[Interest] Drawing dashed line with QSGSimpleMaterialShader

[Gunnar Sletta]

When you rotate or scale a texture it will no longer align with the destination pixels perfectly, so you some artifacts expected. You can set the texture's filtering to QSGTexture::Linear to make use bilinear sampling to minimize much of these, but if you want it "perfect" you will have to rasterize the source image in device coordinates rather than logical ones.

cheers,
Gunnar

> On 13 Jun 2016, at 22:37, Artem Fedoskin <afedoskin3 at gmail.com> wrote:
> 
> Thank you guys for all your advices.
> 
> I implemented the thing I need by drawing textures with QPainter but whenever I rotate my QQuickItem using setRotation() or rotate the transform matrix the texture is displayed incorrectly.
> 
> This is the correct way of displaying - http://i.imgur.com/bZIsWHR.png
> And an incorrect one - http://i.imgur.com/63y21up.png
> 
> What should be done to get texture displayed as on the first pic while rotating the matrix of QSGTransformNode or rotating QQuickItem?
> Switching antialiasing on and off doesn't change the situation.
> 
> Regards, Artem
> 
> 
> 2016-06-06 18:24 GMT+02:00 Shawn Rutledge <Shawn.Rutledge at qt.io>:
> 
> > On 6 Jun 2016, at 12:29, Gunnar Sletta <gunnar at sletta.org> wrote:
> >
> >> On 06 Jun 2016, at 09:27, Artem Fedoskin <afedoskin3 at gmail.com> wrote:
> >> Another question - is there any way to draw text solely in Scene Graph using QSG classes? I need to draw a lot of text labels and what only came to my mind is to draw them using QPainter on a QImage and store it as a QSGSimpleTextureNode in the node itself.
> >
> > Nope, the text API is all internally, unfortunately. Going through the QImage + texture node code path shouldn't be too bad though.
> 
> It’s not impossible to put text into the scenegraph from C++, but you will need to use private APIs, so you will be tied to a range of Qt versions where those private APIs don’t change.  You can use QTextLayout to generate QGlyphRuns, and create a QSGGlyphNode for each.  Some other QSG stuff is public (and there are examples in qtdeclarative/examples/quick/scenegraph), but QSGGlyphNode isn't.
> 
> It may turn out that rendering textures with QPainter, as you suggest, is faster anyway.
> 
> 
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