Dimitri Frederickx wrote:
> The reason that I want to use OpenGL for rendering is SVG. I have some large
> animated SVG files I want to show in high definition. When I don't use
> OpenGL,
> my animations are not fluent. From time to time the animation stops for a few
> milli seconds, and then going further but dropping some intermediate
> rendering.
>
That sounds like garbage collection kicking in to me, but in that case I
suppose the effect should be the same regardless of the viewport widget.
Have you tried removing all allocations in the inner loop, though?
> Can someone help me?
>
> Problems with OpenGL:
>
> 1. By using OpenGL, the quality of my graphics items is drastically reduced.
> When I resize my pixmaps, I'm using SmoothTransform. Without OpenGL my
> pictures
> look really nice and smooth, but with OpenGL I see little blocks around my
> pictures, no smooth lines, etc. How can I increase the quality of my items?
>
I'm not completely clear on what is happening here. Are you using
QGraphicsPixmapItems? If you are, you should set SmoothTransform on the
items:
myPixmapItem.setTransformationMode(Qt.TransformationMode.SmoothTransformation);
If you are however using your own QGraphicsItem subclass with an
overridden paint() method in which you call drawPixmap() on a painter,
then you should either set SmoothPixmapTransform render hint on the
painter before drawing, or on the entire graphics view if you want this
as a global setting:
myGraphicsView.setRenderHint(QPainter.RenderHint.SmoothPixmapTransform);
This should, however, give the same results for OpenGL as for software
rendering. I have made an attempt at reproducing your problem on
Windows, but I don't see any major differences between a scene rendered
with OpenGL and one rendered without here.
A few questions to try to track down the problem:
1. Have you tested this on any other platform than Windows?
2. Do you see any artifacts when running the 40 000 chips demo and
turning on OpenGL rendering? Some differences between software and
hardware rendering is to be expected, especially for font rendering, and
this might be affected by the graphics drivers or the graphics hardware
you are running. We don't know of any issues we would consider
"unusable", though.
3. Which graphics hard ware are you using?
4. Could you possibly send us screenshots of the problems you are
seeing, and also a code example if you have one? Since I haven't been
able to reproduce this, it's hard to picture how bad it is.
> 2. I have made a marquee (scrolling text) with the use of QGraphicsTextItem
> and
> QGraphicsItemAnimation. Without OpenGL this works smooth, but with OpenGL my
> text looks ugly because of the poor quality and because the scrolling
> suddenly
> doesn't happen as smooth as before.
>
I'm not sure, but this may be a side effect of how text rendering is
optimized in our OpenGL engine. You could replace the regular text
rendering with an algorithm which converts the texts to QPainterPaths
(see the Deformation demo) and then renders this instead to avoid the
problems. Any transformation on the text should be smooth then, but the
performance will suffer accordingly.
> 3. Adding the setViewport line in my code makes my application crash when I
> quit
> it. 9 out of the 10 times my application crashes on a shutdown. When I don't
> set
> the viewport, everything works just fine. Here is a part of the error dump:
>
I've reproduced this crash and made a task for fix it for Qt Jambi 4.4.0_01.
-- Eskil
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