSize( 1024, 768 );
>
>    m_forwardRenderer->setExternalRenderTargetSize( cTargetSize );
>
>    Qt3DRender::QTexture2D  *color0Texture = new Qt3DRender::QTexture2D;
>    color0Texture->setSize( cTargetSize.width(), cTargetSize.height() );
>    color0Texture->setFormat( Qt3DRender::QAbstractTexture::RGBA32F );
>    color0Texture->setGenerateMipMaps( false) ;
>
>    Qt3DRender::QTexture2D  *depthTexture = new Qt3DRender::QTexture2D;
>    depthTexture->setSize( cTargetSize.width(), cTargetSize.height() );
>    depthTexture->setFormat( Qt3DRender::QAbstractTexture::D32F );
>    depthTexture->setGenerateMipMaps( false );
>
>    Qt3DRender::QRenderTargetOutput  *colorOutput = new Qt3DRender::
> QRenderTargetOutput;
>    colorOutput->setTexture( color0Texture );
>    colorOutput->setAttachmentPoint( Qt3DRender::QRenderTargetOutput::Color0
> );
>
>    Qt3DRender::QRenderTargetOutput  *depthOutput = new Qt3DRender::
> QRenderTargetOutput;
>    depthOutput->setTexture( depthTexture );
>    depthOutput->setAttachmentPoint( Qt3DRender::QRenderTargetOutput::Depth
> );
>
>    Qt3DRender::QRenderTarget  *renderTarget = new
> Qt3DRender::QRenderTarget;
>    renderTarget->addOutput( colorOutput );
>    renderTarget->addOutput( depthOutput );
>
>    Qt3DRender::QRenderTargetSelector   *renderTargetSelector = new
> Qt3DRender::QRenderTargetSelector( m_forwardRenderer );
>
>    renderTargetSelector->setTarget( renderTarget );
>
>    m_forwardRenderer->setParent( mRenderCapturer );
>    m_renderSettings->setActiveFrameGraph( mRenderCapturer );
>
>
> ---
> Andy Maloney  //  https://asmaloney.com
> twitter ~ @asmaloney <https://twitter.com/asmaloney>
>
>
> On Sat, Aug 12, 2017 at 8:58 AM, Andy <asmaloney at gmail.com> wrote:
>
>> On Sat, Aug 12, 2017 at 8:40 AM, Sean Harmer <sean.harmer at kdab.com>
>> wrote:
>>
>>> Hi,
>>>
>>> On Friday 11 August 2017 14:34:34 Andy wrote:
>>> > Goal: With Qt3D (C++), render my scene offscreen, use render capture
>>> on it,
>>> > and save image to disk.
>>> >
>>> > With my Qt3DWindow-based solution the scene looks fine and I can do the
>>> > render capture part (on macOS anyways - Windows doesn't work for me -
>>> > https://bugreports.qt.io/browse/QTBUG-61223 ).
>>> >
>>> > Now I need to be able to do it offscreen (without the window open).
>>> >
>>> > I thought this was going to be as simple as setting a
>>> QOffscreenSurface as
>>> > my forward renderer surface - something like:
>>> >
>>> >    QOffscreenSurface *surface = new QOffscreenSurface;
>>> >
>>> >    surface->create();
>>> >
>>> >    Qt3DExtras::QForwardRenderer  *forwardRenderer = new
>>> > Qt3DExtras::QForwardRenderer;
>>> >
>>> >    forwardRenderer->setSurface( surface );
>>> >    forwardRenderer->setExternalRenderTargetSize( QSize( 800, 600 ) );
>>> >
>>> >    qDebug() << surface->format() << surface->size() <<
>>> surface->isValid();
>>> >
>>> > While this gives me a valid surface and the format is correct, its
>>> size is
>>> > always (1,1) and the render capture gives me images of that size.
>>> >
>>> > How do I set the size of the QOffscreenSurface?
>>>
>>> You don't :) An offscreen surface is only good for making a GL context
>>> current. It is not suitable as a render target. If you want to do
>>> offscreen
>>>
>>
>> I guess I find that class name confusing then... One draws on a surface,
>> right? :-)
>>
>> rendering with QOffscreenSurface, you will need to provide your own render
>>> target in the form of a framebuffer object.
>>>
>>> You will need to create an FBO by way of a QRenderTarget with a 2D
>>> texture of
>>> the desired size attached to the color0 attachment point, and a depth
>>> format
>>> texture of the same size attached to the depth attachment point.
>>>
>>
>> So that's a QTexture2D for colo0 and... what for the "depth format
>> texture"? Another QTexture2D?
>>
>>
>>>
>>> Select this with a QRenderTargetSelector in a custom framegraph to direct
>>> rendering into the attached textures. You can then do a pixel read back
>>> operation with the QRenderCapure and save the resulting image.
>>>
>>
>> You make it sound so easy!
>>
>>
>>> I suppose this could be wrapped in a convenience that allows the rest of
>>> the
>>> framegraph beyond the render target selector and render capture to be
>>> set.
>>>
>>
>> +1. If I ever get anything working, I'd be happy to work with someone to
>> get it into shape for Qt3DExtras.
>>
>> Thanks Sean!
>>
>>
>>> Cheers,
>>>
>>> Sean
>>>
>>> >
>>> > Or am I going about this the wrong way?
>>> >
>>> > (It would be nice to have a class like the Qt3DWindow one specifically
>>> for
>>> > offscreen rendering.)
>>> >
>>> > ---
>>> > Andy Maloney  //  https://asmaloney.com
>>> > twitter ~ @asmaloney <https://twitter.com/asmaloney>
>>>
>>> --
>>> Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
>>> Klarälvdalens Datakonsult AB, a KDAB Group company
>>> Tel. UK +44 (0)1625 809908, Sweden (HQ) +46-563-540090
>>> KDAB - Qt Experts - Platform-independent software solutions
>>>
>>
>> ---
>> Andy Maloney  //  https://asmaloney.com
>> twitter ~ @asmaloney <https://twitter.com/asmaloney>
>>
>
>
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