On Mon, Sep 3, 2018 at 9:25 AM Paul Lemire <paul.lem...@kdab.com> wrote:
> Glad to hear that, hopefully things are starting to make more sense now.
>
Getting there - thank you!
On 09/03/2018 02:54 PM, Andy wrote:
>
> Progress! Here's my current framegraph:
>
> [snip]
>
> Question:
>
> 1) I am using an RGBAFormat for my texture. I changed the alpha in the
> clear colour from 0x80 to 0xEE and I now see an alpha cleared background in
> the offscreen (see image). I can just use RGB for my purposes right now,
> but I'm curious why the onscreen clearing is not using the alpha channel? I
> can confirm this by changing the clear colour to #FF000000 - I just get
> solid black.
>
> Well I believe that this depends on the format of your back buffer
> (usually it is RGB). You can try to query it with
> QSurfaceFormat::defaultFormat() and looking for the alphaBuffer size (or
> apitrace also gives you the format when you select a draw call that renders
> to screen).
>
Got it! If I setAlphaBufferSize( 8 ) on my default format it works.
>
> Problem:
>
> 1) The resulting scene isn't the same in the offscreen capture:
> - the yellow cube is on top of everything
> - the red & blue arrows aren't clipped by the plane
>
> I suspect that this is caused by the fact that you have no depth
> attachment on your RenderTarget so that depth testing isn't performed
> properly. You would need to create another RenderTargetOutput that you bind
> to the attachment point Depth with a suitable Texture2D texture with format
> (D32, D24 ...).
>
Bingo. That fixes it.
> - it isn't antialiased
>
> That's likely caused by a) not having a high resolution enough for your
> attachments b) using a Texture2D instead of a Texture2DMultisample (though
> I'm not sure RenderCapture would work with the latter).
>
Have you tried going for a 2048/2408 texture instead of 512/512 assuming
> you have no memory constraints? Then you can always scale back the QImage
> you capture to 512/512 if need be.
>
Texture2DMultisample does indeed make it better. Once I set "samples" to
the same as my QSurfaceFormat::defaultFormat(), I get decent results. Not
100% the same, but very close. (So it does work w/RenderCapture!)
My "final" frame graph (for those following along):
RenderSurfaceSelector:
Viewport:
ClearBuffers:
buffers: ColorDepthBuffer
clearColor: "#faebd7"
NoDraw: {}
FrustumCulling:
# OnScreen
CameraSelector:
objectName: onScreenCameraSelector
RenderCapture:
objectName: onScreenCapture
# OffScreen
CameraSelector:
objectName: offScreenCameraSelector
RenderTargetSelector:
target:
RenderTarget:
attachments:
- RenderTargetOutput:
attachmentPoint: Color0
texture:
Texture2DMultisample:
objectName: offScreenTexture
width: 1024
height: 768
format: RGBFormat
samples: 8
- RenderTargetOutput:
attachmentPoint: Depth
texture:
Texture2DMultisample:
width: 1024
height: 768
format: D24
samples: 8
ClearBuffers:
buffers: ColorDepthBuffer
clearColor: "#faebd7"
NoDraw: {}
RenderCapture:
objectName: offScreenCapture
If anyone is interested in the code to read framegraphs as YAML like this,
please get in touch and I can clean it up & put on gitlab (sometime next
month). It makes it a lot easier to iterate on building a framegraph. It
also drastically reduces the amount of boilerplate code, you can include &
read them as resources, and you don't have to bring in all of QML.
Now that I have the basics working... I'll need to dig into the multipass
shader stuff to get the effects I want.
Thank you for your patience!
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