Hi Gunnar, On Tue, May 27, 2014 at 10:36 AM, Gunnar Sletta <gunnar.sle...@jolla.com> wrote:
> > On 27 May 2014, at 10:28, Jacob Kroon <jacob.kr...@gmail.com> wrote: > > > Hi Gunnar, > > > > On Fri, May 23, 2014 at 11:39 AM, Gunnar Sletta <gunnar.sle...@jolla.com> > wrote: > > > > On 23 May 2014, at 10:32, Jacob Kroon <jacob.kr...@gmail.com> wrote: > > > > > Hi, > > > > > > I'm experimenting with a Qt application running on the Wandboards, > > > at full hd resolution, 1920x1080x32. I have a static background image, > and some small animated Qml-elements on the screen. I'm not entirely > satisfied with the resulting performance, and I think it is because of the > background image being constantly fully redrawn in each frame. > > > > If it cannot render a single image at that resolution, then it is not a > suitable hardware for that resolution :) > > > > If this is the case your options are to reduce the bit depth, reduce the > resolution or reduce the framerate (such as going for 30FPS instead of > 60FPS) > > > > Is the image alpha blended? If it is a JPEG it should be opaque, but if > it is a PNG it will most likely have an alpha channel (even thought it > really doesn't. I know, stupid, but that how it is). For some GPUs blending > can add a bit of overhead, and doing it fullscreen can be what tips the > balance. > > > > > > For the background image, what I did was that I used a tiled noise > image, and did a radial blend on it. The resulting image was cached though. > But yes, the resulting image showed up as "alpha" in the renderer debug > output, I've switched to having a static prepared png image, and now the > background image shows up as "opaque". > > > > > I've experimented with > > > > > > * setClearBeforeRendering(false), since the background will be drawn > anyway, there is no point in clearing before rendering. This seemed to have > little impact on performance though. > > > > The effect of turning off clearing is highly hardware dependent. Some > drivers/GPUs will benefit from not clearing as the clear is just yet > another pass over all pixels. Others will use the clear as an indication of > "new frame" and will have to do all manner of nasty stuff, like storing the > depth buffer into system memory because you didn't clear it before the > frame began. > > > > See the performance guidelines of your GPU for the actual recommendation > for your chip. > > > > > > It seems that setting "QSG_ANTIALIASING_METHOD=msaa" gives a huge > improvement on the cpu usage. > > That is a bit interesting... What are you drawing on top of this image? > msaa based antialiasing generally adds a bit to the cost on the GPU, but it > makes the work a lot simpler for the renderer when you have Rectangle and > Image elements with antialiasing: true in QML. > > Is there a lot of overdrawing? > > Yes, I think is exactly what I saw, when I enabled msaa the number of vertexes sent to the gpu dropped, and lowered the cpu usage. Indeed I am doing some overdrawing, that I probably can work around somehow. I'm still pretty knew to qml. > > Also, playing with QSG_RENDERER_BATCH_VERTEX_THRESHOLD and > QSG_RENDERER_BATCH_NODE_THRESHOLD, > > allows me to lower the cpu usage even further. Still, the background > image is taking a considerable time it seems. With bg image I get ~27 fps, > > without it I get ~85 fps (with vsync turned off) > > How is the performance if you use an image which is a lot smaller? Since > the big image causes such a big impact, maybe texture loading is a > bottleneck. If this is the problem, then using a ShaderEffect to create the > tiled-noise background might be an option as that would then not suffer > from massive texture fetching. > > A smaller image that I scale up seems to improve performance as well. However, I'm not sure if generating the tiled-noise using a shader would improve things on the Wandboard, I did try the qt5-launch-demo, normal and simple version, and the one without the tiled-noise bg ran a lot smoother. Thanks /Jacob
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